DEFECATION

 

Neurological centers and pathways are similar to those of urination. The sympathetic system is inhibitory over the descending colon and rectum, and excitatory over the internal anal sphincter. The parasympathetic system is responsible for the excitatory activity of the rectum and inhibitory of the internal anal sphincter.

 

The central and peripheral pathways from and to the rectum connect to the centers of the brain stem and the cerebral cortex through the spinoreticular and reticulospinal tracts. However, these pathways are complex and it has been suggested that other tracts included in the lateral and dorsal funculi may be involved.