DEFECATION

Question 1

Defecation

Answer 1

stretching of rectum stimulates defecation reflexes

Question 2

Intrinsic defecation reflex

Answer 2

• works entirely within the myenteric plexus
• stretch signals travel through the plexus to the muscularis, causing it to contract and the internal sphincter to relax
• relatively weak contractions

Question 3

Parasympathetic defecation reflex

Answer 3

• involves spinal cord
• stretching of rectum sends sensory signals to spinal cord
• pelvic nerves return signals, intensifying peristalsis and relaxing the internal anal sphincter
• defecation occurs only if external anal sphincter is voluntarily relaxed