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regulation of gut function Flashcards

1
Q

what is the git nervous system made up

A 
autonomic (extrinsic) 
and 
enteric (intrinsic)
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2
Q

what is the autonomic nervous system made up of

A

symp- fight flight

para- rest and digest

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3
Q

where does teh symp preganglionic fibres arise from

A

thoracic and lumbar spinal cord

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4
Q

what supplies the stomach

A

T6-9

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5
Q

colon

A

L2-5

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6
Q

what is the post ganglionic neurons in the stomach.

A

coeliac ganglion

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7
Q

Small intestine

A

– superior mesenteric ganglion

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8
Q

Colon

A

inferior mesenteric and pelvic ganglion

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9
Q

what is the neurotransmitter

A

noradrelaline

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10
Q

effect of sympathetic nervous system

A

Activation of sympathetic nervous system inhibit activities of gastrointestinal tract

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11
Q

what nerve supplies the para innervation to stomach, small intestsines, proximal colon

A

vagus nerve

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12
Q

where do the preganglionic neurones originate from

A

Preganglionic neurons originate in dorsal vagal complex within brainstem from sacral spinal cord.

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13
Q

what is the nuerotransmitter

A

acetylcholine

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14
Q

how is the gastrointestinal tract stimulated

A

Activation of parasympathetic nervous system stimulates the gastrointestinal tract.

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15
Q

how big are the sympathetic preganglioic fibres

A

small spinal cord

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16
Q

parasymptheric

A

long- near target organ

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17
Q

what else can autonomically control gi functions

A

enteric nervous system

Can also interact with sympathetic and parasympathetic nervous system

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18
Q

where are the nuerones of the enteric nervous system found

A

walls of the gi tract in myenteric plexus and submucosal plexus

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19
Q

what is a plexus

A

Plexus = network of intersecting nerves

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20
Q

what is the enteric nervous system composed of

A 
outer plexus (myenteric or ) 
inner (submucosal plexus)
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21
Q

where is the outer plexus

A

in between the longitudinal and smooth muscle

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22
Q

control

A

motility of gut wall

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23
Q

inner plexus function

A

blood flow and GI secreation

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24
Q

Myenteric (Auerbach’s) plexus controls

A

controls activity of muscle layer of bowel (muscularis propria
controls gut motor (motility) function
tone, velocity of contraction and intensity of contraction.

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25
Q

Submucosal (Meissner’s) plexus controls

A

senses the local environment (gut lumen) -> recognise changes in gut lumen
controls secretion, blood flow, epithelial and endocrine cell function

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26
Q

what happens if food enters the gut lumen

A

Food enters gut lumen and stretches the intestinal smooth muscles

Distension of the gut causes stimulation of the sensory neurons in the myenteric plexus
Chemicals in food stimulates sensory neurons in submucosal plexus

Sequential contraction/relaxation of circular and longitudinal muscle by inhibitory/excitatory neurotransmitter cause peristalsis, which allows food to move along the GI tract

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27
Q

how does the circular muscles move the food

A

contract just behind the bolus of food

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28
Q

what do the longitudinal muscles do

A

contract ahead of the bolus causing it to shorten and widen to receive the bolus

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29
Q

how do the circular and longitudinal muscles work relative to each other

A

opposite
one relaxes
one contracts

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30
Q

what affect can extrinsic e.g. symp or para have on enteric

A

can greatly enhance or inhibit function

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31
Q

what can symp do to enteric nervous system

A

reduces peristalsis
reduces absorption
reduces secretion
reduces blood flow (via enteric nervous system and also directly)

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32
Q

what does para do to enteric nervous system

A

increases peristalsis
increases absorption
increases secretion
increases blood flow

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33
Q

what is Hirschsprung’s Disease

A

Congenital absence of ganglion of myenteric and submucosal of large bowel

enlarged colon

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34
Q

what does it causes

A

Tonal contraction of affected side without reciprocal relaxation/dialted

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35
Q

outcome

A

surgery

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36
Q

what are gut hormones secreated from

A

enteroendocrine cells

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37
Q

where are they secreated

A

stomach
pancrease
small in

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38
Q

what are the 3 types

A

endocrine
paracrine
neurocrine

39
Q

where are endocrine cells

A

the base of intestinal crypts throughout the GI tract, from stomach to colon

40
Q

what are they

A

specialised epithelial cells

41
Q

how do they secreate hormone

A

possess hormone-containing granules concentrated at the basolateral membrane,
adjacent to capillaries, that secrete their hormone in response to a wide range of stimuli

42
Q

how is it stimulated

A

these stimuli include small peptides, amino acids, fatty acids, oral glucose, distension of an organ, and vagal stimulation

43
Q

what is gastrin

A

a hormone which stimulates secretion of gastric juice and is secreted into the bloodstream by the stomach wall in response to the presence of food.

44
Q

where is it synthesised

A

Synthesised in gastric antrum and upper small intestine

45
Q

how is it realased

A

amino acids and peptides in the lumen of the stomach
gastric distension
vagus nerve

46
Q

function

A

gastric acid secretion by parietal cells in stomach

47
Q

when are they inhibited

A

Release inhibited when pH of stomach falls below pH 3

48
Q

what does it do to the mucosa

A

stimulates growth of mucosa in the SI colon stomach

49
Q

what is Secretin

A

Secretin, a digestive hormone

50
Q

what is it secreted by

A

by the S cells of the upper duodenum and jejunum

51
Q

stimulus

A

Major stimulus is the presence of acid in the duodenum (pH falls below 4.5)

52
Q

function

A

stimulates pancreatic bicarbonate secretion (effect potentiated by CCK)
inhibition of gastric acid and gastric emptying
inhibits gastrin, acid secretion, and growth of stomach mucosa
stimulates biliary secretion of bicarbonate and fluid
trophic effect on the exocrine pancreas

53
Q

what’s Cholecystokinin

A

a hormone which is secreted by cells in the duodenum and stimulates the release of bile into the intestine and the secretion of enzymes by the pancreas.

54
Q

stimulus

A

Release stimulated by fat and peptides in the upper small intestine

55
Q

secreated by

A

Secreted by cells most densely located in the small intestine

56
Q

function

A

stimulates pancreatic enzyme release (lipase, amylase, proteases)
stimulates gallbladder contraction and relaxation of the sphincter of Oddi
delays gastric emptying
decreases food intake and meal size
trophic effects on the exocrine pancreas and gallbladder

57
Q

what’s Glucose-dependent insulinotropic peptide (GIP)

A

is a hormone released from the small intestine that enhances the release of insulin following the intake of food

58
Q

secreated by

A

Secreted by mucosal K cells (predominant in the duodenum and jejunum)

59
Q

stimulus

A

GIP released following ingestion of a mixed meal

The only hormone with a response to all 3 macronutrient types (glucose, amino acid, fatty acids)

Likely stimulated by change in intraluminal osmolarity

60
Q

function

A

Stimulates insulin secretion

61
Q

function of motilin

A

Increases gastrointestinal motility

62
Q

what is somatostatin

A

Somatostatin is a universal inhibitor (Endocrine Cyanide)

63
Q

synthesis

A

Synthesized in endocrine D cells of the gastric and duodenal mucosa, pancreas

64
Q

stimulis

A

Release in response to a mixed meal

65
Q

function

A 
gastric secretion 
motility
intestinal and pancreatic secretions
release of gut hormones
intestinal nutrient and electrolyte transport
growth and proliferation
66
Q

Glucagon-like peptide-1 (GLP-1)

A

peptide hormone

67
Q

secreted by

A

Produced in the small intestine and secreted from L cells

68
Q

stimulus

A

Release stimulated by the presence ofhexose and fat

69
Q

function

A

Induces satiety

Increases sensitivity of pancreatic beta-cells to glucose

70
Q

Pancreatic polypeptide function

A

Potential role in satiety

71
Q

stimulus

A

Secretion stimulated by fat

72
Q

where is it secreted from

A

Secreted by pancreatic polypeptide cells cells in the pancreas aka gamma cells

73
Q

Peptide YY function

A

Reduces intestinal motility, gallbladder contraction and pancreatic exocrine secretion

74
Q

released from

A

Released from L cells post- prandially (particularly protein)

75
Q

where is it secreted

A

Secreted from cells found throughout the mucosa of the terminal ileum, colon and rectum

76
Q

where are nuerocrine hormones located

A

Located within nerves in the gut

77
Q

examples of neurocrine hormones

A

Vasoactive intestinal peptide (VIP
Gastrin releasing peptide (GRP
Enkephalins

78
Q

function of Enkephalins

A

increase smooth muscle tone

79
Q

function of GRP

A

→ induces gastrin release

80
Q

vip

A

relaxation of gut smooth muscle

81
Q

what is Zollinger Ellison syndrome

A

– tumour of gastric cells causing overproduction of gastrin and acid resulting in stomach and intestinal ulceration

82
Q

treatment

A
  • treatment with proton pump inhibitor to inhibit acid secretion
    • role for somatostatin analogues to halt tumour growth and reduce secretion
83
Q

3 phases of gastric secreation

A

cephalic
gastric
intestinal

84
Q

how is the cephalic phase

stimulated

A

Smell, thought, sight and taste of food and tactile sensations of food in the mouth stimulate brain stem

85
Q

how is it stimulated

A

Parasympathetic nervous system via the vagus nerves stimulate the enteric plexus

86
Q

what hormones are secretaed

A

Postganglionic neurons stimulate secretion of gastrin, acid (parietal cells) and digestive enzymes (chief cells)

87
Q

what affect do they have

A

Gastrin released into bloodstream and induces secretion by parietal and chief cells

88
Q

what stimultaes the gastric phase

A

This phase lasts 3-4 hours

Food arrives in stomach and distension causes signals via the vagus nerve to the brainstem

89
Q

what does it stimulate

A

This in turn stimulates stomach secretion

90
Q

how is the stomach secretion increased

A

Distension of the stomach and chemicals in food also activate the enteric nervous system to increase stomach secretion

91
Q

how is the intestinal phase stimulated

A

Chyme in the duodenum with pH<2 or lipids stimulate stretch and chemoreceptors that generate action potentials to the brainstem whereby they inhibit the parasympathetic nervous system, thereby inhibiting gastric secretions.

92
Q

next

A

Local reflexes activated by acid and lipids also act on the enteric nervous system to inhibit gastric secretions.

93
Q

what hormones are relased

A

Secretin, gastric inhibitory polypeptide and cholecystokinin, released by the duodenum inhibit gastric secretions.

nuero (36 decks)

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