Explain how damage to the somatic nervous system would affect the defecation reflex
What will be an ideal response?
Defecation would no longer be under our voluntary control if the somatic nervous system was damaged. The external anal sphincter is constructed of skeletal muscle. As this sphincter is voluntary, it is supplied by somatic motor neurons controlled by the cerebral cortex. During the defecation reflex, impulses from the cerebral cortex trigger relaxation of the external anal sphincter and contraction of the levator ani muscle. The cerebral cortex stimulates voluntary relaxation of the external anal sphincter; the levator ani muscle contracts, elevating the anus. Together, these movements normally allow the feces to pass, but cannot be controlled with damage to the voluntarily controlled somatic nervous system.
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