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 and contraction of the sigmoid colon and rectum.
C) can be overridden by voluntary contraction of the external anal sphincter.
D) both (a) and (b) above.
E) all of these answers.

Question

Quizplus · Accepted Answer

The defecation reflex involves all the processes mentioned: initiation by stretch receptors when fecal material enters the rectum, relaxation of the internal anal sphincter, contraction of the sigmoid colon and rectum, and the ability to override the reflex by voluntary control of the external anal sphincter.

The Defecation Reflex