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Flashcards in Regulation of Digestion Deck (47):
1

Where and how is cellulose broken down?

In the gut, by fermentation by the gut microbiome

2

Important role of the pyloric valve in amylase function

Amylase is pH-sensitive.
Pyloric valve separates the low-pH stomach environment from the neutral duodenum

3

Elements controlling gut

Nervous system (CNS, PNS, enteric)
Endocrine system
Smooth muscle and associated pacemakers

4

Layers of the enteric nervous system

Longitudinal muscle
Myenteric plexus
Circular muscle
Deep muscular plexus
Mucosal plexus
Muscularis mucosae
Mucosa

5

Structures attached to enteric longitudinal muscle

Myenteric plexus
Tertiary plexus

6

Intrinsic neurons in the ENS

Sensory, interneurons, excitatory and inhibitory motor neurons

7

Primary functions of the ENS

Motility, water and salt transport

8

Number of basic ENS motility patterns

Three

9

Basic ENS motility patterns

Fed state
Fasted state
Mass movement contraction

10

Characteristics of fed-state motility pattern

Stomach relaxation (size of fist --> much larger)
Segmentation in small intestine
Peristalsis
Retropulsion/antiperistalsis, in some situations

11

Segmentation

Local stationary constrictions in small intestine.
No net forward movement of chyme
Mixes intestine contents

12

Characteristics of fasted-state motility pattern

Migrating motor complex moves through small intestine

13

Characteristics of migrating motor complex

Slowly moving constriction of intestine
Cleans out debris (bacteria, cell fragments)
Takes ~90 minutes from pylorus to anus

14

Characteristics of mass movement contraction motility pattern

In colon, rectum
Involved in defecation

15

Difference between peristalsis and segmentation

There is no net forward movement in segmentation

16

Where does the ENS regulate motility patterns?

All parts of the gut except upper oesophagus

17

Pacemaker cells in gut

Interstitial cells of Cajal

18

Role of interstitial cells of Cajal

Produce slow wave potentials in smooth muscle

19

Which type of cell is an interstitial cell of Cajal?

Modified smooth muscle cell

20

Role of slow wave potentials

Keep enteric smooth muscle just below threshold
Can be easily depolarised to threshold by CNS

21

Plexi containing neurons in ENS

Submucosal plexus
Myenteric plexus

22

Feed-forward reflexes of ENS

Cephalic reflex
Gastro-colonic reflex

23

Cephalic reflex

Thought of, smell, sight of food can trigger:
Salivation
Relaxation of stomach
Segmentation in intestine

24

Gastro-colonic reflex

Food entering stomach can trigger defecation

25

Feedback reflexes of ENS

Inhibition of gastric emptying

26

Factors inhibiting gastric emptying

Acid in duodenum
Excess material in colon

27

Effects of gastrin

Stimulates gastric acid secretion
Stimulates mucosal growth

28

Target of gastrin

Enterochromaffin-like cells (ECL cells)
Parietal cells

29

Stimuli for gastrin release

Partially digested protein in stomach
Stomach distension
Neural signals, particularly via vagus nerve

30

Effects of cholecystokinin

Stimulates gallbladder contraction
Stimulates pancreatic enzyme release
Inhibits gastric emptying
Inhibits gastric acid secretion
Promotes satiety

31

Targets of cholecystokinin

Stomach, pancreas, gallbladder

32

Cells secreting cholecystokinin

I-cells in intestine
Segrete into duodenum

33

Stimulus for cholecystokinin release

Presence of fatty acids or some amino acids in chyme
CCK-releasing protein (secreted by enterocytes)
Parasympathetic stimulation from vagus nerve

34

Effect of secretin

Stimulates bicarbonate secretion
Inhibits gastric emptying
Inhibits gastric acid secretion

35

Stimulus for secretin release

Acid in small intestine

36

Targets of secretin

Pancreas, stomach

37

Cells releasing gastrin

G-cells in stomach antrum

38

Cells releasing secretin

S-cells in duodenum.
In crypts of Lieberkuhn

39

Effects of motilin

Stimulates migrating motor complex

40

Stimulus for motilin release

Released periodically during fasting period (every 1-2 hours)
Release inhibited by eating a meal

41

Targets of motilin

Stomach, intestinal smooth muscle

42

Gastric inhibitory peptide effects

Stimulates insulin release (feedforward)
Inhibits gastric emptying
Inhibits gastric acid secretion

43

Gastric inhibitory peptide target

Beta-cells of pancreas

44

Gastric inhibitory peptide stimulus

Glucose, fatty acids, amino acids in small intestine

45

Glucagon-like peptide 1 effect

Promotes satiety
Stimulates insulin release
Inhibits gastric acid secretion, gastric funciton

46

Glucagon-like peptide 1 stimulus

Fats and carbohydrates in gut lumen

47

Glucagon-like peptide 1 target

Endocrine pancreas