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Chapter 13 Spinal Control of Movement

Chapter 13 Spinal Control of Movement - Chapter 13 Spinal...

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Sheet1 Page 1 Chapter 13 Spinal Control of Movement Skip pages 433-437 S Each muscle fiber is innervated by a single axon a The cell bodies of lower motor neurons are located in the ventral horn of the spinal cord h Axons of lower motor neurons form the ventral roots, and then h join sensory axons in mixed spinal nerves n The ventral horn is enlarged in spinal cord segments that innervate the arms and the legs s Distribution of lower motor neurons within the ventral horn h Motor neurons controlling axialmuscles lie medial to those controllingdistal muscles h Motor neurons controlling flexors liedorsal to those controlling extensors c Alpha motor neurons make the muscle
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Sheet1 Page 2 contract h A motor unit is a single alpha motorneuron and the muscle fibers it innervates h A motor neuron pool is all thealpha motorneurons that innervate one muscle m Action potential frequency is one way to control the force of muscle contraction c Amyotrophic Lateral Sclerosis (ALS) h h Selective degeneration of a motor neurons in spinal cord and brainstem, and upper motor neurons in cortex h Progressive muscle weakness, wasting of skeletal muscles h h Does not affect sensations, intellect or cognitive functions h Relatively rare disease, afflicting one out of every 20,000 h
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