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BRS Term 2 > Regulation of gut function (42) > Flashcards

Regulation of gut function (42) Flashcards

1
Q

How is the gut nervous system divided?

A
  • autonomic/extrinsic–> sympathetic + parasympathetic

- enteric/intrinsic

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2
Q

Where do the sympathetic preganglionic neurones that supply the gut arise from in the spinal cord?

A

thoracolumbar region

stomach: T6-9
colon: L2-5

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3
Q

What ganglion does the supply to the stomach come from?

A

coeliac

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4
Q

What ganglion does the supply to the small intestine come from?

A

superior mesenteric

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5
Q

What ganglion does the supply to the colon come from?

A

inferior mesenteric and pelvic

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6
Q

What is the main neurotransmitter involved in the sympathetic nervous system supply to the gut?

A

norepinephrine

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7
Q

What happens to the GI tract when the sympathetic nervous system is activated?

A

activities are inhibited

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8
Q

What is the parasympathetic innervation to the GI tract and where do the preganglionic neurons originate?

A
  • vagus nerve supplies stomach, small intestine and proximal colon
  • pelvic nerve supplies distal colon
  • preganglionic neurons originate in dorsal vagal complex (vagal nerves) within brainstem and from sacral spinal cord (pelvic nerves)
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9
Q

What is the main neurotransmitter involved in the parasympathetic nervous system supply to the gut?

A

acetylcholine

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10
Q

What happens to the GI tract when the parasympathetic nervous system is activated?

A

GI tract is stimulated

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11
Q

What is the difference between the placement of the ganglia in the sympathetic and parasympathetic nervous systems?

A
  • sympathetic ganglia = near spinal cord, so short preganglionic axons
  • parasympathetic ganglia = near target organ, so long preganglionic axons
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12
Q

What is a plexus?

A

a network of intersecting nerves

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13
Q

Where is the submucosal plexus located?

A

in submucosal layer of the GI tract

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14
Q

Where is the myenteric plexus located?

A

in between the circular muscle layer (inner) and longitudinal muscle layer (outer)

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15
Q

What is the function of the submucosal plexus?

A
  • senses the local environment in the gut lumen e.g. change in pH
  • controls secretion, blood flow, epithelial and endocrine cell function
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16
Q

What is the function of the myenteric plexus?

A
  • controls activity of muscularis externa
  • senses stretch
  • controls gut motor function: tone, velocity and intensity of contraction
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17
Q

How does peristalsis work?

A
  • wave of muscular contractions moves the bolus through the small intestine
  • circular and longitudinal muscles work in opposite ways–> 1 contracts while the other relaxes
  • circular muscles contract behind bolus of food
  • longitudinal muscles ahead bolus contract, whereas behind relax
18
Q

What is Hirschsprung’s disease?

A
  • congenital absence of myenteric and submucosal ganglions
  • tonal contraction without reciprocal relaxation
  • enlarged colon
  • most require surgery
19
Q

What are endocrine gut hormones?

A
  • secreted by enteroendocrine cells
  • hormones released into bloodstream
  • gastrin, CCK, secretin, GIP, motilin
20
Q

What are paracrine gut hormones?

A
  • secreted by enteroendocrine cells
  • hormone that acts only within its vicinity
  • diffuses through extracellular space
  • somatostatin, histamine
21
Q

What are neurocrine gut hormones?

A
  • secreted by postganglionic non-cholinergic neurons of enteric nervous system
  • affects ‘nerves’
  • vasoactive intestinal peptide (VIP), gastrin release peptide (GRP) and enkephalins
22
Q

What hormones use both endocrine and paracrine mechanisms?

A

GLP-1, pancreatic polypeptide and peptide YY

23
Q

What are enteroendocrine cells?

A
  • specialised epithelial cells located at base of intestinal crypts throughout GI tract (stomach–>colon)
  • have granules at basolateral membrane, adjacent to capillaries, that secrete hormone in response to stimuli: small peptides, AAs, fatty acids, glucose, organ distention and vagal stimulation
24
Q

What gut hormones are released in the stomach?

A
  • gastrin
  • ghrelin
  • somatostatin
  • histamine
25
Q

What gut hormones are released in the duodenum?

A
  • CCK
  • secretin
  • somatostatin
26
Q

What gut hormones are released in the pancreas?

A
  • insulin
  • glucagon
  • somatostatin
  • pancreatic polypeptide
27
Q

What gut hormones are released in the 2nd bit of the small bowel?

A
  • PYY
  • GIP (gastric inhibitory peptide)
  • GLP-1
  • GLP-2
  • oxyntomodulin
  • neurotensin
  • somatostatin
28
Q

What gut hormones are released in the large bowel?

A
  • PYY
  • GLP-1
  • oxyntomodulin
  • neurotensin
  • somatostatin
29
Q

What is gastrin?

A
  • hormone synthesised in gastric antrum and upper small intestine
  • released stimulated by AAs, peptides, gastric distension and vagus nerve (parasymp)
  • stimulates parietal cells to secrete acid
  • release inhibited when pH in stomach <3
30
Q

What is secretin?

A
  • hormone secreted by S cells in upper duodenum and jejunum
  • release stimulated by presence of acid in duodenum
  • stimulates pancreatic bicarbonate secretion
  • inhibits gastrin, acid secretion, and growth of stomach mucosa
31
Q

What is cholecystokinin?

A
  • hormone secreted by duodenal I-cells
  • release stimulated by fat and peptides in upper small bowel
  • stimulates pancreatic enzyme release (lipase, amylase, proteases)
  • delays gastric emptying
  • stimulates gallbladder contraction and relaxes sphincter of Oddi
  • hunger suppressant
32
Q

What is glucose-dependent insulinotropic peptide (GIP)?

A
  • hormones secreted by K cells in small bowel
  • release stimulated by all 3 macronutrients: glucose, AAs, fatty acids
  • stimulates release of insulin from pancreas
33
Q

What is the function of the hormone motilin?

A

increases GI motility

34
Q

What is somatostatin?

A
  • hormone secreted by D cells in stomach, intestine and pancreas
  • universal inhibitor
  • stops gastric secretion, release of gut hormones etc…
35
Q

What is glucagon-like peptide-1 (GLP-1)?

A
  • hormone secreted in small bowel from L cells
  • release stimulated by presence of glucose and fat
  • induces satiety and increases sensitivity of pancreatic beta cells to glucose
36
Q

What is pancreatic polypeptide?

A
  • hormone secreted by PP cells in pancreas
  • release stimulated by fat
  • potential role in satiety
37
Q

What is peptide YY?

A
  • hormone secreted by L cells after meal

- reduces intestinal motility, gallbladder contraction and pancreatic exocrine secretion

38
Q

Where are the neurocrines located?

A

within nerves in the gut

39
Q

What is the function of vasoactive intestinal peptide (VIP)?

A

relaxation of gut smooth muscle

40
Q

What is the function of gastrin releasing peptide (GRP)?

A

induces gastrin release

41
Q

What is the function of enkephalins?

A

increase smooth muscle tone

42
Q

What are neuroendocrine tumours?

A

proliferation of neuroendocrine cells in GI tract and pancreas

BRS Term 2 (36 decks)

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