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 across
junction bet. nerve cells (synapse) }chemical
interaction
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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
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
 Postcentralgyrus – 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
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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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