The defecation reflex
A)is initiated when mass movements force fecal material into the rectum, stimulating stretch receptors in the rectal wall
B)involves relaxation of the internal anal sphincter
C)involves contraction of the sigmoid colon and rectum
D)can be overridden by voluntary contraction of the external anal sphincter
E)has all of the above characteristics

Question

Quizplus · Accepted Answer

The defecation reflex is initiated when mass movements force fecal material into the rectum, stimulating stretch receptors in the rectal wall. This results in contraction of the sigmoid colon and rectum and relaxation of the internal anal sphincter. However, the reflex can also be overridden by voluntary contraction of the external anal sphincter. Therefore, all of the above characteristics are correct.

The Defecation Reflex