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8/19/2015
MODULE 12.1 OVERVIEW OF THE
CENTRAL NERVOUS SYSTEM
ERIN C. AMERMAN
FLORIDA STATE COLLEGE AT JACKSONVILLE
Lecture Presentation by Suzanne Pundt
University of Texas at Tyler
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CENTRAL NERVOUS SYSTEM
OVERVIEW OF CNS FUNCTIONS
• Central nervous system (CNS) – includes brain and
• Functions of nervous system can be broken down into
spinal cord; involved in movement, interpreting
sensory information, maintaining homeostasis, and
functions relating to mind
three categories:
 Motor functions – include stimulation of a muscle cell
contraction or a gland secretion; function of peripheral
nervous system (PNS)
 Sensory functions – detection of sensations within and
outside body; also is a function of PNS
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OVERVIEW OF CNS FUNCTIONS
 Integrative functions – include decision-making
processes; exclusive function of CNS; includes a wide
variety of functions:
o
o
o
BASIC STRUCTURE OF THE BRAIN
AND SPINAL CORD
•
• Functions of nervous system (continued):
o
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Interpretation of sensory information
Planning and monitoring movement
Maintenance of homeostasis
Higher mental functions such as language and learning
Brain – soft, whitish-gray organ, anatomically continuous
with spinal cord; resides in cranial cavity and directly or
indirectly controls most of body’s functions
 Weighs between 1250 and 1450 grams; made of mostly
nervous tissue; contains epithelial and connective tissues as
well
 Internal cavities called ventricles; filled with cerebrospinal
fluid
 Receives about 20% of total blood flow during periods of
rest; reflects its requirements for huge amounts of oxygen,
glucose, and nutrients
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BASIC STRUCTURE OF THE BRAIN
AND SPINAL CORD
BASIC STRUCTURE OF THE BRAIN
AND SPINAL CORD
• Brain consists of four divisions, each distinct in type of
• Cerebrum – enlarged superior portion of brain;
input it receives and where it sends its output:
 Cerebrum
divided into left and right cerebral hemispheres
 Each cerebral hemisphere is further divided into five
lobes containing groups of neurons that perform specific
tasks
 Diencephalon
 Cerebellum
 Responsible for higher mental function such as learning,
memory, personality, cognition (thinking), language, and
conscience
 Brainstem
 Performs major roles in sensation and movement as well
Figure 12.1 Divisions of the brain (lateral view).
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BASIC STRUCTURE OF THE BRAIN
AND SPINAL CORD
BASIC STRUCTURE OF THE BRAIN
AND SPINAL CORD
• Diencephalon – deep underneath cerebral
• Cerebellum – posterior and inferior portion of brain
hemispheres; central core of brain
 Divided into left and right hemispheres
 Consists of four distinct structural and functional parts
 Responsible for processing, integrating, and relaying
information to different parts of brain, homeostatic
functions, regulation of movement, and biological
rhythms
 Heavily involved in planning and coordination of
movement, especially complex activities such as playing
a sport or an instrument
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BASIC STRUCTURE OF THE BRAIN
AND SPINAL CORD
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BASIC STRUCTURE OF THE BRAIN
AND SPINAL CORD
• Brainstem – connects brain to spinal cord
 Involved in basic involuntary homeostatic functions
 Control of certain reflexes
 Monitoring movement
 Integrating and relaying information to other parts of
nervous system
Figure 12.1 Divisions of the brain (lateral view).
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BASIC STRUCTURE OF THE BRAIN
AND SPINAL CORD
BASIC STRUCTURE OF THE BRAIN
AND SPINAL CORD
• Spinal cord – long tubular organ enclosed within
• White matter – found in both brain and spinal cord;
protective vertebral cavity; blends with inferior
portion of brainstem; ends between first and second
lumbar vertebrae
 43–46 cm (17–18 inches) in length and only ranges from
0.65–1.25 cm (0.25–0.5 inches) in diameter
 Central canal – an internal cavity within spinal cord
that is continuous with brain’s ventricles; filled with
cerebrospinal fluid
consists of myelinated axons
 Each lobe of cerebrum contains bundles of white matter
called tracts; receives input from and sends output to
clusters of cell bodies and dendrites in cerebral gray
matter called nuclei (Figure 12.2a)
 Spinal cord contains white matter tracts that shuttle
information processed by nuclei in spinal gray matter
(Figure 12.2b)
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BASIC STRUCTURE OF THE BRAIN
AND SPINAL CORD
BASIC STRUCTURE OF THE BRAIN
AND SPINAL CORD
• Gray matter – found in both brain and spinal cord;
• Communication between gray and white matter
consists of neuron cell bodies, dendrites, and
unmyelinated axons
 Outer few millimeters of cerebrum is gray matter; deeper
portions of brain are mostly white matter with some gray
matter scattered throughout
 Spinal cord is mostly gray matter that processes
connects different regions of brain and spinal cord with
one another; myelinated axons enable near
instantaneous communication between locations
• Make note – organization of gray and white matter in
brain and spinal cord is reversed; spinal white matter is
superficial while it is deep in brain
information (in cord center); surrounded by tracts of
white matter (outside); relays information to and from
brain
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BASIC STRUCTURE OF THE BRAIN
AND SPINAL CORD
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OVERVIEW OF CNS
DEVELOPMENT
• Brain and spinal cord develop from a tube with an
enlarged end in embryo and fetus (Figure 12.3)
 Neural tube – hollow tube from which nervous tissue
develops; completely developed by fourth week of
gestation
 Caudal end of neural tube forms spinal cord; cranial end
forms three saclike structures (primary brain vesicles)
which include forebrain, midbrain, and hindbrain
 Cavity within hollow neural tube becomes ventricles in
brain and central canal in spinal cord
Figure 12.2 White and gray matter in the CNS.
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OVERVIEW OF CNS
DEVELOPMENT
OVERVIEW OF CNS
DEVELOPMENT
• Primary brain vesicles give rise to five secondary
brain vesicles by fifth week of development
• Secondary brain vesicles create four divisions of
mature brain (continued):
• Secondary brain vesicles create four divisions of
 Midbrain expands into secondary brain vesicle called
mesencephalon; develops into mature midbrain
mature brain:
 Forebrain expands into two secondary brain vesicles
(telencephalon and diencephalon); two lobes of
telencephalon become cerebral hemispheres;
diencephalon retains its name in mature brain
 Hindbrain develops into two secondary brain vesicles
(metencephalon and myelencephalon), both of which
develop into remainder of brainstem; metencephalon
also matures to become cerebellum
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OVERVIEW OF CNS
DEVELOPMENT
MODULE 12.2 THE BRAIN
Figure 12.3 Development of the brain.
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THE CEREBRUM
THE CEREBRUM
• Cerebrum – structure responsible for higher mental
functions (Figures 12.4–12.9, Table 12.1)
 Gross anatomical features of cerebrum include:
o
Sulci – shallow grooves on surface of cerebrum; gyri –
elevated ridges found between sulci; together increase surface
area of brain; maximizing limited space within confines of
skull; example of Structure-Function Core Principle
 Gross anatomical features (continued):
o
Fissures – deep grooves found on surface of cerebrum
o
Longitudinal fissure – long deep groove that separates left and
right cerebral hemispheres
o
A cavity is found deep within each cerebral hemisphere; right
hemisphere surrounds right lateral ventricle; left hemisphere
surrounds left lateral ventricle
Figure 12.4 Structure of the cerebrum.
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THE CEREBRUM
THE CEREBRUM
• Five lobes are found in each hemisphere of cerebrum
(Figure 12.4):
 Frontal lobe
 Parietal lobe
 Temporal lobe
 Occipital lobe
 Insula
Figure 12.4b Structure of the cerebrum.
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THE CEREBRUM
THE CEREBRUM
• Five lobes of cerebrum (continued):
 Frontal lobes – most anterior lobes
o
Posterior border – called central sulcus; sits just behind
precentral gyrus
o
Neurons in these lobes are responsible for planning and
executing movement and complex mental functions such as
behavior, conscience, and personality
Figure 12.4a Structure of the cerebrum.
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THE CEREBRUM
THE CEREBRUM
• Five lobes of cerebrum (continued):
• Five lobes of cerebrum (continued):
 Parietal lobes – just posterior to frontal lobes
o
Contains postcentral gyrus posterior to central sulcus
o
Neurons in these lobes are responsible for processing and
integrating sensory information and function in attention
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 Temporal lobes – form lateral surfaces of each cerebral
hemisphere
o
Separated from parietal and frontal lobes by lateral fissure
o
Neurons in these lobes are involved in hearing, language,
memory, and emotions
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THE CEREBRUM
THE CEREBRUM
• Five lobes of cerebrum (continued):
• Five lobes of cerebrum (continued):
 Occipital lobes make up posterior aspect of each
cerebral hemisphere
o
Separated from parietal lobe by parieto-occipital sulcus
o
Neurons in these lobes process all information related to vision
 Insulas – deep underneath lateral fissures; neurons in
these lobes are currently thought to be involved in
functions related to taste and viscera (internal organs)
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THE CEREBRUM
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THE CEREBRUM-GRAY MATTER
• Gray Matter: Cerebral Cortex – functionally most
complex part of cortex; covers underlying cerebral
hemispheres
 Most of cerebral cortex is neocortex (most recently
evolved region of brain); has a huge surface area
 Composed of 6 layers (of neurons and neuroglia) of
variable widths (Figure 12.5)
 All neurons in cortex are interneurons
Figure 12.4c Structure of the cerebrum.
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THE CEREBRUM-GRAY MATTER
• Gray Matter: Cerebral Cortex (continued):
 Functions of neocortex revolve around conscious
processes such as planning movement, interpreting
incoming sensory information, and complex higher
functions
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THE CEREBRUM-GRAY MATTER
• Gray Matter: Cerebral Cortex (continued):
 Neocortex is divided into three areas: primary motor
cortex, primary sensory cortices, and association
areas (continued):
o
 Neocortex is divided into three areas: primary motor
o
cortex, primary sensory cortices, and association
areas (next slide)
o
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Primary motor cortex – plans and executes movement
Primary sensory cortices – first regions to receive and process
sensory input
Association areas integrate different types of information:
•
Unimodal areas integrate one specific type of information
•
Multimodal areas integrate information from multiple different
sources and carry out many higher mental functions
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THE CEREBRUM-GRAY MATTER
THE CEREBRUM-GRAY MATTER
Motor areas – most are located in frontal lobe; contain
upper motor neurons which are interneurons that
connect to other neurons (not skeletal muscle)
• Primary motor cortex; involved in conscious
planning of movement; located in precentral gyrus of
frontal lobe
• Upper motor neurons of each cerebral hemisphere
Figure 12.5 Structure of the cerebral cortex (left hemisphere, lateral view).
control motor activity of opposite side of body via PNS
neurons called lower motor neurons; execute order to
move
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THE CEREBRUM-GRAY MATTER
• Movement requires input from many motor association
areas such as large premotor cortex located anterior to
primary motor cortex
• Motor association areas are unimodal areas involved
in planning, guidance, coordination, and execution of
movement
• Frontal eye fields – paired motor association areas;
one on each side of brain anterior to premotor cortex;
involved in back and forth eye movements as in reading
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THE CEREBRUM-GRAY MATTER
Sensory Cortices
• Two main somatosensory areas in cerebral cortex;
deal with somatic senses; information about
temperature, touch, vibration, pressure, stretch, and
joint position
 Primary somatosensory area (S1) – in postcentral
gyrus of parietal lobe
 Somatosensory association cortex (S2) – posterior to
S1
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THE CEREBRUM-GRAY MATTER
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THE CEREBRUM-GRAY MATTER
Sensory Cortices (continued):
Sensory Cortices (continued):
• Special senses – touch, vision, hearing, smell, and taste
• Special senses (continued):
each have a primary and a unimodal association area as
does sense of equilibrium (balance); found in all lobes
of cortex except frontal lobe
 Primary visual cortex – at posterior end of occipital
 Primary auditory cortex – in superior temporal lobe;
first to receive auditory information; input is transferred
to nearby auditory association cortex and other
multimodal association areas for further processing
lobe; first area to receive visual input; transferred to
visual association area which processes color, object
movement, and depth
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THE CEREBRUM-GRAY MATTER
THE CEREBRUM-GRAY MATTER
Sensory Cortices (continued):
Sensory Cortices (continued):
• Special senses (continued):
• Special senses (continued):
 Gustatory cortex – taste information processing;
scattered throughout both insula and parietal lobes
 Vestibular areas – deal with equilibrium and
 Olfactory cortex – processes sense of smell; in
evolutionarily older regions of brain; consists of several
areas in limbic and medial temporal lobes
positional sensations; located in parietal and temporal
lobes
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THE CEREBRUM-GRAY MATTER
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THE CEREBRUM-GRAY MATTER
Multimodal association areas – regions of cortex that
allow us to perform complex mental functions:
• Language – processed in two areas of cortex:
 Broca’s area – in anterolateral frontal lobe; premotor
area responsible for ability to produce speech sounds
 Wernicke’s area (integrative speech area) – in
temporal and parietal lobes; responsible for ability to
understand language
Figure 12.5 Structure of the cerebral cortex (left hemisphere, lateral view).
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THE CEREBRUM-GRAY MATTER
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THE CEREBRUM-GRAY MATTER
Multimodal association areas (continued):
Multimodal association areas (continued):
• Prefrontal cortex occupies most of frontal lobe;
• Parietal and temporal association areas – occupy
communicates with diencephalon, other regions of
cerebral gray matter, and association areas located in
other lobes; many functions including modulating
behavior, personality, learning, memory, and an
individual’s personality state
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most of their respective lobes; perform multiple
functions including integration of sensory information,
language, maintaining attention, recognition, and
spatial awareness
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THE CEREBRUM-GRAY MATTER
THE CEREBRUM-GRAY MATTER
• Basal nuclei, found deep within each cerebral
hemisphere; cluster of neuron cell bodies, involved in
movement; separated from diencephalon by a region of
white matter called internal capsule; includes (Figure
12.6):
 Caudate nuclei
 Putamen
 Globus pallidus
Table 12.1 Motor, Sensory, and Association Areas of the Cerebral Cortex.
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THE CEREBRUM-GRAY MATTER
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THE CEREBRUM-GRAY MATTER
• Basal nuclei (continued):
 Caudate nuclei – C-shaped rings of gray matter; lateral
to lateral ventricle of each hemisphere with anteriorly
oriented tail
 Putamen – posterior and inferior to caudate nucleus;
connected to caudate nucleus by small bridges of gray
matter; combination of putamen and caudate are
sometimes called corpus striatum
 Globus pallidus sits medial to putamen; contains more
myelinated fibers than other regions
Figure 12.6 Structure of the basal nuclei (anterolateral view).
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THE CEREBRUM-WHITE MATTER
•
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THE CEREBRUM-WHITE MATTER
Cerebral white matter can be classified as one of three
types (Figure 12.7):
 Commissural fibers – connect right and left hemispheres;
corpus callosum, largest of four groups in this category, lies
in middle of brain at base of longitudinal fissure
 Projection fibers – connect cerebral cortex of one hemisphere
with other areas of same hemisphere, other parts of brain, and
spinal cord; corona radiata are fibers that spread out in a
radiating pattern; condense around diencephalon to form two
V-shaped bands called internal capsules
 Association fibers – restricted to a single hemisphere;
connect gray matter of cortical gyri with one another
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Figure 12.7 Structure of cerebral white matter.
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THE CEREBRUM-LIMBIC SYSTEM
•
THE CEREBRUM-LIMBIC SYSTEM
Possible pathway for information transferred by conduction
of an action potential from one region of brain to another
(Figure 12.8):
1. Action potential originates in gray matter
2. Action potential is sent to another area of gray matter by
projection fibers
3. Second (new) action potential is generated by gray matter;
spreads to neighboring gray matter by association fibers
4. Lastly, a third action potential is generated; can be sent to
other cerebral hemisphere by commissural fibers
Figure 12.8 A possible pathway for conduction of an action potential in the brain.
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THE CEREBRUM-LIMBIC SYSTEM
• Limbic system – important functional brain system,
includes limbic lobe (region of medial cerebrum),
hippocampus, amygdala, and pathways; connect each
of these regions of gray matter with rest of brain
(Figure 12.9)
 Found only within mammalian brains
 Involved in memory, learning, emotion, and behavior
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THE CEREBRUM-LIMBIC SYSTEM
• Limbic system (continued):
 Limbic lobe and associated structures form a ring on
medial side of cerebral hemisphere; contain two main
gyri: cingulate gyrus and parahippocampal gyrus
 Hippocampus – in temporal lobe; connected to a
prominent C-shaped ring of white matter (fornix) which
is its main output tract; involved in memory and learning
 Amygdala – anterior to hippocampus; involved in
behavior and expression of emotion, especially fear
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THE CEREBRUM-LIMBIC SYSTEM
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THE DIENCEPHALON
Diencephalon – at physical center of brain; composed of
four components, each with its own nuclei that receive
specific input and send output to other brain regions
(Figure 12.10):
• Thalamus
• Hypothalamus
• Epithalamus
• Subthalamus
Figure 12.9 Structures of the limbic system (anterolateral view).
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THE DIENCEPHALON
THE DIENCEPHALON
• Thalamus – main entry route of sensory data into
cerebral cortex (Figure 12.10a, b)
 Consists of two egg-shaped regions of gray matter; make
up about 80% of diencephalon
 Third ventricle is found between these two regions
 Thalamic nuclei receive afferent fibers from many other
regions of nervous system excluding information about
the sense of smell
Figure 12.10a, b Structure of the diencephalon.
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THE DIENCEPHALON
THE DIENCEPHALON
• Thalamus (continued):
• Thalamus (continued):
 Regulates cortical activity by controlling which input
should continue to cerebral cortex
 Association nuclei
o
 Each half of thalamus has three main groups of nuclei
separated by thin layers of white matter
o
o
 Specific nuclei function as relay stations that receive
Receive input from variety of sources
Process information related to emotions, memory, and
integration of sensory information
Processed information is sent on to appropriate association
areas of cerebral cortex
input, integrate information, then send information to
specific motor or sensory areas in cerebral cortex
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THE DIENCEPHALON
THE DIENCEPHALON
• Thalamus (continued):
• Hypothalamus – collection of nuclei anterior and
inferior to larger thalamus
 Nonspecific nuclei
o
o
o
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Receive information from basal nuclei, cerebellum, and motor
cortex
Send information to a wide range of locations including
cerebral cortex and other brain regions
Involved in controlling arousal, consciousness, and level of
responsiveness and excitability of cerebral cortex
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 Neurons perform several vital functions critical to
survival; include regulation of autonomic nervous
system, sleep/wake cycle, thirst and hunger, and body
temperature
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THE DIENCEPHALON
THE DIENCEPHALON
• Hypothalamus (continued):
• Hypothalamus (continued):
 Inferior hypothalamus – anatomically and functionally
 Antidiuretic hormone and oxytocin, hypothalamic
linked to pituitary gland by an extension called
infundibulum; hypothalamic tissue makes up posterior
portion of this endocrine gland
hormones that do not affect pituitary gland, have their
effect on water balance and stimulation of uterine
contraction during childbirth, respectively
 Hypothalamus secretes a number of different releasing
 Input to hypothalamus arrives from many sources
and inhibiting hormones; affect function of pituitary
gland; in turn, pituitary gland secretes hormones that
affect activities of other endocrine glands throughout
body
including cortex and basal nuclei
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THE DIENCEPHALON
THE DIENCEPHALON
• Hypothalamus (continued):
• Epithalamus – superior to thalamus; most of its
posterosuperior bulk is an endocrine gland called
pineal gland; secretes melatonin; hormone involved in
sleep/wake cycle
 Mammillary bodies – connect hypothalamus with
limbic system; receive input from hippocampus;
involved in memory regulation and behavior
 Input from outside nervous system; endocrine system
• Subthalamus – inferior to thalamus; functionally
connected with basal nuclei; together, they control
movement
(among others) provides information from receptors that
detect changes in body temperature and receptors that
detect changes in osmotic concentration of blood
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THE DIENCEPHALON
CEREBELLUM
Cerebellum – makes up posterior and inferior portion of
brain; functionally connected with cerebral cortex, basal
nuclei, brainstem, and spinal cord; interactions between
these regions together coordinate movement (Figure
12.11)
•
Anatomically, divided into two cerebellar hemispheres
connected by structure called vermis (Figure 12.11a)
•
Ridges called folia cover exterior cerebellar surface;
separated by shallow sulci; increases surface area of region
Figure 12.10c Structure of the diencephalon.
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CEREBELLUM
CEREBELLUM
Cerebellum (continued):
•
Divided into three lobes: anterior, posterior, and
flocculonodular lobes (Figure 12.11b)
•
Cerebellar cortex – outer layer of gray matter
•
Cortex is extremely folded and branching white matter is
called arbor vitae because it resembles tree branches
Figure 12.11a Structure of the cerebellum.
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CEREBELLUM
CEREBELLUM
Cerebellum (continued):
•
Inner white matter contains clusters of gray matter (deep
cerebellar nuclei) scattered throughout
•
White matter converges into three large tracts called
cerebellar peduncles; only connection between cerebellum
and brainstem
Figure 12.11b Structure of the cerebellum.
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CEREBELLUM
THE BRAINSTEM
Brainstem – one of oldest components of brain; vital to
our immediate survival as its nuclei control many basic
homeostatic functions such as heart rate and breathing
rhythms (Figures 12.12–12.15)
•
Controls many reflexes (programmed, automatic responses
to stimuli); functions in movement, sensation, and
maintaining alertness
Figure 12.11c, d Structure of the cerebellum.
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THE BRAINSTEM
THE BRAINSTEM
Brainstem (continued):
•
Located inferior to diencephalon, anterior to cerebellum,
and superior to spinal cord, on midsagittal section of brain
(Figure 12.12)
•
Extends to level of foramen magnum; along with fourth
ventricle (deep within brainstem), continuous with spinal
cord and its central canal
Figure 12.12a Midsagittal section of the brain showing the brainstem.
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THE BRAINSTEM
THE BRAINSTEM
Brainstem (continued):
•
Three subdivisions; superior midbrain, middle pons, and
inferior medulla oblongata, where following structures
reside:
 Fibers of cerebellum and related nuclei travel through
portions of brainstem where they either synapse with nuclei
found there or progress on to other destinations in cerebral
cortex or spinal cord
Figure 12.12b Midsagittal section of the brain showing the brainstem.
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THE BRAINSTEM
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THE BRAINSTEM
Brainstem (continued):
 Nuclei of reticular formation – group of connected nuclei
scattered throughout brainstem, many functions including
regulation of respiration, blood pressure, sleep/wake cycle,
pain perception, and consciousness
 Tracts of white matter between spinal cord and brain –
nearly all pathways to and from brain and spinal cord travel
through brainstem
 Cranial nerve nuclei – many cranial nerves originate in
brainstem; their nuclei have many sensory, motor, and
autonomic responsibilities
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Figure 12.13 External anatomy of the brainstem.
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THE BRAINSTEM
THE BRAINSTEM
• Midbrain
• Midbrain (continued):
 Inferior to diencephalon; surrounds cerebral aqueduct
(connects third and fourth ventricles) (Figure 12.14b)
 Includes following structures:
o
 Also known as mesencephalon; shortest and most
superior brainstem region
o
Superior and inferior colliculi, protrude from posterior
surface of brainstem; two paired projections that form roof of
midbrain (tectum); involved in visual and auditory functions
respectively; project to thalamus
Descending tracts – white matter tracts that originate in
cerebrum and form anteriormost portion of midbrain; called
crus cerebri
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THE BRAINSTEM
THE BRAINSTEM
• Midbrain (continued):
• Midbrain (continued):
 Includes following structures (continued):
o
o
 Includes following structures (continued):
Substantia nigra – posterior to crus cerebri, is a darkly
pigmented region whose neurons work with basal nuclei to
control movement
Red nucleus – posterior to substantia nigra; communicates
with cerebellum, spinal cord, and other regions involved in
regulating movement; role in humans not yet understood
o
o
Many cranial nerve nuclei are found in midbrain
Midbrain tegmentum – region of midbrain between cerebral
aqueduct and substantia nigra; contains numerous nuclei, many
of which are components of reticular formation; both
ascending and descending white matter tracts are found in this
region as well
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THE BRAINSTEM
THE BRAINSTEM
• Pons – inferior to midbrain; has a prominent anterior
surface that contains descending motor tracts from crus
cerebri, some of which pass through pons en route to
spinal cord
 Other tracts enter cerebellum by way of middle
cerebellar peduncle
• Pons (continued):
 Pontine tegmentum – surrounded by middle cerebellar
peduncles
 Pontine nuclei have many roles including: regulation of
movement, breathing, reflexes, and complex functions
associated with sleep and arousal
 Reticular formation and cranial nerve nuclei are located
posterior to these tracts
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THE BRAINSTEM
THE BRAINSTEM
• Medulla oblongata – most inferior structure of
brainstem; continuous with spinal cord at foramen
magnum (Figure 12.14c)
 Pyramids – on anterior surface of medulla, contain
upper motor neuron fibers of corticospinal tract (also
called the pyramidal tract) as they travel from cerebral
cortex to spinal cord
• Medulla oblongata (continued):
 Right and left corticospinal fibers decussate (crossover)
within pyramids; motor fibers originating from right side
of cerebral cortex descend through left side of spinal
cord and vice versa
 Posterior columns – paired tracts of white matter found
on medulla’s posterior surface; carry sensory
information from spinal cord to nucleus gracilis and
nucleus cuneatus
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THE BRAINSTEM
© 2016 Pearson Education, Inc.
THE BRAINSTEM
• Medulla oblongata (continued):
 Posterior columns also decussate within medulla so
sensory information from right side of spinal cord is
processed by left side of cerebral cortex and vice versa
 Olive – lateral to each pyramid; protuberance that
contains inferior olivary nucleus; receives sensory
fibers from spinal cord and directs information to
cerebellum
 Several cranial nerve and reticular formation nuclei are
found in medulla
Figure 12.14 Internal anatomy of brainstem divisions.
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LOCKED-IN SYNDROME
•
•
•
Caused by damage to motor tracts of pons; cerebral cortex
is unable to communicate with spinal cord; no purposeful
movement is possible, but sensory pathways to brain remain
intact (as do other cortical functions)
Patients are therefore literally “locked in” their bodies; yet
fully aware of everything going on around them; some can
communicate using eye movements controlled by midbrain
Small number of patients recover some motor functions but
most do not; overall prognosis is poor; most succumb to
infections or other paralytic complications
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THE BRAINSTEM
• Reticular formation – collection of over 100 nuclei
found in central core of three brainstem subdivisions
making this one of most complex regions of brain
(Figure 12.15)
 Input is received from multiple sources including:
cerebral cortex, limbic system, and sensory stimuli
 Output is sent throughout entire brain and spinal cord
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THE BRAINSTEM
THE BRAINSTEM
• Reticular formation (continued):
 Central nuclei (center of reticular formation) function in
sleep, pain transmission, and mood
 Nuclei surrounding central nuclei serve motor functions
for both skeletal muscles and autonomic nervous system
 Other nuclei are instrumental in homeostasis of
breathing and blood pressure
 Lateral nuclei play a role in sensation and in alertness
and activity levels of cerebral cortex
Figure 12.15 The reticular formation.
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THE BIG PICTURE OF MAJOR BRAIN
STRUCTURES AND THEIR FUNCTIONS
Figure 12.16 The Big Picture of Major Brain Structures and Their Functions.
© 2016 Pearson Education, Inc.
© 2016 Pearson Education, Inc.
THE BIG PICTURE OF MAJOR BRAIN
STRUCTURES AND THEIR FUNCTIONS
Figure 12.17 The Big Picture of Major Brain Structures and Their Functions.
© 2016 Pearson Education, Inc.
THE BIG PICTURE OF MAJOR BRAIN
STRUCTURES AND THEIR FUNCTIONS
MODULE 12.3 PROTECTION OF THE
BRAIN
Figure 12.17 The Big Picture of Major Brain Structures and Their Functions.
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BRAIN PROTECTION
BRAIN PROTECTION
Three features within protective shell of skull provide
additional shelter for delicate brain tissue:
• Cranial meninges – three layers of membranes that
• Cranial meninges – composed of three protective
membrane layers of mostly dense irregular
collagenous tissue
 Structural arrangement from superficial to deep:
surround brain
• Cerebrospinal fluid (CSF) – fluid that bathes brain
epidural space, dura mater, subdural space, arachnoid
mater, subarachnoid space, and pia mater (Figure 12.18)
and fills cavities
• Blood-brain barrier – prevents many substances from
entering brain and its cells from blood
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© 2016 Pearson Education, Inc.
BRAIN PROTECTION
BRAIN PROTECTION
• Cranial meninges (continued):
• Cranial meninges (continued):
 Epidural space – between inner surface of cranial bones
and outer surface of dura mater; only a potential space
as dura is normally tightly bound to bone only allowing
for passage of blood vessels
 Dura mater (dura) (continued):
o
 Dura mater (dura) – outermost meninx; thickest and
most durable of three meningeal layers; double-layered
membrane composed mostly of collagen fibers with few
elastic fibers
Two layers of dura (Figure 12.18a):
•
Periosteal dura – outer layer; attached to inner surface of bones
of cranial cavity; functions as periosteum with extensive blood
supply in epidural space
•
Meningeal dura – inner layer; avascular and lies superficial to
arachnoid mater
•
Mostly fused, creating a single inelastic membrane except in
regions where cavities called dural sinuses are found
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© 2016 Pearson Education, Inc.
BRAIN PROTECTION
BRAIN PROTECTION
• Cranial meninges (continued):
• Cranial meninges (continued):
 Dura mater (dura) (continued):
o
 Dura mater (dura) (continued):
Dural sinuses – venous channels; drain CSF and deoxygenated
blood from brain’s extensive network of veins; also found
where meningeal dura folds over itself and courses between
structures in brain
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o
Dural folds include falx cerebri, tentorium cerebelli, and falx
cerebelli (Figure 12.14b)
•
Falx cerebri – within longitudinal fissure; forms partition
between left and right cerebral hemispheres; superior sagittal
sinus (large dural sinus) found superior to falx cerebri
•
Tentorium cerebelli – partition between cerebellum and
occipital lobe of cerebrum
•
Falx cerebelli – partition between left and right hemispheres of
cerebellum
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BRAIN PROTECTION
BRAIN PROTECTION
• Cranial meninges (continued):
• Cranial meninges (continued):
 Subdural space – serous fluid-filled space; found deep
to dura mater and superficial to arachnoid mater; houses
veins that drain blood from brain
 Arachnoid mater – second meningeal layer deep to
 Arachnoid mater (continued):
o
Arachnoid trabeculae – composed of collagen fiber bundles
and fibroblasts; anchor arachnoid to deep pia mater
o
Arachnoid granulations (villi) – small bundles of arachnoid;
project superficially through meningeal dura into the dural
sinuses; allow for return of CSF to bloodstream
subdural space; thin weblike membrane composed of
dense irregular collagenous tissue with some degree of
elasticity (Figure 12.18c)
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© 2016 Pearson Education, Inc.
BRAIN PROTECTION
BRAIN PROTECTION
• Cranial meninges (continued):
• Cranial meninges (continued):
 Subarachnoid space – found deep to arachnoid mater
and superficial to pia mater; contains major blood
vessels of brain; filled with CSF
 Pia mater – deepest meningeal layer; only meninx in
physical contact with brain tissue
 Pia mater (continued):
o
Follows contour of brain, covering delicate tissue of every
sulcus and fissure
o
Permeable to substances in brain extracellular fluid and CSF;
allows for substances to move between these two fluid
compartments; helps to balance concentration of different
solutes found in each fluid
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BRAIN PROTECTION
© 2016 Pearson Education, Inc.
BRAIN PROTECTION
Figure 12.18a, b Structure of the cranial meninges and dural sinuses.
Figure 12.18c Structure of the cranial meninges and dural sinuses.
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© 2016 Pearson Education, Inc.
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THE VENTRICLES AND
CEREBROSPINAL FLUID
• Four ventricles within brain are linked cavities that are
continuous with central canal of spinal cord (Figures
12.19, 12.20)
THE VENTRICLES AND
CEREBROSPINAL FLUID
• Right and left lateral ventricles (first and second
ventricles); within their respective cerebral hemisphere
(Figure 12.19):
 Resemble ram’s horns when observed in anterior view;
 Lined with ependymal cells
horseshoe-shaped appearance in lateral view
 Filled with cerebrospinal fluid
 Three regions: anterior horn, inferior horn, and
posterior horn
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THE VENTRICLES AND
CEREBROSPINAL FLUID
© 2016 Pearson Education, Inc.
THE VENTRICLES AND
CEREBROSPINAL FLUID
• Third ventricle – narrow cavity found between two
lobes of diencephalon; connected to lateral ventricles
by interventricular foramen
• Fourth ventricle – between pons and cerebellum;
connected to third ventricle by cerebral aqueduct
(small passageway through midbrain)
 Continuous with central canal of spinal cord
 Contains several posterior openings that allow CSF in
ventricles to flow into subarachnoid space (Figure
12.19a)
© 2016 Pearson Education, Inc.
THE VENTRICLES AND
CEREBROSPINAL FLUID
• Cerebrospinal fluid (CSF) – clear, colorless liquid
similar in composition to blood plasma; protects brain
in following ways:
 Cushions brain and maintains a constant temperature
Figure 12.19 Ventricles of the brain.
© 2016 Pearson Education, Inc.
THE VENTRICLES AND
CEREBROSPINAL FLUID
• Choroid plexuses – where majority of CSF is
manufactured; found in each of four ventricles where
blood vessels come into direct contact with ependymal
cells (also produce some CSF themselves)
 Fenestrated capillaries have gaps between endothelial
within cranial cavity
 Removes wastes and increases buoyancy of brain; keeps
brain from collapsing under its own weight
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cells; allow fluids and electrolytes to exit from blood
plasma to enter extracellular fluid (ECF)
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THE VENTRICLES AND
CEREBROSPINAL FLUID
THE VENTRICLES AND
CEREBROSPINAL FLUID
•
• Choroid plexuses (continued):
 About 150 ml (2/3 cup) of CSF circulates through brain
Pathway for formation, circulation, and reabsorption of
CSF (Figure 12.20):
 Fluid and electrolytes leak out of capillaries of choroid
and spinal cord
plexuses into ECF of ventricles
 750–800 ml of CSF is produced daily so old CSF must
 Taken up into ependymal cells; then secreted into ventricles
be removed as choroid plexuses make new CSF
as CSF
 Process of CSF production and removal occurs
 Circulated through and around brain and spinal cord in
constantly; CSF is completely replaced every 5–6 hours
subarachnoid space; assisted by movement of ependymal cell
cilia
 Some CSF is reabsorbed into venous blood in dural sinuses
via arachnoid granulations
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© 2016 Pearson Education, Inc.
THE VENTRICLES AND
CEREBROSPINAL FLUID
THE BLOOD-BRAIN BARRIER
Blood-brain barrier – protective safeguard that separates
CSF and brain ECF from chemicals and disease-causing
organisms sometimes found in blood plasma (Figure
12.21)
•
Consists mainly of simple squamous epithelial cells
(endothelial cells) of blood capillaries, their basal laminae,
and astrocytes
Figure 12.20 Formation and flow of cerebrospinal fluid (CSF).
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© 2016 Pearson Education, Inc.
THE BLOOD-BRAIN BARRIER
THE BLOOD-BRAIN BARRIER
• Unique features of endothelial cells found in barrier:
• Substances that easily pass through plasma membranes
 Neighboring endothelial cells are bound together by
many tight junctions; prevent fluids and molecules
from passing between them; influenced by activity of
astrocytes on developing brain
 Limited capacity for movement of molecules and
substances into and out of cell by endocytosis and
exocytosis
© 2016 Pearson Education, Inc.
are able to pass through blood-brain barrier; include
water, oxygen, carbon dioxide, and nonpolar, lipidbased molecules
• Protein channels or carriers allow for passage of other
essential molecules across blood-brain barrier; include
glucose, amino acids, and ions
• Most large, polar molecules are effectively prevented
from crossing blood-brain barrier in any significant
amount; while barrier is protective, it can hinder access
of medications into brain
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THE BLOOD-BRAIN BARRIER
CONCEPT BOOST: WHERE EXACTLY
IS BLOOD-BRAIN BARRIER?
• No single structure is labeled “blood-brain barrier” on
any figure because blood-brain barrier isn’t around
brain; it’s within brain
• Not located in one distinct place but found throughout
entire brain
• To understand this, we must first understand body’s
tiniest blood vessels; capillaries are vessels that deliver
oxygen and nutrients to body’s cells and remove any
wastes produced by cells
Figure 12.21 The blood-brain barrier.
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© 2016 Pearson Education, Inc.
CONCEPT BOOST: WHERE EXACTLY
IS BLOOD-BRAIN BARRIER?
• Capillaries found in most organs and tissues are fairly
INFECTIOUS MENINGITIS
•
Potentially life-threatening infection of meninges in
subarachnoid space; inflammation occurs, causing classic
signs: headache, lethargy, stiff neck, fever
•
Diagnosis – examination of CSF for infectious agents and
white blood cells (cells of immune system); bacteria and
viruses are most common causative agents:
leaky; allow a wide variety of substances to move from
blood to extracellular fluid (and vice versa)
• Capillaries of brain are specialized to allow only
selected substances to enter its extracellular fluid;
effectively act as a “barrier”; prevents other substances
from doing so (Figure 12.21)
• Blood-brain barrier, therefore, is actually a property of
capillaries found throughout brain rather than a distinct
physical barrier
 Viral – generally mild; resolves in 1–2 weeks
 Bacterial – can rapidly progress to brain involvement and
death; aggressive antibiotic treatment necessary; some most
common forms are preventable with vaccines
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© 2016 Pearson Education, Inc.
THE SPINAL CORD
• Spinal cord – composed primarily of nervous tissue;
MODULE 12.4 THE SPINAL CORD
responsible for both relaying and processing
information; less anatomically complex than brain but
still vitally important to normal nervous system
function; two primary roles:
 Serves as a relay station and as an intermediate point
between body and brain; only means by which brain can
interact with body below head and neck
 Processing station for some less complex activities such
as spinal reflexes; do not require higher level processing
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PROTECTION OF THE SPINAL
CORD
Brain’s meninges pass through foramen magnum to
provide a continuous protective covering of spinal cord
and distal nerves at base (Figure 12.22)
•
Three spinal meninges include dura mater, arachnoid, and
pia mater; structurally similar to brain meninges except
that spinal cord dura has only one layer and pia mater has
some structural enhancements (Figure 12.22a)
PROTECTION OF THE SPINAL
CORD
•
Three spinal meninges include dura mater, arachnoid, and
pia mater; structurally similar to brain meninges except
that spinal cord dura has only one layer and pia mater has
some structural enhancements (Figure 12.22a) (continued):
 Spinal dura mater does not have periosteal layer found in
dura mater of brain; consists of only a meningeal layer
 Spinal pia mater has added function of anchoring spinal cord
to surrounding vertebral cavity; thin pia extensions called
denticulate ligaments pass through arachnoid and adhere to
dura mater
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PROTECTION OF THE SPINAL
CORD
• Actual or potential spaces between spinal cord
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PROTECTION OF THE SPINAL
CORD
• Actual or potential spaces between spinal cord
meninges are same as those found between cranial
meninges with following features (Figure 12.22b):
meninges are same as those found between cranial
meninges with following features (Figure 12.22b):
 Epidural space – actual space due to absence of a
 Subdural space – only a potential space much like
periosteal dura; found between meningeal dura and walls
of vertebral foramina; space is filled with veins and
adipose tissue; cushions and protects spinal cord
epidural space surrounding brain; dura and arachnoid are
normally adhered to one another
 Subarachnoid space – found between arachnoid and
pia mater; filled with CSF; base of spinal cord contains a
large volume of CSF; useful site for withdrawing
samples for clinical laboratory testing
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PROTECTION OF THE SPINAL
CORD
Figure 12.22a Structure of the spinal meninges.
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PROTECTION OF THE SPINAL
CORD
Figure 12.22b Structure of the spinal meninges.
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EPIDURAL ANESTHESIA AND
LUMBAR PUNCTURES
• Epidural (spinal) anesthesia – local anesthetic
medication is injected into epidural space through an
inserted needle
• Causes “numbing” (inability to transmit motor or
sensory impulses) of nerves extending off spinal cord
below level of injection
• Commonly given during childbirth and other surgical
procedures
EPIDURAL ANESTHESIA AND
LUMBAR PUNCTURES
• Lumbar puncture (spinal tap) – needle inserted into
subarachnoid space between fourth and fifth lumbar
vertebrae; avoids possibility of injuring spinal cord
• CSF is withdrawn for
analysis; used to assess
conditions like
meningitis, encephalitis
and multiple sclerosis
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EXTERNAL SPINAL CORD
ANATOMY
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EXTERNAL SPINAL CORD
ANATOMY
Spinal cord extends proximally from foramen magnum to
region between first and second lumbar vertebrae;
following structural features can be seen on spinal cord
(Figure 12.23):
• Filum terminale – found between first and second
•
Narrow posterior median sulcus can be seen on entire
length of posterior side of cord
• Spinal cord has two enlarged regions (cervical and
•
Wider anterior median sulcus can be seen on entire length
of anterior side of cord
•
Conus medullaris is cone-shaped distal end of cord
lumbar vertebrae; composed of spinal pia mater; thin
layer of pia continues through vertebral cavity to form
an anchor that is attached to first coccygeal vertebra
lumbar enlargements); nerve roots fuse together to
form spinal nerves (serve upper and lower extremities
respectively) in these enlargements (Figure 12.23a)
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EXTERNAL SPINAL CORD
ANATOMY
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EXTERNAL SPINAL CORD
ANATOMY
• Spinal nerves are components of PNS; carry sensory
and motor impulses to and from spinal cord
 Projections visible on each side of spinal cord between
vertebrae are called posterior and anterior nerve roots
 Roots of spinal nerves extend inferiorly from conus
medullaris and fill remainder of vertebral cavity; this
bundle of spinal nerve roots is called cauda equina due
to its horsetail-like appearance
Figure 12.23 External structure of the spinal cord.
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INTERNAL SPINAL CORD
ANATOMY
INTERNAL SPINAL CORD
ANATOMY
Butterfly-shaped spinal gray matter is surrounded by
tracts of white matter; following features are seen on
cross section of spinal cord (Figures 12.24, 12.25):
• Anterior to posterior orientation of spinal cord can be
•
• Anterior wings are broader while thinner posterior
Central canal – filled with CSF; seen in center of spinal
cord; surrounded by two thin strips of gray matter (gray
commissure); connects each “butterfly” wing
determined by using shape and size of gray matter
wings
wings extend almost to outer surface of spinal cord
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INTERNAL SPINAL CORD
ANATOMY
• Spinal gray matter makes up three distinct regions
found within spinal cord; houses neurons with specific
functions and includes (Figure 12.24):
 Anterior horn (ventral horn) makes up anterior wing
of gray matter and gives rise to anterior motor nerve
roots; neuron cell bodies found in this region are
involved in somatic motor functions (skeletal muscle
contraction)
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INTERNAL SPINAL CORD
ANATOMY
• Spinal gray matter (continued):
 Posterior horn (or dorsal horn) makes up posterior
wing of gray matter and gives rise to posterior sensory
nerve roots; neuron cell bodies found in this region are
involved in processing incoming somatic and visceral
sensory information
 Lateral horn, found only in spinal cord between first
thoracic vertebra and lumbar region; contains cell
bodies of neurons involved in control of viscera via
autonomic nervous system
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INTERNAL SPINAL CORD
ANATOMY
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INTERNAL SPINAL CORD
ANATOMY
• Spinal White Matter: Ascending and Descending
Tracts
 Contains axons of neurons that travel to and from brain;
allows spinal cord to fulfill one of its primary functions
as a relay station
 Organized into general regions called funiculi; three
(posterior funiculus, lateral funiculus, and anterior
funiculus) lie on each side of spinal cord (Figure 12.25)
Figure 12.24 Overview of internal spinal cord structure and function.
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INTERNAL SPINAL CORD
ANATOMY
• Spinal White Matter (continued):
• Spinal White Matter (continued):
 Funiculi features
o
INTERNAL SPINAL CORD
ANATOMY
 Ascending tracts carry various kinds of sensory
White matter in each funiculus is organized into tracts or
columns; bilaterally symmetrical (left and right side of spinal
cord have identical tracts serving their respective side of body)
o
Ascending and descending tracts bring information to and from
a specific part of brain
o
Sensory pathways travel in posterior and lateral funiculi
while motor pathways travel in anterior and lateral funiculi
information (Figure 12.25a):
o
Posterior columns – found in posterior funiculus; made up of
two tracts, medial fasciculus gracilis and lateral fasciculus
cuneatus; carry somatosensory information, such as
proprioception and touch; nucleus gracilis transmits stimuli
from lower limbs and lower trunk while nucleus cuneatus
transmits stimuli from upper limbs and upper trunk
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INTERNAL SPINAL CORD
ANATOMY
© 2016 Pearson Education, Inc.
INTERNAL SPINAL CORD
ANATOMY
• Spinal White Matter (continued):
 Ascending tracts (continued):
o
o
Spinocerebellar tracts – found in lateral funiculi; carry
information about joint position and muscle stretch from entire
body to cerebellum
Anterolateral system includes spinothalamic tracts that travel
in anterior and lateral funiculi; transmit pain and temperature
stimuli from entire body to brain
Figure 12.25a Ascending and descending tracts of the spinal cord.
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INTERNAL SPINAL CORD
ANATOMY
© 2016 Pearson Education, Inc.
INTERNAL SPINAL CORD
ANATOMY
• Spinal White Matter (continued):
 Descending tracts transmit motor information from
specific regions in brain down spinal cord to specific
regions in body (Figure 12.25b)
o
Corticospinal tracts – largest of descending tracts; help
control skeletal muscles below head and neck
o
Originate from motor areas of cerebral cortex; descend as part
of internal capsule then decussate within brainstem
Travel through lateral funiculi of spinal cord; fibers deliver
motor information to appropriate locations in anterior horn
o
Figure 12.25b Ascending and descending tracts of the spinal cord.
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SENSORY STIMULI
• Sensory stimuli – those effects that cause senses to
respond; multiple sensory stimuli from different
regions of brain can be pulled together into a single
mental picture
MODULE 12.5 SENSATION PART I:
ROLE OF THE CNS IN SENSATION
 Each of these disparate stimuli reaches brain in
following two-part process:
o
Stimulus is detected by neurons in PNS and sent as sensory
input to CNS
o
In CNS, sensory input is sent to cerebral cortex for
interpretation
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SENSORY STIMULI
GENERAL SOMATIC SENSES
• Sensory stimuli (continued):
 When CNS has received all different sensory inputs, it
integrates them into a single perception (a conscious
awareness of sensation)
 Sensations can be grouped into two basic types:
o
o
Special senses – detected by special sense organs and include
vision, hearing, equilibrium, smell, and taste
General senses – detected by sensory neurons in skin, muscles,
or walls of organs; can be further subdivided into general
somatic senses that involve skin, muscles, and joints and
general visceral senses that involve internal organs
General somatic senses pertain to touch, stretch, joint
position, pain, and temperature (Figures 12.26–12.28)
•
Two types of touch stimuli are delivered to appropriate part
of cerebral cortex by different pathways:
 Tactile senses – (fine or discrimination touch) include
vibration, two-point discrimination, and light touch
 Nondiscriminative touch (crude touch) lacks fine spatial
resolution of tactile senses
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GENERAL SOMATIC SENSES
• Most of general somatic senses are considered
mechanical senses; neurons that detect them are
responsive to mechanical deformation
• Two major ascending tracts in spinal cord carry
somatic sensory information to brain: posterior
columns/medial lemniscal system and anterolateral
system
© 2016 Pearson Education, Inc.
GENERAL SOMATIC SENSES
• Basic pathway consists of following:
 First-order neuron detects initial stimulus in PNS;
axon of this neuron then synapses on a second-order
neuron
 Second-order neuron – interneuron located in posterior
horn of spinal cord or in brainstem; relays stimulus to a
third-order neuron
 Third-order neuron – an interneuron found in
thalamus; delivers impulse to cerebral cortex
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GENERAL SOMATIC SENSES
GENERAL SOMATIC SENSES
• Posterior columns/medial lemniscal system includes
axons of neurons that transmit tactile information about
discriminative touch and axons that convey information
regarding proprioception (Figure 12.26)
 Ascend through posterior columns; medial fasciculus
gracilis (carries impulses from lower limbs) and
fasciculus cuneatus (carries impulses from upper limbs,
trunk, and neck)
© 2016 Pearson Education, Inc.
GENERAL SOMATIC SENSES
© 2016 Pearson Education, Inc.
GENERAL SOMATIC SENSES
• Posterior columns/medial lemniscal system
(continued):
 Fasciculus gracilis and cuneatus axons synapse with
second-order neurons when they enter medulla, nucleus
gracilis, and nucleus cuneatus, respectively
 Axons of second-order neurons decussate and form
tracts called medial lemniscus
 Fibers of medial lemniscus ascend through pons and
midbrain until they reach third-order neurons in
thalamus; axons of these third-order neurons proceed to
cerebral cortex
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GENERAL SOMATIC SENSES
Figure 12.26 Ascending (sensory) pathways: the posterior column/medial lemniscal
systems in the right and left sides of the body.
© 2016 Pearson Education, Inc.
GENERAL SOMATIC SENSES
• Anterolateral system fibers transmit pain,
temperature, and nondiscriminative touch stimuli in
anterolateral spinal cord (Figure 12.27)
 First-order neurons synapse on second-order neurons in
posterior horn; then decussate
 Spinothalamic tract – largest member of anterolateral
system; transmits signals through spinal cord to sensory
relay nuclei of thalamus; third-order neurons in thalamus
then transmit impulses to cerebral cortex
Figure 12.27 Ascending (sensory) pathways: the right and left spinothalamic tracts (part of
the anterolateral system).
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GENERAL SOMATIC SENSES
• Role of Cerebral Cortex in Sensation, S1 and
Somatotopy:
GENERAL SOMATIC SENSES
• Role of Cerebral Cortex (continued):
 Mapping of primary somatosensory cortex (S1)
 Thalamus relays most incoming information to primary
somatosensory cortex (S1) in postcentral gyrus
illustrates that different parts of body are unequally
represented (Figure 12.28a)
 Each part of body is represented by a specific region of
 More S1 space is dedicated to hands and face; represents
S1, a type of organization called somatotopy (Figure
12.28)
importance of manual dexterity, facial expression, and
speech to human existence
 Unequal representation of body parts in S1 is
exemplified by sensory homunculus (Figure 12.28b)
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GENERAL SOMATIC SENSES
© 2016 Pearson Education, Inc.
GENERAL SOMATIC SENSES
• Role of the Cerebral Cortex in Sensation –
Processing of Touch Stimuli:
 Thalamic nuclei relay touch information from
spinothalamic tracts and posterior columns primarily to
S1 for conscious perception
 Once sensory information reaches S1, it is processed,
perceived, and passed along to cortical association areas
Figure 12.28 Representations of the primary somatosensory cortex.
© 2016 Pearson Education, Inc.
GENERAL SOMATIC SENSES
• Role of the Cerebral Cortex in Sensation –
Processing of Touch Stimuli (continued):
 Somatosensory association cortex (S2) plays a major
role in processing sensory input and sending it to limbic
system
 Limbic system is involved in tactile learning and
memory
 S1 also sends sensory input to parietal and temporal
association areas which integrate and relay information
to motor areas of frontal lobe
© 2016 Pearson Education, Inc.
© 2016 Pearson Education, Inc.
GENERAL SOMATIC SENSES
• Role of the Cerebral Cortex in Sensation –
Processing of Pain Stimuli: perception of pain stimuli
is called nociception
 Thalamus relays pain stimuli to several brain regions
including S1 and S2 where sensory discrimination
(localization, intensity, and quality) is perceived and
analyzed
 Also sent to basal nuclei, regions of limbic system,
hypothalamus, and prefrontal cortex, where emotional
and behavioral aspects of pain are processed
© 2016 Pearson Education, Inc.
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GENERAL SOMATIC SENSES
• Role of the Cerebral Cortex in Sensation –
Processing of Pain Stimuli (continued):
GENERAL SOMATIC SENSES
• Role of the Cerebral Cortex in Sensation –
Processing of Pain Stimuli (continued):
 Cerebral cortex appears to have a significant influence
on perception and modulation of pain; evident by a
phenomenon called placebo effect where a dummy
treatment with no active pain-killing ingredients
produces pain relief
 A descending pathway originating mostly in S1,
amygdala, and a region of midbrain called
periaqueductal gray matter provides an explanation
for placebo effect
 Neurons in the periaqueductal gray matter release
neurotransmitters called endorphins
© 2016 Pearson Education, Inc.
© 2016 Pearson Education, Inc.
GENERAL SOMATIC SENSES
• Role of the Cerebral Cortex in Sensation –
Processing of Pain Stimuli (continued):
 Endorphins decrease sensitivity to pain stimuli of
posterior horn neurons
o
o
o
Pain input is still present and its intensity is unaffected
CNS neurons perceive pain as being less intense (or absent)
Example of Cell-Cell Communication Core Principle
PHANTOM LIMB PAIN
• Phantom limb – occurs after amputation of limb, digit,
or even breast; patients perceive body part is still
present and functional in absence of sensory input;
small percentage develop phantom pain (burning,
tingling, or severe pain) in missing part
• Difficult to treat due to complex way CNS processes
pain; supports idea that S1 has “map” of body that
exists independently of PNS
• Over time, map generally rearranges itself so body is
represented accurately; phantom sensations decrease
© 2016 Pearson Education, Inc.
© 2016 Pearson Education, Inc.
INTRODUCTION TO SPECIAL
SENSES
INTRODUCTION TO SPECIAL
SENSES
• Special senses include vision, hearing (audition), taste
• Special senses include vision, hearing (audition), taste
(gustation), smell (olfaction), and balance (vestibular
sensation)
(gustation), smell (olfaction), and balance (vestibular
sensation) (continued):
 Each involves neurons that detect a stimulus and send it
to CNS for processing and integration
 Pathways for processing each type of special sensory
stimuli:
 Thalamus – gateway for entry of special sensory stimuli
into cerebral cortex; interprets majority of this
information; olfaction is exception
© 2016 Pearson Education, Inc.
o
Visual
•
Most stimuli are sent directly to thalamus; then relayed to
primary visual cortex (processes stimuli and perceives an object’s
depth, color, and detects rapid changes in stimuli)
•
Information is shared with association areas in temporal and
parietal lobes; crucial for object recognition and spatial
awareness, respectively
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INTRODUCTION TO SPECIAL
SENSES
INTRODUCTION TO SPECIAL
SENSES
• Special senses include vision, hearing (audition), taste
• Special senses include vision, hearing (audition), taste
(gustation), smell (olfaction), and balance (vestibular
sensation) (continued):
(gustation), smell (olfaction), and balance (vestibular
sensation) (continued):
 Pathways for processing each type of special sensory
stimuli (continued):
o
 Pathways for processing each type of special sensory
stimuli (continued):
Auditory
o
Gustatory
•
Stimuli first go to nuclei in brainstem where limited processing
occurs
•
Stimuli are sent to nuclei in medulla before being relayed to
thalamus
•
Majority of stimuli are routed to thalamus and then primary
auditory cortex (superior temporal lobe), for sound processing
•
Then sent to gustatory cortices (insula and parietal lobes) for
processing
•
Information is relayed to other association areas such as
Wernicke’s area for language comprehension
•
Information is sent to hypothalamus and limbic system likely for
processing of taste preferences and food-seeking behaviors
© 2016 Pearson Education, Inc.
© 2016 Pearson Education, Inc.
INTRODUCTION TO SPECIAL
SENSES
INTRODUCTION TO SPECIAL
SENSES
• Special senses include vision, hearing (audition), taste
• Special senses include vision, hearing (audition), taste
(gustation), smell (olfaction), and balance (vestibular
sensation) (continued):
(gustation), smell (olfaction), and balance (vestibular
sensation) (continued):
 Pathways for processing each type of special sensory
stimuli (continued):
o
 Pathways for processing each type of special sensory
stimuli (continued):
Olfactory
o
•
Stimuli enter limbic system of cerebral cortex for initial
processing, bypassing thalamus
•
Then sent to several regions of brain including thalamus, prefrontal
cortex, hypothalamus, and other limbic system components
•
Allows smell stimuli to influence behaviors such as emotion,
cognition, and those related to feeding
Balance
•
Processing vestibular stimuli involves several brainstem nuclei,
cerebellum, descending pathways through spinal cord, and
pathways through thalamus to cerebral cortex
© 2016 Pearson Education, Inc.
© 2016 Pearson Education, Inc.
VOLUNTARY MOVEMENT
• Planning and coordination of voluntary movement are
MODULE 12.6 MOVEMENT PART I:
ROLE OF THE CNS IN VOLUNTARY
MOVEMENT
© 2016 Pearson Education, Inc.
carried out within CNS; involve motor areas of cerebral
cortex, basal nuclei, cerebellum, and spinal cord
• Three types of neurons are directly involved in eliciting
a muscle contraction (next slide)
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VOLUNTARY MOVEMENT
1.
Upper motor neurons with cell bodies in motor area
of cerebral cortex (most) or brainstem (some) – axons
descend through cerebral white matter to brainstem
and spinal cord; synapse with local interneurons
2.
Local interneurons – pass messages from upper motor
neurons to neighboring lower motor neurons
3.
Cell bodies of lower motor neurons reside in anterior
horn of spinal gray matter; axons (components of
PNS) exit CNS to innervate skeletal muscles
MOTOR PATHWAYS FROM BRAIN
THROUGH SPINAL CORD
• Axons from cortical motor areas unite to form several
white matter tracts; largest of these tracts are (Figure
12.29):
 Corticospinal tract – controls muscles below head and
neck utilizing lower motor neurons of spinal nerves
 Corticonuclear tract – formerly known as
corticobulbar tracts; controls muscles of head and neck
utilizing lower motor neurons of cranial nerves
© 2016 Pearson Education, Inc.
MOTOR PATHWAYS FROM BRAIN
THROUGH SPINAL CORD
• Corticospinal tract pathway (Figure 12.29):
 Axons that form corticospinal tracts originate from
upper motor neuron cell bodies in primary motor and
premotor cortices
© 2016 Pearson Education, Inc.
MOTOR PATHWAYS FROM BRAIN
THROUGH SPINAL CORD
• Corticospinal tract pathway (continued):
 Most of these fibers decussate at level of medullary
pyramids; neurons on right side of brain send fibers to
left side of body and vice versa
 Axons unite and descend through corona radiata and
 Fibers that decussate travel in lateral funiculi; are then
internal capsule on way to brainstem (midbrain and
pons)
known as right and left lateral corticospinal tracts
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MOTOR PATHWAYS FROM BRAIN
THROUGH SPINAL CORD
© 2016 Pearson Education, Inc.
MOTOR PATHWAYS FROM BRAIN
THROUGH SPINAL CORD
• Corticospinal tract pathway (continued):
 Fibers of lateral corticospinal tracts synapse on local
interneurons in anterior horn of spinal gray matter; over
half terminate in cervical spinal cord to control motor
functions of upper limbs
 10–15% of motor fibers from cerebrum do not
decussate; travel through anterior funiculi of spinal
white matter; become right and left anterior
corticospinal tracts
Figure 12.29 Descending (motor) pathways: the right and left lateral corticospinal tracts.
© 2016 Pearson Education, Inc.
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MOTOR PATHWAYS FROM BRAIN
THROUGH SPINAL CORD
• Corticonuclear tracts originate from cell bodies of
upper motor neurons; travel with corticospinal tracts
through corona radiata and internal capsule to
brainstem
MOTOR PATHWAYS FROM BRAIN
THROUGH SPINAL CORD
• Corticonuclear tracts (continued):
 Cranial nerve nuclei give rise to lower motor neurons
that innervate muscles of head and neck
 Fibers do not decussate but most cranial nerve nuclei
 Do not enter spinal cord; instead synapse on
interneurons that communicate with cranial nerve nuclei
at various levels of brainstem
communicate with upper motor neurons from both
cerebral hemispheres; damage to upper motor neurons
on one side of cerebrum does not lead to noticeable
deficits from many cranial nerves
© 2016 Pearson Education, Inc.
ROLE OF BRAIN IN VOLUNTARY
MOVEMENT
Even simple movements require simultaneous firing of
countless neurons as part of a selected group of actions
called a motor program
•
•
Execution of any motor program requires firing of neurons
in motor association areas, firing of upper motor neurons,
and input from basal nuclei, cerebellum, spinal cord, and
multimodal association areas (prefrontal cortex and various
sensory areas)
© 2016 Pearson Education, Inc.
ROLE OF BRAIN IN VOLUNTARY
MOVEMENT
• Role of Cerebral Cortex – majority of upper motor
neurons that control complex movements reside in
primary motor cortex and premotor and motor
association areas
 Plan and initiate voluntary movement by selecting an
appropriate motor program and coordinating sequence
of skilled movements
Firing of lower motor neurons in PNS is necessary to
complete task
© 2016 Pearson Education, Inc.
ROLE OF BRAIN IN VOLUNTARY
MOVEMENT
• Role of Cerebral Cortex (continued):
© 2016 Pearson Education, Inc.
ROLE OF BRAIN IN VOLUNTARY
MOVEMENT
• Role of Cerebral Cortex (continued):
 Upper motor neurons are also located in certain nuclei of
brainstem; work to maintain posture, balance, and body
position especially during locomotion; also produce
motor responses to sensory stimuli
 Map of upper motor neurons in primary motor cortex
and motor homunculus resemble sensory map and
homunculus (Figure 12.30)
© 2016 Pearson Education, Inc.
 Primary motor cortex is organized somatotopically;
certain body regions have disproportionately more
cortical area devoted to them (especially lips, tongue,
and hands); signifies importance of vocalization and
manual dexterity to human survival
 Upper motor neurons do not act alone when delivering
commands to lower motor neurons; smooth, fluid
motion requires input from basal nuclei and cerebellum
© 2016 Pearson Education, Inc.
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ROLE OF BRAIN IN VOLUNTARY
MOVEMENT
ROLE OF BRAIN IN VOLUNTARY
MOVEMENT
• Role of Basal Nuclei – three collections of cell bodies
make up basal nuclei: caudate nucleus, globus
pallidus, and putamen; complicated interconnections
form a circuit between basal nuclei and other structures
of brain (Figure 12.31):
 Substantia nigra of midbrain works closely with basal
nuclei; often grouped together because of shared
functions
 Basal nuclei modify activity of upper motor neurons to
produce voluntary movements and inhibit involuntary
ones
Figure 12.30 Representations of the primary motor cortex.
© 2016 Pearson Education, Inc.
ROLE OF BRAIN IN VOLUNTARY
MOVEMENT
© 2016 Pearson Education, Inc.
ROLE OF BRAIN IN VOLUNTARY
MOVEMENT
• Role of Basal Nuclei (continued):
 A critical function of basal nuclei is to inhibit
inappropriate movements (Figure 12.31a):
o
In absence of voluntary movement neurons in globus pallidus
fire continuously to inhibit motor nuclei of thalamus
o
Inhibits upper motor neurons of cortical motor areas from
firing
Figure 12.31a Role of the basal nuclei in voluntary movement.
© 2016 Pearson Education, Inc.
ROLE OF BRAIN IN VOLUNTARY
MOVEMENT
• Role of Basal Nuclei (continued):
function of basal nuclei (Figure 12.31b)
o
o
ROLE OF BRAIN IN VOLUNTARY
MOVEMENT
• Role of Basal Nuclei (continued):
 Initiation of voluntary movement is another critical
o
© 2016 Pearson Education, Inc.
If voluntary movement has been initiated, neurons of caudate
nucleus and putamen receive input from cerebral cortex, with
which they form excitatory synapses
These neurons inhibit globus pallidus neurons from firing;
enhanced by substantia nigra (increases output of caudate
nucleus and putamen)
Overall effect – inhibitor (globus pallidus) is inhibited; allows
motor nuclei of thalamus to fire and stimulate upper motor
neurons of cerebral cortex; enables motion
© 2016 Pearson Education, Inc.
 Neurons of substantia nigra are dopaminergic (secrete
dopamine); project to caudate nucleus and putamen
where dopamine enhances inhibitory output to globus
pallidus
 Input of substantia nigra is vital for initiating movement
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ROLE OF BRAIN IN VOLUNTARY
MOVEMENT
ROLE OF BRAIN IN VOLUNTARY
MOVEMENT
• Role of Basal Nuclei (continued):
 Damage to any component of basal nuclei system results
in a movement disorder; two main forms:
o
Inability to initiate voluntary movement, making simple
activities such as walking or talking difficult
o
Inability to inhibit inappropriate, involuntary movements; some
of which are mild (throat clearing or blinking); others may be
severe enough to cause disability
Figure 12.31b Role of the basal nuclei in voluntary movement.
© 2016 Pearson Education, Inc.
ROLE OF BRAIN IN VOLUNTARY
MOVEMENT
© 2016 Pearson Education, Inc.
ROLE OF BRAIN IN VOLUNTARY
MOVEMENT
• Role of the Cerebellum – cerebellum monitors
ongoing movements and integrates information about
contraction and relaxation of muscles, positions of
joints, and direction, force, and type of movement that
is going to occur (Figure 12.32)
 Once information is integrated, cerebellum determines
motor error – difference between intended movement
and actual movement that is taking place
Figure 12.31 Role of the basal nuclei in voluntary movement.
© 2016 Pearson Education, Inc.
ROLE OF BRAIN IN VOLUNTARY
MOVEMENT
• Role of the Cerebellum (continued):
© 2016 Pearson Education, Inc.
ROLE OF BRAIN IN VOLUNTARY
MOVEMENT
• Role of the Cerebellum (continued):
 Cerebellum then influences other regions of brain to
reduce this error; can occur over both short and long
term by a process called motor learning
 Corrections for motor error are added over time to motor
program; more repetition of specific action  more
corrections for motor error added to program  more
fluid and error-free motion becomes
© 2016 Pearson Education, Inc.
 Cerebellum receives input from three sources
simultaneously:
o
motor areas of cerebral cortex via upper motor neurons
o
vestibular nuclei of pons
ascending sensory tracts from spinal cord
o
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ROLE OF BRAIN IN VOLUNTARY
MOVEMENT
• Motor areas provide information on intended
movement, and vestibular nuclei and ascending tracts
supply data on actual movement performed
• Cerebellar neurons process and integrate input from
these sources; send output to correct motor error,
primarily to upper motor neurons via premotor cortex
and primary motor cortex
ROLE OF BRAIN IN VOLUNTARY
MOVEMENT
• Like basal nuclei, cerebellum affects movement by
modifying activity of upper motor neurons; cerebellum
does not have direct connections with lower motor
neurons
• Damage to cerebellum makes fluid, well-coordinated
movements nearly impossible; movements become
jerky and inaccurate; called cerebellar ataxia
© 2016 Pearson Education, Inc.
ROLE OF BRAIN IN VOLUNTARY
MOVEMENT
© 2016 Pearson Education, Inc.
PARKINSON’S DISEASE
• One of most common movement disorders; termed
hypokinetic, meaning that movement is difficult to
initiate and once started, difficult to terminate
 Symptoms – minimal facial expression, shuffling gait
with no arm swing, resting tremor (uncontrollable
shaking movements), difficulty swallowing, and rigid
movements of arms and legs
Figure 12.32 Role of the cerebellum in voluntary movement.
© 2016 Pearson Education, Inc.
PARKINSON’S DISEASE
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THE BIG PICTURE OF CNS CONTROL
OF VOLUNTARY MOVEMENT
• One of most common movement disorders (continued):
 Cause – degeneration of dopamine-secreting neurons of
substantia nigra; progresses slowly over 10–20 years;
underlying mechanism unknown, but genetics suspected
in ~10% of cases
 Treatment – medications that increase level of
dopamine in brain; compensate for decreased level
Figure 12.33 The Big Picture of CNS Control of Voluntary Movement.
© 2016 Pearson Education, Inc.
© 2016 Pearson Education, Inc.
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ROLE OF CNS IN MAINTENANCE
OF HOMEOSTASIS
MODULE 12.7 HOMEOSTASIS PART I:
ROLE OF THE CNS IN MAINTENANCE
OF HOMEOSTASIS
Homeostasis is defined as maintenance of a relatively
stable internal environment in face of ever-changing
conditions
• Homeostatic functions include maintaining fluid,
electrolyte, and acid-base balance; blood pressure;
blood glucose and oxygen concentrations; biological
rhythms; and body temperature
© 2016 Pearson Education, Inc.
ROLE OF CNS IN MAINTENANCE
OF HOMEOSTASIS
•
Nervous system and endocrine system are main systems
dedicated to maintaining homeostasis; work together but
each has its own mechanisms for performing vital
homeostatic regulation
 Endocrine system secretes hormones into blood; regulates
functions of other cells
 Nervous system sends action potentials; excite or inhibit
target cells
 Actions of endocrine system are typically slow (take several
hours or even days to have an effect) whereas actions of
nervous system are generally immediate
© 2016 Pearson Education, Inc.
© 2016 Pearson Education, Inc.
ROLE OF CNS IN MAINTENANCE
OF HOMEOSTASIS
• Two structures of CNS are concerned directly with
maintenance of homeostasis:
 Reticular formation – controls functions of many
internal organs as well as aspects of behavior
 Hypothalamus – closely associated (anatomically and
functionally) with pituitary gland; reflects close
relationship between these vital systems
 Reticular formation and hypothalamus have many
interconnections; enable them to coordinate many
homeostatic functions
© 2016 Pearson Education, Inc.
HOMEOSTASIS OF VITAL
FUNCTIONS
HOMEOSTASIS OF VITAL
FUNCTIONS
• Maintenance of vital functions (heart pumping, blood
• Although ANS is a component of PNS it is controlled
pressure, and digestion) is largely controlled by
autonomic nervous system (ANS); regulates function
of body’s viscera
• Although ANS is a component of PNS it is controlled
by components of CNS, mainly hypothalamus
by components of CNS, mainly hypothalamus
(continued):
 Hypothalamus receives sensory input from viscera,
components of the limbic system, and the cerebral cortex
 Allows hypothalamus to respond to both normal
physiological changes and emotional changes and to
adjust ANS output to maintain homeostasis
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HOMEOSTASIS OF VITAL
FUNCTIONS
• Hypothalamus maintains homeostasis largely by
relaying instructions to nuclei in reticular formation of
medulla; include following centers:
 Neurons of vasopressor center – located in anterolateral
medulla; when stimulated by hypothalamus, center
increases rate and force of cardiac contractions and
causes blood vessels to narrow; increases blood
pressure
HOMEOSTASIS OF VITAL
FUNCTIONS
• Hypothalamus maintains homeostasis largely by
relaying instructions to nuclei in reticular formation of
medulla; include following centers (continued):
 Vasodepressor center – located inferior and medial to
vasopressor center; decreases rate and force of heart
contractions and opens blood vessels; all three effects
decrease blood pressure
 Other centers: many nuclei in reticular formation
participate in regulation of digestive processes and
control of urination
© 2016 Pearson Education, Inc.
HOMEOSTASIS OF VITAL
FUNCTIONS
• Respiration is one of few vital functions not under
ANS control
© 2016 Pearson Education, Inc.
BODY TEMPERATURE
HOMEOSTASIS
• Hypothalamus regulates body temperature
 Acts as body’s thermostat; creates a set point for normal
 Rate and depth of breathing are regulated by group of
neurons in anterior medullary reticular formation
 Several factors influence neuron firing rates: input from
cerebral cortex, limbic system, hypothalamus, certain
sensory receptors, and nuclei in pons
body temperature, about 37 C or 98.6 F
 Input is received from temperature-sensitive neurons
located in several places (skin and areas deeper in body)
and from neurons in hypothalamus itself
© 2016 Pearson Education, Inc.
© 2016 Pearson Education, Inc.
BODY TEMPERATURE
HOMEOSTASIS
FEVER
• Hypothalamus regulates body temperature (continued):
• Elevation of body temperature can accompany variety
 When body temperature increases above set point, a
negative feedback loop is initiated whereby certain
hypothalamic nuclei induce changes that cool body
 When body temperature decreases below set point, a
different feedback loop is initiated that conserves heat
 Both are examples of Feedback Loops Core Principle
 Fever ensues when body temperature set point is
temporarily set higher than normal
© 2016 Pearson Education, Inc.
of infectious and noninfectious conditions
• Caused by pyrogens (chemicals) secreted by cells of
immune system and by certain bacteria; cross bloodbrain barrier and interact with nuclei of hypothalamus
(control temperature)
• Pyrogens increase hypothalamic set point to higher
temperature; feedback loop triggers shivering and
muscle aches due to increased muscle tone; constricts
blood vessels serving skin
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FEVER
REGULATION OF FEEDING
• Treatment is not always necessary; often more
important to address underlying cause
• Hypothalamus also regulates feeding
 Stimulation of certain hypothalamic nuclei induces
• Antipyretics – used to treat fever; include
acetaminophen and aspirin; work by blocking
formation of pyrogens; permits hypothalamus to return
to normal set point
hunger and feeding behaviors; indirectly preserves
homeostasis of glucose
 Thought to be related to secretion of neurotransmitters
called orexins
© 2016 Pearson Education, Inc.
REGULATION OF FEEDING
• Hypothalamus also regulates feeding (continued):
 Orexins are secreted by hypothalamic neurons during
periods of fasting; appear to induce eating; also play an
important role regulating sleep/wake cycle
 Stimulation of different hypothalamic nuclei seems to
inhibit feeding; mechanisms controlling food intake are
complex and involve hormones, several hypothalamic
nuclei, and other regions of brain
© 2016 Pearson Education, Inc.
SLEEP AND WAKEFULNESS
• Sleep, defined as a reversible and normal suspension of
consciousness; one of most fundamental homeostatic
processes carried out by humans and most other
animals
 Information is known pertaining to how we sleep, how
sleep is regulated, and brain activity during sleep, but
why most animals sleep is as yet unknown
 Physiologically, sleep appears to serve an energy
restoration function; allows brain to replenish its
glycogen supply
© 2016 Pearson Education, Inc.
SLEEP AND WAKEFULNESS
• Sleep (continued):
© 2016 Pearson Education, Inc.
SLEEP AND WAKEFULNESS
• Sleep (continued):
 Sleep is required for survival; deprivation can cause
imbalances in temperature homeostasis, weight loss, a
decrease in cognitive abilities, hallucinations, and even
death
 Most adults only require 7–8 hours of sleep while
 Circadian Rhythms and Biological “Clock”: Human
sleep follows a circadian rhythm
o
We spend a period of cycle awake and remainder asleep
o
Rhythm is controlled by hypothalamus; causes changes in level
of wakefulness in response to day and night cycles
infants require about 17 hours per night
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© 2016 Pearson Education, Inc.
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SLEEP AND WAKEFULNESS
• Sleep occurs in following sequence of events (Figure
12.34):
SLEEP AND WAKEFULNESS
• Sleep (continued):
 Decreased activity of reticular formation “disconnects”
 Nerves from eye signal suprachiasmatic nucleus
(SCN) of hypothalamus that light level is decreasing
 SCN stimulates ventrolateral preoptic nucleus
(hypothalamus); stimulates pineal gland to secrete
melatonin
thalamus from cerebral cortex; decreases level of
consciousness
 Arousal from sleep is mediated by a different group of
hypothalamic neurons; secrete neurotransmitter orexin;
example of Cell-Cell Communication Core Principle
 Ventrolateral preoptic nucleus decreases activity of
reticular formation
© 2016 Pearson Education, Inc.
SLEEP AND WAKEFULNESS
© 2016 Pearson Education, Inc.
SLEEP AND WAKEFULNESS
• Brain Waves and Stages of Sleep – stages of sleep
can be monitored using electroencephalogram (EEG);
measure electrical activity of brain using electrodes
attached to skin (Figure 12.35)
 Tracings of electrical activity (brain waves) show
characteristic patterns during wakefulness and different
stages of sleep
 Waves differ in height (amplitude) and speed at which
they are generated (frequency)
Figure 12.34 The process of falling asleep.
© 2016 Pearson Education, Inc.
© 2016 Pearson Education, Inc.
SLEEP AND WAKEFULNESS
SLEEP AND WAKEFULNESS
• Brain Waves and Stages of Sleep (continued):
• Brain Waves and Stages of Sleep (continued):
 Beta waves – low amplitude and high frequency; occur
when we are awake and engaged in mental activity
 Stages I–III sleep are characterized by drowsiness
progressing to moderately deep sleep; betas waves slow
to theta waves with progressively decreasing frequency
(and increasing amplitude)
© 2016 Pearson Education, Inc.
 State IV sleep is deepest stage with characteristic low-
frequency, high-amplitude delta waves; stages I–IV
collectively is known as non-REM sleep or non-rapid
eye movement sleep
 REM sleep (rapid eye movement) lasts for 10–15
minutes and occurs after stage IV sleep; known for back
and forth eye movements; stage where most dreaming
occurs; REM waves resemble beta waves of wakefulness
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STATES OF ALTERED
CONSCIOUSNESS MIMICKING SLEEP
SLEEP AND WAKEFULNESS
• Altered consciousness can indicate serious problems
with brain function; examples include:
 Stupor – diminished level of cortical activity; arousable
with strong/painful stimuli; caused by infections, mental
illnesses, and brain conditions (such as brain tumors)
 Coma – unarousable unconsciousness; no purposeful
responses to any stimuli (even pain); underlying defect
is damage to reticular activating system or related
component; prohibits normal arousal of cerebral cortex
Figure 12.35 Stages of wakefulness and sleep as shown by EEG patterns.
© 2016 Pearson Education, Inc.
© 2016 Pearson Education, Inc.
STATES OF ALTERED
CONSCIOUSNESS MIMICKING SLEEP
STATES OF ALTERED
CONSCIOUSNESS MIMICKING SLEEP
• Altered consciousness can indicate serious problems
• Altered consciousness can indicate serious problems
with brain function; examples include (continued):
with brain function; examples include (continued):
 Persistent vegetative state – some patients move from
 Coma (continued):
o
o
o
EEG demonstrates slow, fixed pattern with no observable
sleep/wake cycles
Brainstem reflexes remain intact; certain patients exhibit
involuntary movements
coma state to condition where they are awake but
unaware because of damage to cerebral cortex; also lack
voluntary movement
o
Sleep/wake cycles do occur; brainstem reflexes remain intact,
leading to involuntary movements (head turning and grunt-like
vocalizations)
o
Can be misinterpreted as meaningful but not mediated by
cortex, thus do not imply conscious awareness
May result from head trauma, certain drugs, disturbances in
acid-base homeostasis and various neurological conditions
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© 2016 Pearson Education, Inc.
STATES OF ALTERED
CONSCIOUSNESS MIMICKING SLEEP
• People in altered states of consciousness may
occasionally regain consciousness, depending on cause
of state
• Brain death – most extreme state of altered
consciousness; EEG shows no activity; brainstem
reflexes are absent; cerebral blood flow and
metabolism are reduced to zero; consciousness will not
be regained
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MODULE 12.8 HIGHER MENTAL
FUNCTIONS
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COGNITION AND LANGUAGE
COGNITION AND LANGUAGE
• Cognition – collective term for diverse group of tasks;
• Localization of Cognitive Function – following areas
performed by association areas of cerebral cortex
 Cognitive functions – include processing and
responding to complex external stimuli, recognizing
related stimuli, processing internal stimuli, and planning
appropriate responses to stimuli
 Cognitive processes – responsible for social and moral
behavior, intelligence, thoughts, problem-solving skills,
language, and personality
and their functions are involved in cognition:
 Parietal association cortex – responsible for spatial
awareness and attention; allows us to focus on distinct
aspects of a specific object and recognize position of
object in space
 Temporal association cortex – primarily responsible
for recognizing stimuli, especially complex stimuli such
as faces
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COGNITION AND LANGUAGE
• Localization of Cognitive Function (continued):
 Prefrontal cortex – largest and most complex of
association cortices
o
Responsible for majority of cognitive functions that make up a
person’s “character” or “personality”
o
Gathers information from other association cortices and from
other sensory and motor cortices and integrates information to
create an awareness of “self”
o
Allows for planning and execution of behaviors appropriate for
given circumstances
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COGNITION AND LANGUAGE
• Cerebral lateralization – phenomenon in which many
cognitive functions are unequally represented in right
and left hemispheres
 Represents a division of labor between hemispheres to
maximize a limited amount of brain space
 Following functions appear to be lateralized although
this is not an absolute (next slide)
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COGNITION AND LANGUAGE
• Cerebral lateralization (continued):
this is not an absolute (continued):
o
o
DEMENTIA
• Patients with dementia exhibit a progressive loss of
 Following functions appear to be lateralized although
o
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Emotional functions – left frontal cortex is mostly responsible
for “positive” emotions while right cortex for “negative”
emotions
Attention is lateralized to right parietal cortex while facial
recognition is lateralized in right temporal cortex
Language-related recognition and ability to identify an object
with its proper name are lateralized in left temporal cortex
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recent memory, degeneration of cognitive functions,
and changes in personality
• No proven method for prevention or cure of dementia
exists; some drugs may slow progression of
Alzheimer’s disease in certain patients but do not
reverse changes that already exist; ineffective in other
forms of dementia
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DEMENTIA
DEMENTIA
• Common (most to least) forms of dementia include:
• Common (most to least) forms of dementia include
(continued):
 Alzheimer’s disease (AD)
o
o
 Vascular dementia
Neurofibrillary tangles (aggregates of proteins in neurons),
senile plaques (extracellular deposits of specific protein
around neurons), and degeneration of cortical neurons and
synaptic connections occur throughout brain; especially
numerous in cortical association areas and hippocampus
Earliest signs are recent memory loss and forgetfulness;
progresses to impairment of attention, language skills, critical
thinking and visual-spatial abilities, and changes in personality;
eventually motor skills, sensory perception, and long-term
memory are affected
o
o
o
Group of diseases; share common feature of disruption in
blood flow to parts of brain, particularly cerebral cortex
Signs and symptoms are highly variable because of range of
brain regions affected
Significant overlap with AD; patients often have both forms;
known as mixed dementia
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© 2016 Pearson Education, Inc.
DEMENTIA
DEMENTIA
• Common (most to least) forms of dementia include
• Common (most to least) forms of dementia include
(continued):
(continued):
 Pick’s disease
 Lewy body dementia
o
o
Cytoplasmic inclusions (Lewy bodies) in neurons of certain
brain parts
Fluctuation in cognitive functions, impaired memory
formation, hallucinations, delusions, sleep disorders, and motor
features of Parkinson’s disease
o
o
o
o
Cerebral cortex of frontal and temporal lobes progressively
degenerates
Results in severe atrophy due to loss of neurons with excess
neuroglia
Unusual, in that younger population affected (age 55–65)
Patients deteriorate rapidly; dramatic personality changes and
behavioral problems common because of prefrontal cortex
involvement
© 2016 Pearson Education, Inc.
© 2016 Pearson Education, Inc.
COGNITION AND LANGUAGE
• Language, arguably one of most important cognitive
functions of brain; refers to ability to comprehend and
produce words through speaking, writing, and/or
signing, and to assign and recognize symbolic meaning
of a word correctly
COGNITION AND LANGUAGE
•
Multiple brain regions are required for communication but
two multimodal association areas are critical (Figure
12.36):
 Broca’s area – in frontal lobe; responsible for production of
language, including planning and ordering of words with
proper grammar and syntax
 Wernicke’s area – in temporal lobe; responsible for
understanding language and linking a word with its correct
symbolic meaning
 Aphasia – language deficit; occurs when either of these two
critical areas is damaged
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COGNITION AND LANGUAGE
APHASIAS
• Aphasia (language deficits)
 Broca’s – inability to correctly plan and order grammar
and syntax; words and phrases repeated; grammar,
syntax, and structure of individual words are disordered;
frustrating for patients because language comprehension
is intact
 Wernicke’s – inability to understand language; speak
Figure 12.36 Functional neuroimaging (functional magnetic resonance imaging, fMRI) of
the brain during speech.
fluently with adequate grammar and syntax but words
and meanings are not correctly linked; cannot realize
that what they are saying makes no sense; language
comprehension is not intact
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LEARNING AND MEMORY
• Two basic types of memory: declarative (fact) memory
– defined as memory of things that are readily available
to consciousness; could in principle be expressed aloud
(hence term “declarative”), and nondeclarative
memory (procedural or skills memory); includes skills
and associations that are largely unconscious
 Declarative examples – phone number, a quote, or
pathway of corticospinal tracts
 Nondeclarative examples – how to enter phone number
on a phone, how to move your mouth to speak, and how
to read this chapter
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© 2016 Pearson Education, Inc.
LEARNING AND MEMORY
• Declarative and nondeclarative memory can be
classified by length of time in which they are stored:
 Immediate memory – stored only for a few seconds; is
critical for carrying out normal conversation, reading,
and daily tasks
 Short-term (working) memory – stored for several
minutes; allows you to remember and manipulate
information with a general behavioral goal in mind
 Long-term memory – a more permanent form of
storage for days, weeks, or even a lifetime
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LEARNING AND MEMORY
LEARNING AND MEMORY
• Process of converting immediate or working memory
• Long-term potentiation (LTP) – mechanism by which
into long-term memory involves a process called
consolidation (Figure 12.37)
• Formation and storage of declarative memory
appears to require hippocampus (component of limbic
system); immediate and short-term memories are likely
stored in this region
hippocampal neurons encode long-term declarative
memories, seems to involve an increase in synaptic
activity between associated neurons; example of CellCell Communication Core Principle
 Although hippocampus is required to form new
declarative memories, long-term memories are not
stored in this region; stored in cerebral cortex that
correlates with their functions
 Retrieval of memories seems to be mediated by
pathways involving hippocampus and prefrontal cortex
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LEARNING AND MEMORY
LEARNING AND MEMORY
• Formation and storage of nondeclarative memory
doesn’t rely on hippocampus; memories seem to be
stored in cerebral cortex, cerebellum, and basal nuclei
Figure 12.37 Pathways for consolidation of memories.
© 2016 Pearson Education, Inc.
© 2016 Pearson Education, Inc.
LEARNING AND MEMORY
• Emotion – complex combination of three separate
phenomena:
LEARNING AND MEMORY
• Emotion (continued):
 “Feelings” – highly subjective; most complex;
 Visceral motor responses – blushing or heart racing;
mediated by hypothalamus
 Somatic motor responses – smiling, laughing,
frowning, and crying; mediated by hypothalamus and
limbic cortex through reticular formation
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integrated with sensory and/or cognitive stimuli
o
Feeling sad when remembering a lost pet or feeling tense when
watching a suspenseful movie
o
Amygdala receives input from brainstem, thalamus, cerebral
cortex, and basal nuclei, analyzes emotional significance of
stimuli; creates associations between different stimuli; projects
to prefrontal cortex
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