Pns blog

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Pns blog

  1. 1. Peripheral Nervous System
  2. 2. The Basics: <ul><li>Works together with CNS </li></ul><ul><li>Provides a flow path to/from brain </li></ul><ul><li>Links CNS to and from the real world </li></ul><ul><li>Can classify sensory receptors by stimulus type or by location </li></ul>
  3. 3. PNS Divisions <ul><li>Sensory division - input; travels to CNS </li></ul><ul><li>Motor division - output; travels away from CNS </li></ul><ul><li>Motor subdivisions: </li></ul><ul><li>Somatic nervous system </li></ul><ul><li>Autonomic nervous system </li></ul>
  4. 4. Somatic Nervous System <ul><li>Also called the voluntary nervous system </li></ul><ul><li>It allows us to consciously control our skeletal muscles….how? </li></ul><ul><li>By providing a pathway for those signals to reach the neuromuscular junction from the CNS </li></ul><ul><li>Major neurotransmitter: acetylcholine </li></ul>
  5. 5. Autonomic Nervous System <ul><li>Innervates cardiac & smooth muscle, and glands </li></ul><ul><li>Major neurotransmitters: acetylcholine, norepinephrine </li></ul><ul><li>Broken into two subdivisions; dual innervation! </li></ul><ul><li>Both subdivisions serve same visceral organs…. </li></ul><ul><li>But, cause opposite effect! </li></ul><ul><li>One division stimulates, the other inhibits </li></ul>
  6. 6. Sympathetic Division <ul><li>Also called the “fight or flight” system </li></ul><ul><li>Stressful situations cause: </li></ul><ul><li>Deep breathing, cold/sweaty skin, dilated pupils, and electrical resistance of skin (galvanic skin resistance) </li></ul><ul><li>GSR - used in lie detector tests </li></ul><ul><li>Constricts blood vessels, autonomic activity decreased </li></ul><ul><li>Provides optimal conditions to a response from a threat to homeostasis </li></ul>
  7. 7. Parasympathetic Division <ul><li>Most active in non-stressful situations </li></ul><ul><li>Called “resting & digesting” system </li></ul><ul><li>Tries to keep body energy use as low as possible </li></ul><ul><li>This is why we rest after a heavy meal ….. </li></ul><ul><li>… .digestion not interfered with by sympathetic activity </li></ul><ul><li>Nerve fibers emerge from brain and sacral areas </li></ul>
  8. 8. Reflex Activity <ul><li>Reflex = a rapid, predictable motor response to a stimulus </li></ul><ul><li>Involuntary & unlearned </li></ul><ul><li>Involves “reflex arcs” </li></ul><ul><li>Classified as somatic reflexes and autonomic (visceral) reflexes </li></ul><ul><li>Same pathway as feedback mechanism - but integration occurs in spinal cord </li></ul>
  9. 9. Reflex Types/Examples <ul><li>Flexor (withdrawal) reflex - response when you prick your finger with a needle </li></ul><ul><li>Crossed extensor reflex - e.g. when someone unexpectedly grabs your arm or you step barefoot on broken glass. Important in balance!! </li></ul><ul><li>Superficial reflex - caused by gentle cutaneous (skin) stimulation - spider or tick crawling on your skin </li></ul><ul><li>Plantar reflex - caused by pushing a blunt object downward along the sole of the foot (toes will curl) </li></ul>
  10. 10. Electrical Brain Activity <ul><li>Measured by an electroencephalogram (EEG) </li></ul><ul><li>Unique to every individual </li></ul><ul><li>Each of us has brain wave pattern as unique as a fingerprint </li></ul><ul><li>But ….can group into four frequency classes: </li></ul>
  11. 11. Alpha Waves <ul><li>Low-amplitude </li></ul><ul><li>Slow </li></ul><ul><li>Synchronous </li></ul><ul><li>8-13 Hz </li></ul><ul><li>Indicate a calm, relaxed state of wakefulness </li></ul>
  12. 12. Beta Waves <ul><li>Rhythmic </li></ul><ul><li>More irregular than alpha waves </li></ul><ul><li>Higher frequency; 14-25 Hz </li></ul><ul><li>Occur when awake & mentally alert (concentrating on things) </li></ul>
  13. 13. Theta Waves <ul><li>Irregular waves </li></ul><ul><li>Frequency of 4-7 Hz </li></ul><ul><li>Considered abnormal in people who are awake </li></ul>
  14. 14. Sleep <ul><li>Significance not really understood </li></ul><ul><li>Sleep requirements: </li></ul><ul><li>16 hrs/day for infants </li></ul><ul><li>7 hrs/day for adults </li></ul><ul><li>Possible hypotheses: </li></ul><ul><li>Recharge mechanism </li></ul><ul><li>Dream to forget </li></ul><ul><li>Other ….??? </li></ul><ul><li>There are different stages of sleep </li></ul>
  15. 15. NREM Stages <ul><li>Stage 1 - eyes closed, relaxed. Drifting sensation occurs. Alpha waves. </li></ul><ul><li>Stage 2 - EEG becomes more irregular, arousal more difficult </li></ul><ul><li>Stage 3 - Deeper sleep, alpha & delta waves occur. Relaxed skeletal muscles. Dreaming. 20 minutes after stage 1 </li></ul><ul><li>Stage 4 - slow wave sleep; sleepwalking & bedwetting occur here. Vital signs at lowest levels. </li></ul>
  16. 16. REM Sleep <ul><li>Very irregular brain waves </li></ul><ul><li>Eyes move rapidly </li></ul><ul><li>Starts approx. 90 minutes after sleep begins </li></ul><ul><li>Often called “paradoxical” sleep. (EEG pattern looks like when we’re awake) </li></ul><ul><li>Most dreaming occurs here </li></ul>
  17. 17. Memory <ul><li>Memory storage occurs in stages </li></ul><ul><li>Short-term memory (STM) and Long-term memory (LTM) </li></ul><ul><li>STM - limited to 6-7 chunks of information </li></ul><ul><li>Transfer from STM to LTM depends on: </li></ul><ul><li>Emotional state </li></ul><ul><li>Rehearsal </li></ul><ul><li>Automatic memory </li></ul><ul><li>Memory must consolidate </li></ul>
  18. 18. Memory Categories <ul><li>Fact (declarative) memory </li></ul><ul><li>Learning names, faces, words, dates, etc </li></ul><ul><li>Skill (procedural) memory </li></ul><ul><li>Less conscious learning </li></ul><ul><li>Acquired only through practice </li></ul><ul><li>Best remembered by doing </li></ul>

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