Download CHAPTER 12: THE CENTRAL NERVOUS SYSTEM MODULE 12.1

CHAPTER 12: THE CENTRAL NERVOUS SYSTEM
MODULE 12.1 OVERVIEW OF THE CENTRAL NERVOUS SYSTEM
CENTRAL NERVOUS SYSTEM

Central nervous system (CNS) – includes brain and spinal cord; involved in
movement, interpreting sensory information, maintaining homeostasis, and functions
relating to mind
OVERVIEW OF CNS FUNCTIONS

Functions of nervous system can be broken down into 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
OVERVIEW OF CNS FUNCTIONS

Functions of nervous system (continued):
 Integrative functions – include decision-making processes; exclusive function of
CNS; includes a wide variety of functions:
o Interpretation of sensory information
o Planning and monitoring movement
o Maintenance of homeostasis
o Higher mental functions such as language and learning
BASIC STRUCTURE OF THE BRAIN AND SPINAL CORD

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
BASIC STRUCTURE OF THE BRAIN AND SPINAL CORD

Brain consists of four divisions, each distinct in type of input it receives and where it
sends its output:
 Cerebrum
 Diencephalon
 Cerebellum
 Brainstem
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BASIC STRUCTURE OF THE BRAIN AND SPINAL CORD

Cerebrum – enlarged superior portion of brain; divided into left and right cerebral
hemispheres
 Each cerebral hemisphere is further divided into five lobes containing groups of
neurons that perform specific tasks
 Responsible for higher mental function such as learning, memory, personality,
cognition (thinking), language, and conscience
 Performs major roles in sensation and movement as well
BASIC STRUCTURE OF THE BRAIN AND SPINAL CORD

Diencephalon – deep underneath cerebral hemispheres; central core of brain
 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
BASIC STRUCTURE OF THE BRAIN AND SPINAL CORD

Cerebellum – posterior and inferior portion of brain
 Divided into left and right hemispheres
 Heavily involved in planning and coordination of movement, especially complex
activities such as playing a sport or an instrument
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
BASIC STRUCTURE OF THE BRAIN AND SPINAL CORD

Spinal cord – long tubular organ enclosed within 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
BASIC STRUCTURE OF THE BRAIN AND SPINAL CORD

White matter – found in both brain and spinal cord; 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

Gray matter – found in both brain and spinal cord; 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 information (in cord center);
surrounded by tracts of white matter (outside); relays information to and from
brain
BASIC STRUCTURE OF THE BRAIN AND SPINAL CORD


Communication between gray and white matter 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
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
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:
 Forebrain expands into two secondary brain vesicles (telencephalon and
diencephalon); two lobes of telencephalon become cerebral hemispheres;
diencephalon retains its name in mature brain
OVERVIEW OF CNS DEVELOPMENT

Secondary brain vesicles create four divisions of mature brain (continued):
 Midbrain expands into secondary brain vesicle called mesencephalon; develops
into mature midbrain
 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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MODULE 12.2 THE BRAIN
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
THE CEREBRUM

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
THE CEREBRUM

Five lobes are found in each hemisphere of cerebrum (Figure 12.4):
 Frontal lobe
 Parietal lobe
 Temporal lobe
 Occipital lobe
 Insula
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
THE CEREBRUM

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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THE CEREBRUM

Five lobes of cerebrum (continued):
 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
THE CEREBRUM

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
THE CEREBRUM

Five lobes of cerebrum (continued):
 Insulas – deep underneath lateral fissures; neurons in these lobes are currently
thought to be involved in functions related to taste and viscera (internal organs)
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
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
 Neocortex is divided into three areas: primary motor cortex, primary sensory
cortices, and association areas (next slide)
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 Primary motor cortex – plans and executes movement
o Primary sensory cortices – first regions to receive and process sensory input
o 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
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 control motor activity of opposite
side of body via PNS neurons called lower motor neurons; execute order to move
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
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
THE CEREBRUM-GRAY MATTER
Sensory Cortices (continued):
 Special senses – touch, vision, hearing, smell, and taste 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 lobe; first area to receive
visual input; transferred to visual association area which processes color, object
movement, and depth
THE CEREBRUM-GRAY MATTER
Sensory Cortices (continued):
 Special senses (continued):
 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
THE CEREBRUM-GRAY MATTER
Sensory Cortices (continued):
 Special senses (continued):
 Gustatory cortex – taste information processing; scattered throughout both
insula and parietal lobes
 Vestibular areas – deal with equilibrium and positional sensations; located in
parietal and temporal lobes
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THE CEREBRUM-GRAY MATTER
Sensory Cortices (continued):
 Special senses (continued):
 Olfactory cortex – processes sense of smell; in evolutionarily older regions of
brain; consists of several areas in limbic and medial temporal lobes
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
THE CEREBRUM-GRAY MATTER
Multimodal association areas (continued):
 Prefrontal cortex occupies most of frontal lobe; 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
THE CEREBRUM-GRAY MATTER
Multimodal association areas (continued):
 Parietal and temporal association areas – occupy most of their respective lobes;
perform multiple functions including integration of sensory information, language,
maintaining attention, recognition, and spatial awareness
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
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
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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
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
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
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 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
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
THE DIENCEPHALON

Thalamus (continued):
 Regulates cortical activity by controlling which input should continue to cerebral
cortex
 Each half of thalamus has three main groups of nuclei separated by thin layers of
white matter
 Specific nuclei function as relay stations that receive input, integrate information,
then send information to specific motor or sensory areas in cerebral cortex
THE DIENCEPHALON

Thalamus (continued):
 Association nuclei
o Receive input from variety of sources
o Process information related to emotions, memory, and integration of sensory
information
o Processed information is sent on to appropriate association areas of cerebral
cortex
THE DIENCEPHALON

Thalamus (continued):
 Nonspecific nuclei
o Receive information from basal nuclei, cerebellum, and motor cortex
o Send information to a wide range of locations including cerebral cortex and
other brain regions
o Involved in controlling arousal, consciousness, and level of responsiveness
and excitability of cerebral cortex
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THE DIENCEPHALON

Hypothalamus – collection of nuclei anterior and inferior to larger thalamus
 Neurons perform several vital functions critical to survival; include regulation of
autonomic nervous system, sleep/wake cycle, thirst and hunger, and body
temperature
THE DIENCEPHALON

Hypothalamus (continued):
 Inferior hypothalamus – anatomically and functionally linked to pituitary gland
by an extension called infundibulum; hypothalamic tissue makes up posterior
portion of this endocrine gland
 Hypothalamus secretes a number of different releasing and inhibiting hormones;
affect function of pituitary gland; in turn, pituitary gland secretes hormones that
affect activities of other endocrine glands throughout body
THE DIENCEPHALON

Hypothalamus (continued):
 Antidiuretic hormone and oxytocin, hypothalamic hormones that do not affect
pituitary gland, have their effect on water balance and stimulation of uterine
contraction during childbirth, respectively
 Input to hypothalamus arrives from many sources including cortex and basal
nuclei
THE DIENCEPHALON

Hypothalamus (continued):
 Mammillary bodies – connect hypothalamus with limbic system; receive input
from hippocampus; involved in memory regulation and behavior
 Input from outside nervous system; endocrine system (among others) provides
information from receptors that detect changes in body temperature and receptors
that detect changes in osmotic concentration of blood
THE DIENCEPHALON


Epithalamus – superior to thalamus; most of its posterosuperior bulk is an endocrine
gland called pineal gland; secretes melatonin; hormone involved in sleep/wake cycle
Subthalamus – inferior to thalamus; functionally connected with basal nuclei;
together, they control movement
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
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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
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
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
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
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
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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THE BRAINSTEM

Midbrain
 Inferior to diencephalon; surrounds cerebral aqueduct (connects third and fourth
ventricles) (Figure 12.14b)
 Also known as mesencephalon; shortest and most superior brainstem region
THE BRAINSTEM

Midbrain (continued):
 Includes following structures:
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
o Descending tracts – white matter tracts that originate in cerebrum and form
anteriormost portion of midbrain; called crus cerebri
THE BRAINSTEM

Midbrain (continued):
 Includes following structures (continued):
o Substantia nigra – posterior to crus cerebri, is a darkly pigmented region
whose neurons work with basal nuclei to control movement
o Red nucleus – posterior to substantia nigra; communicates with cerebellum,
spinal cord, and other regions involved in regulating movement; role in
humans not yet understood
THE BRAINSTEM

Midbrain (continued):
 Includes following structures (continued):
o Many cranial nerve nuclei are found in midbrain
o 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
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
 Reticular formation and cranial nerve nuclei are located posterior to these tracts
THE BRAINSTEM

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
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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
THE BRAINSTEM

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
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
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
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
13
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
MODULE 12.3 PROTECTION OF THE BRAIN
BRAIN PROTECTION
Three features within protective shell of skull provide additional shelter for delicate brain
tissue:
 Cranial meninges – three layers of membranes that surround brain
 Cerebrospinal fluid (CSF) – fluid that bathes brain and fills cavities
 Blood-brain barrier – prevents many substances from entering brain and its cells
from blood
BRAIN PROTECTION

Cranial meninges – composed of three protective membrane layers of mostly dense
irregular collagenous tissue
 Structural arrangement from superficial to deep: epidural space, dura mater,
subdural space, arachnoid mater, subarachnoid space, and pia mater (Figure
12.18)
BRAIN PROTECTION

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) – outermost meninx; thickest and most durable of three
meningeal layers; double-layered membrane composed mostly of collagen fibers
with few elastic fibers
BRAIN PROTECTION

Cranial meninges (continued):
 Dura mater (dura) (continued):
o 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
14
•
Mostly fused, creating a single inelastic membrane except in regions
where cavities called dural sinuses are found
BRAIN PROTECTION

Cranial meninges (continued):
 Dura mater (dura) (continued):
o 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
BRAIN PROTECTION

Cranial meninges (continued):
 Dura mater (dura) (continued):
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
BRAIN PROTECTION

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 subdural space; thin weblike
membrane composed of dense irregular collagenous tissue with some degree of
elasticity (Figure 12.18c)
BRAIN PROTECTION

Cranial meninges (continued):
 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
BRAIN PROTECTION

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
15
tissue
BRAIN PROTECTION

Cranial meninges (continued):
 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
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)
 Lined with ependymal cells
 Filled with cerebrospinal fluid
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; horseshoe-shaped
appearance in lateral view
 Three regions: anterior horn, inferior horn, and posterior horn
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)
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 within cranial cavity
 Removes wastes and increases buoyancy of brain; keeps brain from collapsing
under its own weight
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 cells; allow fluids and
electrolytes to exit from blood plasma to enter extracellular fluid (ECF)
16
THE VENTRICLES AND CEREBROSPINAL FLUID

Choroid plexuses (continued):
 About 150 ml (2/3 cup) of CSF circulates through brain and spinal cord
 750–800 ml of CSF is produced daily so old CSF must be removed as choroid
plexuses make new CSF
 Process of CSF production and removal occurs constantly; CSF is completely
replaced every 5–6 hours
THE VENTRICLES AND CEREBROSPINAL FLUID

Pathway for formation, circulation, and reabsorption of CSF (Figure 12.20):
 Fluid and electrolytes leak out of capillaries of choroid plexuses into ECF of
ventricles
 Taken up into ependymal cells; then secreted into ventricles as CSF
 Circulated through and around brain and spinal cord in subarachnoid space;
assisted by movement of ependymal cell cilia
 Some CSF is reabsorbed into venous blood in dural sinuses via arachnoid
granulations
THE BLOOD-BRAIN B ARRIER
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
THE BLOOD-BRAIN B ARRIER

Unique features of endothelial cells found in barrier:
 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
THE BLOOD-BRAIN B ARRIER



Substances that easily pass through plasma membranes are able to pass through
blood-brain barrier; include water, oxygen, carbon dioxide, and nonpolar, lipid-based
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
17
CONCEPT BOOST: WHERE EXACTLY IS BLOOD-BRAIN B ARRIER?



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
CONCEPT BOOST: WHERE EXACTLY IS BLOOD-BRAIN B ARRIER?



Capillaries found in most organs and tissues are fairly 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
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:
 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
MODULE 12.4 THE SPINAL CORD
THE SPINAL CORD

Spinal cord – composed primarily of nervous tissue; 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
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)
18
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
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):
 Epidural space – actual space due to absence of a periosteal dura; found between
meningeal dura and walls of vertebral foramina; space is filled with veins and
adipose tissue; cushions and protects spinal cord
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):
 Subdural space – only a potential space much like 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
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,
encephalitisand multiple sclerosis
19
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):
 Narrow posterior median sulcus can be seen on entire length of posterior side of
cord
 Wider anterior median sulcus can be seen on entire length of anterior side of cord
 Conus medullaris is cone-shaped distal end of cord
EXTERNAL SPINAL CORD ANATOMY


Filum terminale – found between first and second 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
Spinal cord has two enlarged regions (cervical and lumbar enlargements); nerve
roots fuse together to form spinal nerves (serve upper and lower extremities
respectively) in these enlargements (Figure 12.23a)
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
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):
 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
INTERNAL SPINAL CORD ANATOMY


Anterior to posterior orientation of spinal cord can be determined by using shape and
size of gray matter wings
Anterior wings are broader while thinner posterior wings extend almost to outer
surface of spinal cord
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)
20
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
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)
INTERNAL SPINAL CORD ANATOMY

Spinal White Matter (continued):
 Funiculi features
o 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
INTERNAL SPINAL CORD ANATOMY

Spinal White Matter (continued):
 Ascending tracts carry various kinds of sensory 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
INTERNAL SPINAL CORD ANATOMY

Spinal White Matter (continued):
 Ascending tracts (continued):
o Spinocerebellar tracts – found in lateral funiculi; carry information about
joint position and muscle stretch from entire body to cerebellum
o Anterolateral system includes spinothalamic tracts that travel in anterior
and lateral funiculi; transmit pain and temperature stimuli from entire body to
brain
21
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
o Travel through lateral funiculi of spinal cord; fibers deliver motor information
to appropriate locations in anterior horn
MODULE 12.5 SENSATION PART I:
ROLE OF THE CNS IN SENSATION
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
 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
SENSORY STIMULI

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 Special senses – detected by special sense organs and include vision, hearing,
equilibrium, smell, and taste
o 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
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
22
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
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
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)
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
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
23
GENERAL SOMATIC SENSES

Role of Cerebral Cortex in Sensation, S1 and Somatotopy:
 Thalamus relays most incoming information to primary somatosensory cortex
(S1) in postcentral gyrus
 Each part of body is represented by a specific region of S1, a type of organization
called somatotopy (Figure 12.28)
GENERAL SOMATIC SENSES

Role of Cerebral Cortex (continued):
 Mapping of primary somatosensory cortex (S1) illustrates that different parts of
body are unequally represented (Figure 12.28a)
 More S1 space is dedicated to hands and face; represents 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)
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
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
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
24
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
GENERAL SOMATIC SENSES

Role of the Cerebral Cortex in Sensation – Processing of Pain Stimuli
(continued):
 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
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 Pain input is still present and its intensity is unaffected
o CNS neurons perceive pain as being less intense (or absent)
o 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
INTRODUCTION TO SPECIAL SENSES

Special senses include vision, hearing (audition), taste (gustation), smell
(olfaction), and balance (vestibular sensation)
 Each involves neurons that detect a stimulus and send it to CNS for processing
and integration
 Thalamus – gateway for entry of special sensory stimuli into cerebral cortex;
interprets majority of this information; olfaction is exception
25
INTRODUCTION TO SPECIAL SENSES

Special senses include vision, hearing (audition), taste (gustation), smell
(olfaction), and balance (vestibular sensation) (continued):
 Pathways for processing each type of special sensory stimuli:
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
INTRODUCTION TO SPECIAL SENSES

Special senses include vision, hearing (audition), taste (gustation), smell
(olfaction), and balance (vestibular sensation) (continued):
 Pathways for processing each type of special sensory stimuli (continued):
o Auditory
• Stimuli first go to nuclei in brainstem where limited processing occurs
• Majority of stimuli are routed to thalamus and then primary auditory
cortex (superior temporal lobe), for sound processing
• Information is relayed to other association areas such as Wernicke’s area
for language comprehension
INTRODUCTION TO SPECIAL SENSES

Special senses include vision, hearing (audition), taste (gustation), smell
(olfaction), and balance (vestibular sensation) (continued):
 Pathways for processing each type of special sensory stimuli (continued):
o Gustatory
• Stimuli are sent to nuclei in medulla before being relayed to thalamus
• Then sent to gustatory cortices (insula and parietal lobes) for processing
• Information is sent to hypothalamus and limbic system likely for
processing of taste preferences and food-seeking behaviors
INTRODUCTION TO SPECIAL SENSES

Special senses include vision, hearing (audition), taste (gustation), smell
(olfaction), and balance (vestibular sensation) (continued):
 Pathways for processing each type of special sensory stimuli (continued):
o Olfactory
• 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
26
INTRODUCTION TO SPECIAL SENSES

Special senses include vision, hearing (audition), taste (gustation), smell
(olfaction), and balance (vestibular sensation) (continued):
 Pathways for processing each type of special sensory stimuli (continued):
o Balance
• Processing vestibular stimuli involves several brainstem nuclei,
cerebellum, descending pathways through spinal cord, and pathways
through thalamus to cerebral cortex
MODULE 12.6 MOVEMENT PART I: ROLE OF THE CNS
IN VOLUNTARY MOVEMENT
VOLUNTARY MOVEMENT


Planning and coordination of voluntary movement are 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)
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
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
 Axons unite and descend through corona radiata and internal capsule on way to
brainstem (midbrain and pons)
27
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
 Fibers that decussate travel in lateral funiculi; are then known as right and left
lateral corticospinal tracts
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
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
 Do not enter spinal cord; instead synapse on interneurons that communicate with
cranial nerve nuclei at various levels of 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 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
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)
 Firing of lower motor neurons in PNS is necessary to complete task
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
28
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)
ROLE OF BRAIN IN VOLUNTARY MOVEMENT

Role of Cerebral Cortex (continued):
 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
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
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
ROLE OF BRAIN IN VOLUNTARY MOVEMENT

Role of Basal Nuclei (continued):
 Initiation of voluntary movement is another critical function of basal nuclei
(Figure 12.31b)
o If voluntary movement has been initiated, neurons of caudate nucleus and
putamen receive input from cerebral cortex, with which they form excitatory
synapses
o These neurons inhibit globus pallidus neurons from firing; enhanced by
substantia nigra (increases output of caudate nucleus and putamen)
o Overall effect – inhibitor (globus pallidus) is inhibited; allows motor nuclei
of thalamus to fire and stimulate upper motor neurons of cerebral cortex;
enables motion
29
ROLE OF BRAIN IN VOLUNTARY MOVEMENT

Role of Basal Nuclei (continued):
 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
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
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
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
ROLE OF BRAIN IN VOLUNTARY MOVEMENT

Role of the Cerebellum (continued):
 Cerebellum receives input from three sources simultaneously:
o motor areas of cerebral cortex via upper motor neurons
o vestibular nuclei of pons
o ascending sensory tracts from spinal cord
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
30
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
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
PARKINSON’S DISEASE

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
MODULE 12.7 HOMEOSTASIS PART I: ROLE OF THE CNS
IN M AINTENANCE OF HOMEOSTASIS
ROLE OF 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
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
31
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
HOMEOSTASIS OF VITAL FUNCTIONS


Maintenance of vital functions (heart pumping, blood 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
HOMEOSTASIS OF VITAL FUNCTIONS

Although ANS is a component of PNS it is controlled 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
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
HOMEOSTASIS OF VITAL FUNCTIONS

Respiration is one of few vital functions not under ANS control
 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
32
BODY TEMPERATURE HOMEOSTASIS

Hypothalamus regulates body temperature
 Acts as body’s thermostat; creates a set point for normal 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
BODY TEMPERATURE HOMEOSTASIS

Hypothalamus regulates body temperature (continued):
 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
FEVER



Elevation of body temperature can accompany variety of infectious and noninfectious
conditions
Caused by pyrogens (chemicals) secreted by cells of immune system and by certain
bacteria; cross blood-brain 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
FEVER


Treatment is not always necessary; often more important to address underlying cause
Antipyretics – used to treat fever; include acetaminophen and aspirin; work by
blocking formation of pyrogens; permits hypothalamus to return to normal set point
REGULATION OF FEEDING

Hypothalamus also regulates feeding
 Stimulation of certain hypothalamic nuclei induces hunger and feeding behaviors;
indirectly preserves homeostasis of glucose
 Thought to be related to secretion of neurotransmitters called orexins
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
33
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
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 infants require about 17 hours
per night
SLEEP AND WAKEFULNESS

Sleep (continued):
 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
SLEEP AND WAKEFULNESS

Sleep occurs in following sequence of events (Figure 12.34):
 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
 Ventrolateral preoptic nucleus decreases activity of reticular formation
SLEEP AND WAKEFULNESS

Sleep (continued):
 Decreased activity of reticular formation “disconnects” 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
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
34

Waves differ in height (amplitude) and speed at which they are generated
(frequency)
SLEEP AND WAKEFULNESS

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)
SLEEP AND WAKEFULNESS

Brain Waves and Stages of Sleep (continued):
 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
STATES OF ALTERED CONSCIOUSNESS MIMICKING SLEEP

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
STATES OF ALTERED CONSCIOUSNESS MIMICKING SLEEP

Altered consciousness can indicate serious problems with brain function; examples
include (continued):
 Coma (continued):
o EEG demonstrates slow, fixed pattern with no observable sleep/wake cycles
o Brainstem reflexes remain intact; certain patients exhibit involuntary
movements
o May result from head trauma, certain drugs, disturbances in acid-base
homeostasis and various neurological conditions
STATES OF ALTERED CONSCIOUSNESS MIMICKING SLEEP

Altered consciousness can indicate serious problems with brain function; examples
include (continued):
 Persistent vegetative state – some patients move from coma state to condition
where they are awake but unaware because of damage to cerebral cortex; also
lack voluntary movement
35
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
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
MODULE 12.8 HIGHER MENTAL FUNCTIONS
COGNITION AND L ANGUAGE

Cognition – collective term for diverse group of tasks; 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
COGNITION AND L ANGUAGE

Localization of Cognitive Function – following areas 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
COGNITION AND L ANGUAGE

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
COGNITION AND L ANGUAGE

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
36

amount of brain space
Following functions appear to be lateralized although this is not an absolute (next
slide)
COGNITION AND L ANGUAGE

Cerebral lateralization (continued):
 Following functions appear to be lateralized although this is not an absolute
(continued):
o Emotional functions – left frontal cortex is mostly responsible for “positive”
emotions while right cortex for “negative” emotions
o Attention is lateralized to right parietal cortex while facial recognition is
lateralized in right temporal cortex
o Language-related recognition and ability to identify an object with its proper
name are lateralized in left temporal cortex
DEMENTIA


Patients with dementia exhibit a progressive loss of 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
DEMENTIA

Common (most to least) forms of dementia include:
 Alzheimer’s disease (AD)
o 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
o 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
DEMENTIA

Common (most to least) forms of dementia include (continued):
 Vascular dementia
o Group of diseases; share common feature of disruption in blood flow to parts
of brain, particularly cerebral cortex
o Signs and symptoms are highly variable because of range of brain regions
affected
o Significant overlap with AD; patients often have both forms; known as mixed
dementia
DEMENTIA

Common (most to least) forms of dementia include (continued):
37

Lewy body dementia
o Cytoplasmic inclusions (Lewy bodies) in neurons of certain brain parts
o Fluctuation in cognitive functions, impaired memory formation,
hallucinations, delusions, sleep disorders, and motor features of Parkinson’s
disease
DEMENTIA

Common (most to least) forms of dementia include (continued):
 Pick’s disease
o Cerebral cortex of frontal and temporal lobes progressively degenerates
o Results in severe atrophy due to loss of neurons with excess neuroglia
o Unusual, in that younger population affected (age 55–65)
o Patients deteriorate rapidly; dramatic personality changes and behavioral
problems common because of prefrontal cortex involvement
COGNITION AND L ANGUAGE

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 L ANGUAGE

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
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 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
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
38

Nondeclarative examples – how to enter phone number on a phone, how to move
your mouth to speak, and how to read this chapter
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
LEARNING AND MEMORY


Process of converting immediate or working memory 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
LEARNING AND MEMORY

Long-term potentiation (LTP) – mechanism by which hippocampal neurons encode
long-term declarative memories, seems to involve an increase in synaptic activity
between associated neurons; example of Cell-Cell 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
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
LEARNING AND MEMORY

Emotion – complex combination of three separate phenomena:
 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
LEARNING AND MEMORY

Emotion (continued):
 “Feelings” – highly subjective; most complex; integrated with sensory and/or
cognitive stimuli
o Feeling sad when remembering a lost pet or feeling tense when watching a
suspenseful movie
39
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
40