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How the brain works


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How the brain works

  2. 2. I. Anatomy/Physiology2 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 drjAlo
  3. 3. 3 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 drjAlo
  4. 4. 4 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 drjAlo
  5. 5. 5 5. Neuroglia – glial cells a. Provide support, b. Nourishment and c. Protection for neurons drjAlo
  6. 6. 6 B. PNS } contains cranial nerves, spinal nerves, autonomic nervous system(unconscious reflexes), sympathetic division (accelerates activity), & parasympathetic division(slows body processes). drjAlo
  7. 7. 7 C. CNS contains: 1. Cerebrum – divided into: left right hemisphere} longitudinal fissure drjAlo
  8. 8. 8 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 drjAlo
  9. 9. 9 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 drjAlo
  10. 10. 10 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 drjAlo
  11. 11. 11 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
  12. 12. 12  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 drjAlo
  13. 13. 13 c. Limbic system –responsible for controlling various functions in the body. Structures of this system include the hippocampus, hypothalamus, and thalamus  Fig. drjAlo
  14. 14. 14 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 drjAlo
  15. 15. 15 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 drjAlo
  16. 16. 16 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 drjAlo
  17. 17. 17 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 drjAlo
  18. 18. 18 Thank You. drjAlo