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7/08/12 The Brain (& CNS)!
Lecture 12a
BIOL241
Final Exam (Exam 4)!
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Chapters 11 – 15*
100 points
Multiple choice, T/F, matching, fill in
Short answer, essays (2)*
Labeling (brain [including functions],
cranial nerves, spinal cord)
1 7/08/12 Outline
•  Overview of the human brain
•  Tour through the brain – structures and
functions
•  Cerebral hemispheres and higher mental
functions
•  Meninges
•  Ventricles and CSF
•  Brain disorders
The Human Brain
•  Composed of wrinkled, pinkish gray tissue
•  Surface anatomy includes cerebral
hemispheres, cerebellum, and brain stem
•  Ranges from 750 cc to 2100 cc
•  Contains almost 98% of the body’s neural
tissue
•  Average weight, adult: 1300 – 1400 gm (~3 lb)
•  1010 to 1011 neurons
•  Trillions of connections
•  men = larger
•  Women = better connected
2 7/08/12 Major Regions and Landmarks
Figure 14–1
Embryology of the Brain
Table 14-1
3 7/08/12 Regions of the Adult Brain
•  Telencephalon (cerebrum) – cortex, white
matter, and basal nuclei
•  Diencephalon – thalamus, hypothalamus,
and epithalamus
•  Mesencephalon –midbrain (brain stem)
•  Metencephalon – pons (brain stem),
cerebellum
•  Myelencephalon – medulla oblongata
(brain stem)
Basic Pattern of the Central Nervous
System
•  Spinal Cord
–  Central cavity surrounded
by a gray matter core
–  External to which is white
matter composed of
myelinated fiber tracts
•  Brain
–  Similar to spinal cord but
with additional areas of
gray matter
–  Cerebellum has gray matter
in nuclei
–  Cerebrum has nuclei and
additional gray matter in the
cortex
Figure 12.4 4 7/08/12 Some terms
•  nucleus: collection of neuron cell
bodies in the CNS
•  tract: collection of axons in the CNS
•  ganglia: collection of neuron cell
bodies in the PNS
•  nerve: collection of axons in the PNS
–  Cranial nerves
–  Spinal nerves
Tour of the brain
•  From caudal/inferior to rostral/superior
5 7/08/12 The Brain Stem
•  Processes information between spinal cord and
cerebrum or cerebellum
•  Controls automatic behaviors necessary for
survival
•  Associated with 10 of the 12 pairs of cranial
nerves (covered later)
•  Includes:
–  mesencephalon (midbrain)
–  pons
–  medulla oblongata
–  Note: some consider the diencephalon part of the
brain stem as well
Brain Stem
Figure 12.15a 6 7/08/12 Anatomy:
Brain stem
Most cranial
nerves are
located in the
brain stem
Brain Stem
Figure 12.15b 7 7/08/12 Posterior view
Medulla Oblongata
•  Most inferior part of brain, connects brain to
spinal cord
•  Relays information
•  Pyramids – two longitudinal ridges formed by
corticospinal tracts
•  Regulates autonomic functions:
–  regulates arousal, heart rate, blood pressure, pace
for respiration and digestion
•  Cranial nerves IX, X, XI, XII come off or enter
8 7/08/12 Medulla Oblongata
Figure 12.16c Medulla Oblongata
9 7/08/12 Medulla Nuclei
•  Cardiovascular control center – adjusts
force and rate of heart contraction
•  Respiratory centers – control rate and
depth of breathing
•  Additional centers – regulate vomiting,
hiccupping, swallowing, coughing, and
sneezing
Pons
10 7/08/12 Pons
•  Involved in somatic and visceral motor control
•  Contain the nuclei for cranial nerves V, VI, VII,
VIII
•  Contains nuclei of the reticular formation
•  Control of respiration that modifies the info from
the medulla
•  Nuclei and tracts passing through to the
cerebellum (motor and somatosensory info)
•  Nuclei and tracts to other portions of the CNS
(just passing through)
Cerebellum
11 7/08/12 Cerebellum
•  “little brain”
•  Second largest part of brain (~10% mass)
•  Provides precise timing and appropriate patterns of
skeletal muscle contraction to coordinate repetitive
body movements and help learning complex motor
behaviors
•  Adjusts the postural muscles of the body, controls
balance and equilibrium
•  Has 2 hemispheres, covered with cerebellar cortex
•  Recognizes and predicts sequences of events
•  Cerebellar activity occurs subconsciously (as does all
processing that occurs outside the cerebral cortex)
Cerebellum – side (or) view
12 7/08/12 Cerebellum
•  Cerebellum receives impulses of the intent to
initiate voluntary muscle contraction
•  Monitors all proprioceptive info and visual info
about body position
•  Cerebellar cortex calculates the best way to
perform a movement
•  Programs and fine tunes movements by
detecting mismatches in intended and actual
movements
-- when learning to ride a bike, throw a curve ball
or tie your shoe, cerebellum activity is high.
When they become automatic, cerebellum is no
longer involved
Mesencephalon
13 7/08/12 Mesencephalon •  Also called midbrain
•  Processes sight, sound, and associated
reflexes
•  Maintains consciousness
•  Cranial nerve nuclei III and IV
•  2 basic divisions
–  tectum (roof)
–  tegmentum
Mesencephalon
•  Process of visual and auditory sensations
–  corpora quadrigemina (in tectum) = superior colliculi (visual
reflex) and inferior colliculi (auditory reflex)
•  Substantia nigra (in tegmentum)
–  Neurons inhibit activity of cerebral nuclei by releasing
dopamine
–  If damaged, results in less dopamine released and muscle
tone increases: muscle rigidity, difficulty initiating movement
= Parkinson’s Disease
•  Reticular formation: maintain consciousness
14 7/08/12 Midbrain Nuclei
Figure 12.16a Mesencephalon
15 7/08/12 Diencephalon
Figure 12.12 Diencephalon
•  Located under
cerebrum and
cerebellum
•  Links cerebrum
with brain stem
•  Integrates sensory
information and
motor commands
•  Cranial nerve II
16 7/08/12 Diencephalon
•  Pineal Gland
– Secretes hormone melatonin
•  Thalamus:
– relays and processes sensory information
•  Hypothalamus:
– hormone production
– emotion
– autonomic function
Diencephalon: Thalamus
•  Paired, egg-shaped
masses connected
at the midline by the
intermediate mass
•  Nuclei project to
and receive fibers
from the cerebral
cortex
Figure 14–9
17 7/08/12 Thalamus
•  Sensory Relay station
•  All sensory that is projected to the cerebral
cortex stops here first except smell
•  Filters ascending sensory information for
primary sensory cortex
•  Relays information between basal nuclei
and cerebral cortex
•  Mediates sensation, some motor activities,
cortical arousal (thus learning, and
memory)
Diencephalon: Hypothalamus
•  Lies below
thalamus
Figure 14–10a
18 7/08/12 Hypothalamus
•  Captain of the Autonomic nervous system,
master overseer of homeostasis
–  Emotions and behavior: mediates perception of
pleasure, fear, and rage
–  Regulation of body temperature, blood pressure,
digestive tract motility, rate and depth of breathing,
and many other visceral activities
–  Food intake (drives)
–  Water balance/thirst
–  Day/night rhythms
–  Endocrine functions- ADH and oxytocin
Structures of the Hypothalamus
•  Mamillary bodies:
–  Relay station for olfactory information
–  control reflex eating movements
19 7/08/12 Pituitary Gland
•  Major endocrine gland, controls all
others
•  Connected to hypothalamus via
infundibulum (stalk)
•  Interfaces nervous and endocrine
systems because it is controlled by
the hypothalamus
Telencephalon
•  Basal nuclei
•  Cerebrum
20 7/08/12 The Basal Nuclei (Ganglia)
Figure 14–14b, c
Basal Nuclei
•  Also called basal ganglia
•  Masses of gray matter found deep within the
cortical white matter
•  The corpus striatum is composed of three
parts
–  Caudate nucleus
–  Lentiform nucleus = putamen and the globus
pallidus
–  Fibers of internal capsule running between and
through caudate and lentiform nuclei
•  Direct subconscious activities
21 7/08/12 Functions of Basal Nuclei
•  Are involved with:
–  Subconscious control of skeletal muscle tone
–  Regulate attention and cognition
–  Regulate intensity of slow or stereotyped
movements (walking, lifting)
–  Inhibit antagonistic and unnecessary
movement
–  Subconscious habit learning
–  May store simple movement patterns
Basal Nuclei
Figure 12.11b 22 7/08/12 Cerebrum •  Largest part of brain (make up 83% of its
mass)
•  Controls higher mental functions including
all conscious thoughts and experience
including all intellectual functions (more
about this later)
•  Processes somatic sensory and motor
information
•  Divided into left and right cerebral
hemispheres
•  Surface layer of gray matter (cerebral cortex)
(Cerebral) Cortex
•  Gray matter covering cerebral
hemispheres
•  Accounts for 40% of the mass of the
brain
•  Folded surface increases surface area
•  Elevated ridges = gyri (gyrus)
•  Shallow depressions = sulci (sulcus)
•  Deep grooves = fissures
23 7/08/12 Cerebral Gray and White Matter
•  Gray matter:
–  Cell bodies
–  Found in cerebral cortex and basal nuclei
•  White matter:
–  Fiber tracts (axons)
–  Deep to cerebral cortex
–  Surrounding basal nuclei
White Matter of the Cerebrum
•  Myelinated fibers (axons)
–  Association fibers:
•  arcuate: local
•  longitudinal: within one
hemisphere
–  Commissural: between
hemispheres
–  Projection: link
cerebral cortex with
rest of CNS
Figure 14–13
24 7/08/12 Examples
•  Projection Fibers: Internal capsule
–  all ascending and descending projection
fibers to and from cerebral cortex, passes
though basal nuclei
•  Commissural fibers: corpus callosum
–  Connect the two cerebral hemispheres
Fiber Tracts in White Matter
Figure 12.10b 25 7/08/12 Limbic System
Figure 12.18 The Limbic System
•  One of two networks of neurons working
together and spanning wide areas of the brain –
the other is the consciousness regulating
reticular formation (where?)
•  A of the medial functional grouping of the medial
cerebral hemispheres and diencephalon that:
–  establishes emotional states and drives
–  links conscious functions of cerebral cortex with
autonomic functions of brain stem
–  Allows us to react emotionally to conscious
understanding and to be aware of emotions
–  facilitates memory storage and retrieval
26 7/08/12 The Limbic System
Figure 14–11a
Components of the Limbic System
•  Amygdala
–  deals with anger, danger, and fear responses,
along with emotional smell memories
•  Limbic lobe of cerebral hemisphere:
–  Cingulate gyrus: plays a role in expressing
emotions via gestures, and resolves mental
conflict (emotion)
–  Hippocampus: convert new information into
long-term memories (patient H.M.?)
27 7/08/12 Components of the
Limbic System Continued
•  Fornix:
–  tract of white matter that connects
hippocampus with hypothalamus
•  Diencepalic structures:
–  Portions of thalamus, hypothalamus
Reticular Formation
Sends
impulses to
the cerebral
cortex to
keep it
conscious
and alert
Figure 12.19 28 7/08/12 Higher Level Functions of
Cerebral Hemispheres
The Cerebral Cortex 4 Lobes:
Frontal
Parietal
Temporal
Occipital
Figure 14–12b
29 7/08/12 Cerebral cortex
•  It enables sensation, communication,
memory, understanding, and voluntary
movements
•  Temporal lobe: memory, hearing
•  Frontal lobe: executive function, language
•  Parietal lobe: sense of self
•  Occipital lobe: vision
Cerebral Cortex landmarks
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Lateral sulcus
Longitudinal fissure
Central sulcus
Precentral gyrus (primary motor)
Postcentral gyrus (primary sensory)
Association areas are for integrating
information
30 7/08/12 Motor and Sensory Areas
of the Cortex
•  Central sulcus separates motor and
sensory areas
Figure 14–15a
Functional Areas of the Cerebral
Cortex
•  The three types of functional areas are:
–  Motor areas – control voluntary movement
–  Sensory areas – conscious awareness of
sensation
–  Association areas – integrate diverse
information
31 7/08/12 Functional Areas of the Cerebral Cortex
Figure 12.8a Functional Areas of the Cerebral Cortex Figure 12.8b 32 7/08/12 Motor Areas
•  Precentral gyrus of frontal lobe:
–  directs voluntary movements
•  Primary motor cortex:
–  is the surface of precentral gyrus
Sensory Areas
•  Postcentral gyrus of parietal lobe:
–  receives somatic sensory information
(touch, pressure, pain, vibration, taste, and
temperature)
•  Primary sensory cortex:
–  surface of postcentral gyrus
33 7/08/12 Association Areas
•  Any brain region that receives input from
more than one sensory modality
•  aka “integrative areas” or higher level
association areas
•  Relative abundance determines intellectual
capacity
•  Include:
–  Prefrontal cortex
–  Language areas
–  General (common) interpretation area
–  Visceral association area
Functional Principles
of the Cerebral hemispheres
1.  Each cerebral hemisphere receives sensory
information from, and sends motor
commands to, the opposite side of body
2.  The 2 hemispheres have somewhat different
functions although their structures are alike
3.  Correspondence between a specific
function and a specific region of cerebral
cortex is not precise
4.  No functional area acts alone; conscious
behavior involves the entire cortex
34 7/08/12 Higher level: Prefrontal Cortex
•  Most complicated region, coordinates
info from all other association areas
•  Important in intellect, planning,
reasoning, mood, abstract ideas,
judgement, conscience, and accuratley
predicting consequences
•  Phineas Gage?
Phineas Gage
35 7/08/12 Phineas Gage
•  In 1848 in Vermont, had a 3.5-foot-long,
13 lb. metal rod blown into his skull,
through his brain, and out of the top of his
head. Gage survived. In fact, he never
even lost consciousness.
•  Friends reported a complete change in his
personality after the incident. He lost all
impulse control.
“Right Brain – Left Brain”
36 7/08/12 Hemispheric Lateralization
•  Functional differences between left and
right hemispheres
•  In most people, left hemisphere
(dominant hemisphere) controls:
–  reading, writing, and math, decisionmaking, logic, speech and language
(usually)
•  Right cerebral hemisphere relates to:
–  recognition (faces, voice inflections), affect,
visual/spatial reasoning, emotion, artistic
skills
Brain Waves
•  Alpha waves – regular and rhythmic, lowamplitude, slow, synchronous waves
indicating an “idling” brain (drifting off)
•  Beta waves – rhythmic, more irregular
waves occurring during the awake and
mentally alert state
•  Theta waves – more irregular than alpha
waves; common in children but abnormal
in adults
•  Delta waves – high-amplitude waves seen
in deep sleep and when reticular activating
system is damped
37 7/08/12 Types of Brain Waves
Figure 12.20b Ventricles of the brain
38 7/08/12 Ventricles
•  Lined by ependymal cells which help to
form the choroid plexus
•  There are two lateral ventricles in the
cerebral hemispheres
•  Third ventricle is located in the
diencephalon
•  Fourth ventricle is located between the
pons and the cerebellum
Cranial
meninges
39 7/08/12 Cranial meninges
•  Dura mater consists of an outer
(endosteal layer) and an inner (meningeal
layer)
–  In between the layers find the dural sinus
•  Arachnoid membrane covers the surface
of the brain, have a subarachnoid space
•  Pia mater is anchored to the brain by
astrocytes, wraps brain tightly like saran
wrap
Inter-Layer Spaces –
just like in the brain
•  Subdural space:
–  between arachnoid mater and dura mater
•  Subarachnoid space:
–  between arachnoid mater and pia mater
–  contains collagen/elastin fiber network that’s
“spiderweb-like” (arachnoid trabeculae)
–  filled with cerebrospinal fluid (CSF)
àSubdural, subarachanoid spaces are
frequent sites of intracranial bleeding
40 7/08/12 Cerebrospinal Fluid (CSF)
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• 
• 
Surrounds all exposed surfaces of CNS
Cushions, supports, and transports
Interchanges with interstitial fluid of brain
Like plasma or interstitial fluid elsewhere
except much more pure
•  Arachnoid villi protrude superiorly into
dural sinus and permit CSF to be
absorbed into venous blood
Choroid Plexuses
•  Clusters of capillaries
lined by ependymal
cells that form tissue
fluid filters, which
hang from the roof of
each ventricle
•  Have ion pumps that
allow them to alter ion
concentrations of the
CSF
•  Help cleanse CSF by
removing wastes 41 7/08/12 CSF flow: through
ventricles, to
arachnoid space, to
dural sinuses (back
to circulation)
Blood Supply to the Brain
•  Supplies nutrients and oxygen to brain
•  Delivered by internal carotid arteries
and vertebral arteries
•  Removed from dural sinuses by
internal jugular veins
42 7/08/12 Blood–Brain Barrier
•  Isolates CNS neural tissue from general
circulation
•  Formed by network of tight junctions
between endothelial cells of CNS
capillaries and by feet of astrocyte
processes
•  Astrocytes control blood–brain barrier by
releasing chemicals that control
permeability of endothelium
Blood–Brain Barrier
•  Lipid–soluble compounds (O2, CO2),
steroids, and prostaglandins diffuse
into interstitial fluid of brain and spinal
cord
•  Other things have to be transported in
43 7/08/12 Cerebrovascular Disease
•  Disorders interfere with blood circulation to
brain
•  Stroke or cerebrovascular accident (CVA):
–  shuts off blood to portion of brain
–  neurons die
•  Tissue plasminogen activator (TPA) is the
only approved treatment for stroke (except
aspirin)
•  Transient Ischemic Attach (TIA)
Degenerative Brain Disorders
•  Alzheimer’s disease – a progressive
degenerative disease of the brain that results
in dementia (usually frontotemporal)
•  Parkinson’s disease – degeneration of the
dopamine-releasing neurons of the substantia
nigra
•  Huntington’s disease – a fatal hereditary
disorder caused by accumulation of the
protein huntingtin that leads to degeneration
of the basal nuclei
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