Question

Explain how contraction the gastrointestinal smooth muscle is intrinsically controlled

Answer 1

1. When a large bolus of ingested food enters the smooth muscle it causes stretching of the wall of gut that stimulates the nerves present in the smooth muscle of the gut to release of neurotransmitter from the site of stimulation into the smooth muscle.

2. Due to the release of neurotransmitter the membrane potential becomes positive than the resting membrane potential (-50 to 60 mV) and the membrane potential becomes 5 to 15 mV thus the depolarization occurs. The changes in the membrane potential in the site of stimulation along the smooth muscle of gut is spread to adjacent section of the muscle, because the smooth muscle cells are electrically coupled that causes slow wave along the digestive tube.

3. The involuntary motility of gut causes to pass the food occurs due to coordinated contraction of the smooth muscle which is the result of the 2 electrical activity of the smooth muscle cells that are slow waves and spike potential.

4. This slow wave activity is the intrinsic property of the smooth muscle that controls the development of the spike potential that is the true action potential which arises from the crest of the slow wave and plays role in the smooth muscle contraction of the gut to perform the involuntary motility of the gut.