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Flashcards in GI Hormones and NT Deck (59):
1

Neural stimulation -->

thought and sight

2

Chemical stimulation -->

taste and odor

3

Nutrient stimulation -->

epithelial cells of GI tract

4

Neural, chemical, nutrient and mechanical stimulation lead to

the release of peptides and transmitter from mucosal cells into blood stream or place of action

5

GI system functions are regulated:

locally by hormones (more than 30) and local reflexes
- Larges endocrine organ

6

Autonomic Nervous System functions

Regulate local reflexes
Initiates gastric digestion
Mediates larger movements

7

What are the phases of digestion

Cephalic
Gastric
Intestinal

8

Cephalic phase

Via vagus nerve
PS excites pepsin and acid production
-30%

9

Gastric phase:

Local nervous secretory reflexes
Vagal reflexes
Gastrin-histamine stimulation
-60%

10

Intestinal phase

Nervous mechanisms and hormonal mechanisms
Where nutrients is absorbed
10%

11

Mechanism of secretion:

Nerve or hormonal stimulation --> trasnport of Cl into the cell --> activates Na ions --> creates osmotic force --> creates osmosis of water in the interior --> causing increased volume and hydrostatic pressure which initiates minute openings of secretory border releasing mucus

12

Endocrine signaling

Peptide hormone is released into the bood and reches its target cells via circulation

13

Paracrine signaling:

Form of cell signaling in which the target cell is NEAR the signal-releasing cell

14

Autocrine signaling:

Cell secretes a hormone or chemical messenger that bings to autocrine receptors ON THE SAME CELL, leading to changes

15

Neurocrine signaling:

CHEMICAL SYNAPSES
From one neuron to the other through synapses

16

***Gastrin is secreted by:

G cells or endocrine cells of the stomach

17

Gastrin is stimulated by:

Ingestion of meal --> distention of the stomahc, products of proteins, gastrin releasing peptide

18

***Primary actions of gastrin:

Stimulation of gastric acid secretion
Stimulation of growth of the gastric mucosa
Stimulates stomach motility

19

***Cholecystokinin (CCK) is produced by:

Enteroendocrine cells or I cells of the duodenum and jejunum

20

CCK is secreted due to :

Digestive products of fat, fatty acids, and monoglycerides

21

***Function of CCK cells

1. Act on CCK-A to stimulate production of pancreatic enzymes
2. Strongly contracts gall bladder
3. Relaxes hepatopancreatic sphincter to release pancreatic juice and bile
4. Inhibits stomach contraction
5. Inhibits appetite to prevent overeating through sensory afferent nerve stimulation

22

***Secretin is secreted by:

Enterchromaffin cells or S cells in upper small intestinal mucosa

23

Secretin is stimulated by:

Acidity in the duodenum

24

***Secretin stimulates:

Pepsin secretion
Pancreatic bicarbonate secretion
Biliary bicarbonate secretion

25

***Secretin inhibits:

Gastric acid secretion and intestinal motility

26

***Gastric Inhibitory Peptide (GIP) is secreted by:

Epithelial cells in upper small intestinal

27

GIP is stimulated by

Increased fatty acids and amino acids
Increased carbs

28

***GIP inhibits

stomach motility and secretion (slows gastric emptying)

29

***GIP can stimulate:

Insulin secretion at very very low levels

30

***Motilin is secreted by:

Endocrine M cells in stomach and duodenum during fasting

31

*** Motilin stimulates:

Gastrointestinal motility - interdigestive myoelectric complexes

32

***Motilin secretion is inhibited by:

After ingestion by mechanisms that are unknown

33

Define Interdigestive myoelectric complexes

Moves through the stomach and small intestine every 90 minutes in a fasted person

34

Vasoactive Intestinal Polypeptide (VIP) is secreted by:

Enteric neurons in small intesting

35

VIP is really not a hormone but a:

Neuropeptide/neurotransmitter bc it is very widely distributed in peripheral and CNS

36

VIP Functions:

1. Induces intestinal vasodilation
2. Relaxes smooth muscles of trachea, stomach, gallbladder and sphincters
3. Decrease HCl secretion
4. Increases intestinal secretion

37

Ghrelin was named because:

its ability to stimulate secretion of growth hormones in pituitary gland

38

***Ghrelin is synthesized:

mainly in the stomach but also in the pituitary and hypothalamus

39

***Ghrelin functions:

Increases hunger by acting on hypothalamic feeding centers

40

Blood ghrelin levels:

Lowest after eating
Low in obese
High in anorexia

41

Define Prader-Willi Syndrome

Extreme obesity with uncontrollable and voracious appetite
Plasma ghrelin levels are super high

42

Hormone actions in GI

LOOK AT SLIDE PICTURE

43

Enteric Nervous System (ENS) functions

Acts below the level of consciousness (not our control)
Coordinates basal gut movements (pacemaker cells) and secretions

44

ENS neurons are where:

Submucosal plexus of Meissner (sensory)
Myenteric plexus of Auerback (motor)

45

Most commonate NT of intrinsic nervous system:

ACh

46

Enteric nerves can:

synthesize, store and release more than one type of transmitter

47

PS activation + ACh

ACh acts via muscarinic M3 to stimulate secretion and to increase smooth muscle tone and motility

48

Drugs that decrease vagal tone:

Atropine
Butylscopolamine

49

Drugs that decrease vagal tone by unintended side effects

Antihistamines, TCA and neuroleptics

50

Drugs to increase vagal tone to induce bowel contraction:

Bethanechol
Neostigmine

51

NE from sympathetic innervation causes:

Vasoconstriction and contraction of sphincters via adrenergic alpha 1
Relaxes intestinal smooth muscles through adrenergic beta 2 (↑ cAMP)
Inhibit ACh release via stimulation of presynaptic alpha 2 (↓ cAMP)

52

Serotonin input:

Increases ACh release via 5HT4 which increases motility
Excitation of sensory neurons via 5HT3 receptors leads to pain and emesis

53

5HT4 receptor agonists drugs:

Tegaserod
Metoclopramide
Cisapride

54

5HT3 receptor antagonists drugs:

Ordansetrone and derivatives

55

Nitric Oxide function

Reduces intestinal ACh release and relaxes intestinal smooth muscles

56

NO is formed by:

Enteric enurons by neuronal NO synthase

57

Histamine is secreted from:

Enterchromaffin like cells (ELC) in the stomach

58

Histamine does what:

Acts on parietal cells via H2 receptors to stimulate acid secretion

59

Somatostatin (SST) function:

Acts on receptors which mediate adenylate cyclase inhibition
Inhibits the secretion of many hormones like VIP
- Used to control upper GI bleeding