Lecture 29

Question 1

Briefly describe the regulation of fore-stomach contractions associated with the vagal nerve:

Answer 1

1. Sensory information from the stomach is transmitted by vagal nerve
2. Processed in the medulla
3. Efferent signals are from the vagus, via the dorsal vagal nucleus

Question 2

What part of the stomach is “fre-est” from nerve activity?

Answer 2

abomasum

Question 3

What is the name of the centre in the medulla that the vomiting reflex is initiated from?

Answer 3

Emetic centre

Question 4

What are the events associated with vomiting?

Answer 4

1. Prodromal early events occur- these are typically associated with hyper-salivation, cardiac rhythms and potentially defecation
2. Salivation stimulates swallowing-associated with the relaxation of the lower oesophageal sphincter
3. Anti-peristalsis begins in small intestine
4. The duodenum is initially relaxed by then undergoes a giant contraction that will move the digestive matter into the stomach
5. After the retrograde giant contraction the (duodenal activity is one again inhibited)
6. Then followed by retrograde antral contractions and relaxation of the digestive tract that is above that
7. Vagally mediated contraction of the oesophageal longitudinal muscle allows for entrance of the gastric contents
8. Retrograde anal contractions move the contents of the small intestine into the body of the stomach and the fundus
9. Retching now occurs that involves the movement of the digestive matter in and out of the lower oesophagus
10. Pressure in the stomach increases to a point where there is opening of the upper esophageal sphincter and the contents are expelled in a final push from the abdominal muscles and the diaphragm
11. As the vomit passes up the pharynx, glottis and nasopharyngeal opening will close, preventing the possibility of aspiration and nasal regurgitation