CONTROL BY THE CENTRAL NERVOUS SYSTEM OF RECTAL SMOOTH MUSCLE

Abstract

There is a tonic mechanism in the midbrain controlling the activity of the smooth muscle of the rectal wall. After transection of the brain stem just cephalic to the acoustic colliculi, the smooth muscle of the rectal wall becomes hyperactive to stretch stimuli and strong waves of contraction occur which expel the balloon from the rectum. After a lower section through the medulla, the stretch responses are lost, no waves of contraction occur, the wall accommodates to a larger volume than in the normal cat, and the balloon is not expelled.