1. HOW THE BRAIN
WORKS
DR. JAMES M. ALO

2. I. Anatomy/Physiology
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A. Neuron- highly specialized for the processing
and transmission of cellular signals
1. Basic component of the nervous sy.
2. Composed of cell body, axon & dendrites
a. Cell body = center of metabolism
b. Axon =long fibers > conduct impulses away from the
cell body; usually 1 axon for each cell body
c. Dendrites = short, unsheathed fibers> receive nerve
impulses> transmit to cell body
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3. Myelin sheath – covering that protects nerve fiber>
facilitates> speed of impulse conductor
a. Axon & dendrite – may/may not have myelin
sheath
b. Most axons leaving the CNS – heavily
myelinated w/ schwann cells
c. Gaps in myelin sheath – termed Nodes of
Ranvier
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4. Primary fxn – transmission of nerve
impulses
a. Afferent (sensory) n. – transmit impulses
from peripheral receptors } CNS
b. Efferent (motor) n. – conduct impulses
from CNS
c. Action potentials travel along axons} end
of nerve fiber }impulse is transmitted
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across junction bet. nerve cells (synapse)

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5. Neuroglia – glial cells
a. Provide support,
b. Nourishment and
c. Protection for neurons
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B. PNS } contains
cranial nerves,
spinal nerves,
autonomic nervous
system(unconscious
reflexes),
sympathetic division
(accelerates
activity), &
parasympathetic
division(slows body drjAlo
processes).

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C. CNS contains:
1. Cerebrum – divided into: left right hemisphere}
longitudinal fissure
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a. Frontal lobes
 Precentral gyrus – contralateral movement; face, arm,
leg, trunk
 Broca’s area – dominant hemisphere } respon.>
formation of words
 Supplementary motor area – contralateral head & eye
turning
 Prefrontal area- personality, initiative
 Paracentral lobule- contralateral inhibition of bladder &
bowel
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b. Parietal lobes
 Postcentral gyrus – body sensations; temp, touch,
pressure, pain }from opposite side of the body
 Dominant parietal lobe- wernickes’ speech area,
auditory & visual aspects> comprehensions are
integrated
 Responsible for skills { handle numbers & calculations
 Nondominant parietal lobe- concept of body
image & awareness of external envi{ ability to
construct shapes
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c. Occipital lobes – visual center;
comprehension of written word
d. Temporal lobes
 Dominant hearing of language; taste, smell
 Memory
 Wernicke’s speech area – recognition of language
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2. Basal ganglia – reg & integr skeletal voluntary &
autonomic motor activity originating in cerebral
cortex
3. Diencephalon – connects the cerebrum & brain
stem; contains several small structures, the most
important of w/c are the thalamus & hypothalamus
a. Thalamus – relay station for discrimination of
sensation }received from periphery>several nuclei in
the thalamus, each w/ specific fxns} such as:
integration of sensory stimuli necessary for abstract
thinking & reasoning, vision, hearing; relay station for
fibers going to limbic system drjAlo

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 Hypothalamus- responsible for maintaining
momeostasis} thru the secretion of hormones &
central control of ANS
 Controls vital fxn: water balance, BP, sleep, appetite,
temp
 Affects some emotional responses ] pleasure/fear
 Control center for pituitary fxn
 Affects both divisions of the ANS
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c. Limbic system –responsible for controlling
various functions in the body. Structures of this
system include the hippocampus,
hypothalamus, and thalamus
 Fig.
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4. Brain stem- contains; midbrain, pons &
medulla oblangata, extending from the
cerebral hemispheres to the foramen magnum
@ the base of the skull
a. Contains nuclei- 5,6,7,8th Cnerves & ascending
sensory & descending motor tracts
b. Contains vital center- respiratory, vasomotor &
cardiac fxn
c. Reticular formation – relays sensory of info;
controls vasomotor/respiratory activity
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5. Ventricular system & CSF – supports &
cushions CNS
 Removes metabolic wastes
 Compensatory mechanisms for
ICVolume/pressure
 Produces 55 cc/d of CSF; 130-150cc amt ave in
sy
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6. Cranial meninges
 Dura mater – dense, fibrous, outermost layer serves
as periosteum for Cnerves
 Arachnoid mater
 Delicate, avascular membrane lying under dura
 Surrounds brain loosely
 Subarachnoid space contains; CSF, arteries & veins
 Contains arachnoid granulations that enable CSF } pass
from subarachnoid space>venous system
 Pia mater
 Most delicate inner meningeal layer
 Barrier system
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7. Cerebellum – control of: muscle motion,
balance, coordination; trunk mobility &
equilibrium
 Spinal cord – communications link bet CNS &
PNS
 Ascending pathways ] transmit
 Sensory information
 Descending pathways] relay
 Motor instrtuctions
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Thank You.
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