HOW THE BRAIN WORKS

DR. JAMES M. ALO

I. Anatomy/Physiology

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

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

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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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