Defaecation reflex
Stimulus: rectal distension
During defecation there is:
- Contraction of the rectum
- Relaxation of the internal anal sphincter
- Initial contraction then relaxation of the external anal sphincter (voluntary control)
- Contraction of abdominal wall muscles
- Relaxation of pelvic wall muscles
Impaired with lesion below T12
Conscious control via pudendal (s2-4) nerve
