The brain is composed of neurons that transmit signals through the nervous system. There are two main parts: the central nervous system (CNS) and the peripheral nervous system (PNS). The CNS contains the brain and spinal cord. The brain is divided into different lobes and structures that each have unique functions, such as controlling movement, senses, thinking, emotions, homeostasis and more. The PNS connects to the CNS and contains nerves that link to the rest of the body. Together the brain and nervous system allow for processing information and controlling bodily functions.

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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