Human Anatomy & Physiology (9th Edition)

Published by Pearson
ISBN 10: 0321743261
ISBN 13: 978-0-32174-326-8

Chapter 12 - The Central Nervous System - Review Questions - Page 481: 35

Answer

Paralysis is impairment or inability to execute movement of a part or parts of the body due to damage of relevant parts of the central or peripheral nervous system. Flaccid paralysis and spastic paralysis are two kinds of paralysis are two kind of paralysis that may result from neural injury. There causes are different and so are their clinical manifestations: A. Spastic paralysis is caused by damage to upper motor neurons in the primary motor cortex of the cerebrum. The consequence is that voluntary movements cease in the relevant muscles . However, reflex stimuli continue to reach the muscles, sporadically. These stimuli will keep the muscles alive. B. Flaccid paralysis is caused by injury to ventral horn cells or ventral roots of the spinal cord. When these neurons are damaged, motor impulses cease to reach relevant skeletal muscles.As a result these skeletal muscles lose the ability to move,either voluntarily, or involuntarily.

Work Step by Step

Flaccid paralysis and spastic paralysis are two kinds of paralysis that may result from neural injury. Their causes are different and so are their clinical manifestations: A. Spastic paralysis. This variety is caused by damage to upper motor neurons in the primary motor cortex of the cerebrum. The result of serious damage to the neurons of this area is that motor stimuli cease to reach the relevant muscles. The consequence is that for the affected muscles,voluntary movement cesses. However, reflex stimuli continue to reach the muscles, sporadically. As long as these reflex stimuli continue , the muscle(s) will not atrophy and die ,but it may shorten. B. Flaccid paralysis is probably a more serious condition. This condition is caused by injury to ventral horn cells or ventral roots of the spinal cord. As a result, motor impulses cease to reach relevant skeletal muscles. Consequently these skeletal muscles cannot move either voluntarily or involuntarily. Without artificial stimulation the affected muscles will atrophy and die.
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