S2- Physiology

Question 1

What are the 3 sympathetic nerves supplying the GI tract? Which vertebral levels do each arise from?

Answer 1

Greater. T5-T9
Lesser T10-11
Least splanchnic nerves. T12

Question 2

Where do the greater, lesser and least splanchnic preganglionic fibres synapse with the post ganglionic fibres?

Answer 2

Greater- Coeliac ganglia
Lesser- Superior Mesenteric ganglia
Least- Inferior Mesenteric Ganglia

Question 3

What are the two main parasympathetic nerves, from which spinal levels do they arise from and Which parts of the GI system do the vagus and pelvic splanchnic nerve innervate?

Answer 3

Oesophagus to transverse colon Vagus. Brainstem

Transverse colon to anus pelvic splanchnic nerve S2-S4

Question 4

What are the two main plexuses of the enteric nervous system called?

Answer 4

Meissner’s and Auerbach’s plexuses

Question 5

In which layers are the Meissner’s and Auerbach’s plexus located and what do each control?

Answer 5

Meissners- Submucosa– Secretions and Blood flow

Auerbach’s (Also called Myenteric)- Between circular and longitudinal muscles, controls motility

Question 6

What type of effect does the peptide somatostatin have?

Answer 6

Paracrine

Question 7

What type of effect does the Gastrin Releasing Peptide have?

Answer 7

Neurocrine

Question 8

Where in the stomach are G cells found?

Answer 8

In the antrum

Question 9

What type of cells secrete cholecystokinin and what stimulates its release, where are these cells found, what effect does CCK have?

Answer 9

I cells– fat and protein– duodenum and jejunum– contracts gallbladder and stimulates pancreas

Question 10

What cells secrete secretin and what stimulates its release, where are these cells found and what effect does secretin have?

Answer 10

S cells–H+ and FAs– in duodenum– increases HCO3- secretion from pancreas, decreases gastric acid secretion

Question 11

3 places in the GI tract where there is tonic contraction?

Answer 11

Upper stomach
Ileocaecal valve
Internal anal sphincter

Question 12

Define paralytic ileus

Answer 12

Obstruction of the intestine due to paralysis of the intestinal muscles

Question 13

Define achalasia

Answer 13

Failure of the LOS to relax

Question 14

Four functions of mucus in the GI tract?

Answer 14

Protect against the acidic environment of the stomach
Protect against bacteria in the SI (contains antibacterial compounds)
Harbours bacteria in large intestine (provides partial food source)

– Lubricates

Question 15

What types of sodium channels are found in the colon?

Answer 15

ENaC