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Neural Organization and Simple Reflexes

Neural Organization and Simple Reflexes. Anterior Motor Neurons. Alpha motor neurons give rise to large type A alpha fibers (~14 microns). stimulation can excite 3 - 100 extrafusal muscle fibers collectively called a motor unit Gamma motor neurons

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Neural Organization and Simple Reflexes

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  1. Neural Organization and Simple Reflexes

  2. Anterior Motor Neurons • Alpha motor neurons • give rise to large type A alpha fibers (~14 microns). • stimulation can excite 3 - 100 extrafusal muscle fibers collectively called a motor unit • Gamma motor neurons • give rise to smaller type A gamma fibers (~5 microns) • stimulation excites intrafusal fibers, a special type of sensory receptor

  3. The Muscle Spindle • - sense muscle length and change in length Figure 54-2; Guyton and Hall

  4. Physiologic Function of the Muscle Spindle • Compares length between the intrafusal and extrafusal muscle fiber. • Opposes a change in length of the muscle. • When the muscle is stretched the spindle returns it to its original length. • Leads to the stretch reflex.

  5. Components of the Stretch Reflex

  6. The Patellar Reflex

  7. The Withdrawal Reflexes • A painful stimulus causes the limb to automatically withdraw from the stimulus. • Neural pathways for reflex: • nociceptor activation transmitted to the spinal cord • synapses with pool of interneurons that diverge the to the muscles for withdrawal, inhibit antagonist muscles, and activate reverberating circuits to prolong muscle contraction • duration of the afterdischarge depends on strength of the stimulus

  8. Components of a Flexor Withdrawal Reflex

  9. Crossed Extensor Reflex • Painful stimulus elicits a flexor reflex in affected limb and an extensor reflex in the opposite limb. • Extensor reflex begins 0.2 - 0.5 seconds after the painful stimulus. • Serves to push body away from the stimulus, also to shift weight to the opposite limb.

  10. The Flexor Withdrawal/Crossed Extensor Reflexes

  11. Reflexes that Cause Muscle Spasm • Pain signals can cause reflex activation and spasm of local muscles. • Inflammation of peritoneum can cause abdominal muscle spasm. • Muscle cramps caused by painful stimulus in muscle: • can be due to cold, ischemia, of overactivity • reflex contraction increases painful stimulus and causes more muscle contraction

  12. Origins of the Cranial Nerves PLAY

  13. Origins of the Cranial Nerves PLAY

  14. The Olfactory Nerve PLAY

  15. Cranial Nerves Controlling the Extra-ocular Muscles PLAY Figure 14.23

  16. The Trigeminal Nerve PLAY

  17. The Facial Nerve PLAY

  18. The Vestibulocochlear Nerve PLAY

  19. The Glossopharyngeal Nerve PLAY

  20. The Vagus Nerve PLAY

  21. The Accessory and HypoglossalNerve PLAY

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