During defecation,
A) stretch receptors in the rectal wall activate sympathetic centers in the spinal cord.
B) stretch receptors in the rectal wall activate parasympathetic centers in the spinal cord.
C) stretch receptors in the rectal wall activate both sympathetic and parasympathetic centers in the spinal cord.
D) the internal anal sphincter is consciously relaxed.
E) the external anal sphincter contracts.

Question

Quizplus · Accepted Answer

Stretch receptors in the rectal wall activate parasympathetic centers in the spinal cord which increase peristalsis in the colon and relaxation of the internal anal sphincter. This allows stool to enter the rectum and pushes against the external anal sphincter, which can voluntarily be relaxed to allow defecation.

During Defecation