L2 Regulation of the Gastrointestinal Tract Motility

Question 1

Describe the motility of the GIT explaining how this is regulated including the role of the enteric nervous system and its modulation by the autonomic nervous system

Answer 1

Peristalsis
Happens in the small and large intestine
The tunica muscularis layer consists of an inner circular layer and an outer longitudinal layer of smooth muscle. Contraction of the CM and relaxation of the LM leads to elongation and constriction. Relaxation of the CM and contraction of the LM leads to dilation. This pushes food down in a peristalsis wave.

Segmental
Small intestine
Rhythmic contraction of the circular muscle back and forth by mixing and packing

Haustration
Large intestine
Formation of sacs which store and propel contents

The digestion phase of peristalic contractions passes over short segments of the small intestine. Whereas inter digestive phase pass over large segments to clear out undigested material and keep control of bacterial populations.

Question 2

Discuss the concept of regulation of the GIT, through endocrine, paracrine and neural mechanisms

Answer 2

Chemo and mechanoreceptors

Intrinsic control is due to smooth muscle of the gut being myogenic

Endocrine released into the blood stream

Paracrine released by loal diffusion

Nervous enteric intrinsic control

Autonomic and parasympathetic