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Gastrointestinal > Physiology > Flashcards

Physiology Flashcards

1
Q

What is the function and therefore role of the orad stomach?

A

To relax and cause expansion allowing space to receive food bolus

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2
Q

What is the function and therefore role of the caudad stomach?

A

To contract to cause churning of food, reducing bolus size and mixing it with gastric secretions to form chyme

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3
Q

What types of electrical/mechanical activity occur in the caudad region of the stomach?

A

Continuous slow waves of depolarisation that may or may not reach contraction threshold
Peristaltic contractions propelling chyme to pylorus
Retropulsion causing smaller chyme particles and mixing

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4
Q

What causes relaxation of the orad stomach?

A

Vagal stimulation

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5
Q

What adaptations does the small intestine have for absorption?

A

Folds of kerckring, villi, microvilli

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6
Q

What is segmentation in the SI?

A

Back and forth movement of chyme due to alternate contraction and relaxation of circular smooth muscle.

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7
Q

What electrical activity controls segmentation?

A

Pacemaker cells causing the Basal Electrical Rhythm.

Affected by sympathetic and parasympathetic activity

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8
Q

What is the migrating motor complex?

A

The strong, slow, peristalsis in the SI between meals

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9
Q

What does the MMC do?

A

Clear debris, mucous, and dead cells from SI

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10
Q

What inhibits MMC?

A

Feeding, vagal activity, gastrin, CCK

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11
Q

What triggers MMC?

A

Motilin hormone

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12
Q

Gastrin is made in ____ cells in the ____ and ____

A

G cells
Gastric antrum
Duodenum

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13
Q

What is the role of gastrin?

A

Stimulate H+ secretion from parietal cells

Stimulate growth of gastric mucosa

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14
Q

Secretin is made in ____ cells in the ___

A

S cells

Duodenum

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15
Q

What is the role of secretin?

A

Promote secretion of pancreatic/biliary HCO3-

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16
Q

What stimulates release of secretin?

A

Fatty acids and H+ in the lumen

17
Q

Cholecystokinin is made in the ___ cells in the ___ and ___

A

I cells
Duodenum
Jejunum

18
Q

What is the role of cholecystokinin?

A

Inhibit gastric emptying
Causing pancreatic enzyme secretion
Relaxing the Sphincter of Oddi allowing bile from gall bladder to enter the duodenum
Activates secretin

19
Q

What stimulates release of CCK?

A

Fatty meal in the duodenum

20
Q

What does glucose-dependent insulinotropic peptide (GIP) do?

A

Stimulates release of insulin from beta cells in pancreas

Inhibits gastric emptying

21
Q

What does glucagon-like peptide-1 do?

A

Stimulates insulin secretion
Inhibits glucagon secretion from pancreatic alpha cells
Decreases gastric emptying and appetite

22
Q

What does ghrelin do?

A

Stimulates appetite

23
Q

What drives the BER of slow wave activity?

A

Interstitial cells of Cajal - pacemaker cells

24
Q

How does electrical activity pass between ICCs and to muscle cells?

A

Via gap junctions - contraction occurs as a synchronous wave

25
Q

What causes the upstroke and downstroke of potential in smooth muscle cells?

A

Upstroke: Ca2+ influx via L-type channels
Downstroke: K+ efflux via channels

26
Q

What happens to the baseline membrane potential with successive action potentials (in smooth muscle cells)?

A

It increases, allowing greater chance of threshold being met

27
Q

What effect does more action potentials have?

A

More forceful contraction

28
Q

What stimuli affect the BER?

A

Neuronal stimuli - enteric and autonomic
Hormonal stimuli
Mechanical stimuli

29
Q

What do (preganglionic) parasympathetic fibres release and where?

A

Acetyl choline at ganglia within the ENS

30
Q

What do preganglionic sympathetic fibres release and where?

A

Acetyl choline at prevertebral ganglia

31
Q

What does increased parasympathetic innervation cause?

A

To the stomach, pancreas, and small intestine:
Increased secretion
Increased blood flow
Increased muscle contraction

32
Q

What does decreased parasympathetic innervation cause?

A

Relaxation of various sphincters

Relaxation of the stomach

33
Q

What does increased sympathetic innervation cause?

A

Increased sphincter tone

34
Q

What does decreased sympathetic innervation cause?

A

decreased motility, secretion, and blood flow

35
Q

Name the 2 plexuses of the ENS and give their locations

A

Myenteric (Auerbach’s) plexus - between 2 muscularis externa layers
Submucosal (Meissner’s) plexus, in the submucosa

36
Q

What happens in peristalsis in the receiving segment?

A

Longitudinal muscle contracts, circular muscle relaxes

37
Q

What happens in peristalsis in the propulsive segment?

A

Longitudinal muscle relaxes, circular muscle contracts

Gastrointestinal (5 decks)

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