L18 - Digestion and NS

Question 1

Somatic NS - chewing, swallowing, peristalsis in the oesophagus and opening key sphincters

Visceral neruons - salivation, primary peristalsis, all functions from stomach to anus

Answer 1

Somatic NS - chewing, swallowing, peristalsis in the oesophagus and opening key sphincters

Visceral neruons - salivation, primary peristalsis, all functions from stomach to anus

Question 2

What happens when we see or smell food?

Answer 2

Initiates the cephalic phase of digestion (salivation, gastric relaxation, gastric acid secretion)

• The more palatable the food, the greater the response (requires memory of previous meals)
• Requires cortex, vagal pathways to activate acid secretion and relaxation

Question 3

Sucking is essential for early survival - has hedonistic component. What does hedonistic mean?

Answer 3

Means involving pleasure

Question 4

What cortex is the tongue controlled by?

Answer 4

Motor cortex

Question 5

What is swallowing controlled by?

Answer 5

Motor pattern generator in brain stem

Question 6

Achalasia

Answer 6

A condition in which the muscles of the lower part of the oesophagus fail to relax, preventing food from passing into the stomach - leads to acid reflux

Question 7

What nerve is primary peristalsis controlled by?

Answer 7

CNS via Vagus

Question 8

Secondary peristalsis is part of CNS or ENS?

Answer 8

ENS

Question 9

ENS: Stomach has important control system via pacemaker cells in antrum known as? What do they do?

Answer 9

Interstitial cells of Cajal -serve as electrical pacemakers and generate spontaneous electrical slow waves in the gastrointestinal (GI) tract. pushing it against pyloric sphincter to break it down

Question 10

In which parts do these actions occur

a) digestion
b) absorption
c) propulsion

Answer 10

a) Digestion (duodenum, jejunum)
b) Absorption (nutrient: duodenum, jejunum; water: ileum, colon)
c) Propulsion (whole length)

Question 11

6m small intestine, 1m large intestine. SA of small intestine has villi which increase SA:V hence more SA than skin

Answer 11

6m small intestine, 1m large intestine. SA of small intestine has villi which increase SA:V hence more SA than skin

Question 12

Coeliac disease

Answer 12

Gluten-intolerant as villi fall off of small intestine and mucosa becomes smooth, decreasing SA:V by 100 fold - nutrients absorbed decreased

Question 13

ENS
•Contained entirely within the intestinal wall and runs its full length –GI tract only organ with its own complete nervous system
•More neuron cell bodies than spinal cord (about 300,000,000 in humans)
•Can operate without CNS, but modulated by input from brain via vagus and sympathetic nervous system
•Begins at upper esophageal sphincter continues to vagus

Answer 13

ENS
•Contained entirely within the intestinal wall and runs its full length –GI tract only organ with its own complete nervous system
•More neuron cell bodies than spinal cord (about 300,000,000 in humans)
•Can operate without CNS, but modulated by input from brain via vagus and sympathetic nervous system
•Begins at upper esophageal sphincter continues to vagus

Question 14

Secretomotor neurons

Answer 14

Secretion and absorption of water and salt from inside of body to inside of lumen
-Also directly regulate part of the nutrient absorptive process

Question 15

Intrinsic sensory neuron are part of a recurrent excitatory circuit. It requires intrinsic inhibition to prevent spasm.

Answer 15

Intrinsic sensory neuron are part of a recurrent excitatory circuit. It requires intrinsic inhibition to prevent spasm.