anatomy 11 - 10/29/08 REFLEXES reflexes are rapid,...

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10/29/08 - REFLEXES o reflexes are rapid, automatic, involuntary reactions of muscles or glands to a stimulus o intended simply to move the affected part of your body away from the stimulus (step on something, you jerk your foot away, and then look at what it is/ decide what to do about it). Purpose is to prevent your body from being injured by stimulus. - Fig 16.12 reflex arc o Reflex arc – 99% of impulses o Components: 1- stimulus 2- one or more sensory neurons 3- one or more interneurons 4- one or more motor neurons 5- necessary muscles or glands required to remove yourself from stimulus o Brain typically not involved- just your spinal cord - Fig 16.13 monosynaptic reflex o Only one synapse- between sensory neuron and motor neuron o Example: a knee jerk Strikes you below the patella, on patellar ligament(connects patella and tibia) (made of collagen fibers- no elasticity), basically distorts/bends it, no elasticity so it has to pull something, pulls patella because it is the smaller. Patella connected to another tendon (also made of collagen, no elasticity), pulls on the muscle, (which does have elasticity), muscle will stretch, inside the muscle are proprioreceptors- receptors that are right in the muscle fibers, they sense any movement, which depolarizes proprioreceptors, which stimulates a sensory neuron, sensory neuron sends an impulse into the spinal cord. Will enter the spinal cord at your midsection. Why does it only have to synapse with one motor neuron? That’s all it takes to tighten up the muscle When mallet hits you, you felt the impact of the mallet on your skin, that is NOT the sensory impulse that caused your leg to jerk, that simply told
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This note was uploaded on 03/18/2009 for the course BS 240 taught by Professor Zink during the Spring '09 term at University of the Sciences in Philadelphia.

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anatomy 11 - 10/29/08 REFLEXES reflexes are rapid,...

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