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Physiology Part 1 > Lec 18 Control of GI function > Flashcards

Lec 18 Control of GI function Flashcards

1
Q

What are the layers of GI tract in order?

A
  • epithelium
  • lamina propria
  • muscularis mucosa
  • submucosa
  • submucosal plexus
  • circular muscle
  • myenteric plexus
  • longitudinal muscle
  • serosa
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2
Q

Where is auerbach’s plexus?

A

aka myenteric plexus

- between circular and longitudinal muscle

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3
Q

Where is meissner’s plexus?

A

aka muscosal plexus

- between submucosa and circular muscle

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4
Q

pathway of GI hormone action?

A
  • endocrine cell of GI tract secretes hormone

- -> enters portal circulation –> liver –> systemic circulation –> target cell

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5
Q

pathway of GI paracrine action?

A
  • endocrine cell of GI tract secretes –> diffuses to target cells
  • release hem transmitters into interstitial space surrounding nearby cells
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6
Q

pathway of GI neurocrine action?

A
  • neuron of GI tract secretes at action potential to target cell
  • reach target receptor on adjacent tissue
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7
Q

pathway of GI autocrine action?

A
  • type of paracrine communication, provides feedback inhibition to reduce further secretion
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8
Q

How does parasympathetic act on GI function? Where does it primarily act?

A
  • stimulates digestion via vagus
  • especially acts at esophagus and stomach
  • diminishes distally
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9
Q

What 2 parts of GI under voluntary response?

A
  • control of swallowing

- contraction of external anal sphincter

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10
Q

3 actions of parasympathetic on GI?

A
  • stimulates flow of saliva
  • stimulates peristalsis and secretion
  • stimulates release of bile
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11
Q

4 actions of sympathetic on GI?

A
  • inhibits flow of saliva
  • inhibits peristalsis and secretion
  • converts glycogen to glucose
  • secretion adrenaline/noradrenaline
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12
Q

What kind of transmitters in parasympathetic innervation of GI [pre and post ganglionic?]

A

preganglionic: ACh

postganglionic ACh or neuropeptide [peptidergic transmitters]

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13
Q

What kind of transmitters in sympathetic innervation of GI [pre and post ganglionic?]

A

preganglionic: ACh
postganglionic: NE

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14
Q

Via what nerves does parasympathetic reach GI?

A
  • vagas

- pelvic cholinergic nerves

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15
Q

Where is parasympathetic stimulation of GI mostly directed [2 places]?

A
  • esophagus + stomach

- decreased effect in distal GI tract

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16
Q

Via what nerves does sympathetic reach GI?

A
  • through splanchnic nerve

- paravertebral, celiac, superior mesenteric, and inferior mesenteric ganglia

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17
Q

Does enteric nervous system have more or fewer neurons than spinal cord?

A

more!

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18
Q

What does myenteric plexus do [2 things]? where is it located?

A
  • in between longitudinal and circular muscle layers
  • provides motor innervation to both layers
  • provides secretomotor innervation to mucosa
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19
Q

Where are cell bodies of the enteric nervous system located?

A

submucosal plexus [meissners]

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20
Q

True or false: most neurons in ENS have only 1 transmitter

A

FALSE – most neurons in ENS release more than 1 transmitter

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21
Q

What is function of NO in ENS?

A
  • primarily inhibitor neurotransmitter
  • responsible for sphincter relaxation
  • formerly called “non-adrenergic, non-cholinergic [NANC]”
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22
Q

Where are GI hormone secreting cells located?

A
  • islets of pancreas

- interspersed between mucosal cells throughout epithelium [columnar cells]

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23
Q

What are GI homrone secreting cells in the mucosa called?

A

enterochromaffin cells

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24
Q

What is the biggest endocrine organ in the body?

A

GI

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25
What are most abundant type of chemical transmitters in GI tract? What is another name for them?
- regulatory peptides | - brain gut peptides
26
What are 8 things normally secreted in GI as hormones?
- gastrin - secretin - GIP - glucagon, GLP1, GLP2 - motilin - pancreatic polypeptide - peptide YY - Ghrelin
27
What are 4 things normally secreted in GI as neuropeptides?
- Gastrin releasing peptide [GRP] - VIP - substance P; tachykinin - neuropeptide Y
28
What are 2 things secreted in GI as hormones or neuropeptides or paracrine?
- CCK | - somatostatin
29
Where is gastrin released from? What stimulates/inhibits its release? What type of release/action?
- released from G cells in antrum [mostly] and duodenum - stimulated by high pH and AA - inhibited by gastric acid [via somatostatin + secretin] - mainly as hormone
30
What are 2 actions of gastrin?
1. promotes gastric acid secretion from parietal cells 2. acts as growth factor for ECL [enterochromaffin like cells] - -> tells ECL to make histamine = indirect parietal stimulation - -> in excess can lead to tumors
31
What does gastrin bind to?
CCK receptor
32
What 3 things act on parietal cell to induce acid secretion? And where do they bind?
Gastrin --> CCK receptor Histamine --> H2 receptor ACh --> M3 receptor
33
What are direct and indirect pathways that gastrin activates parietal cell acid secretion?
direct: gastrin activates parietal cells to secrete acid indirect: gastrin tells ECL cells to grow and secrete histamine --> histamine activates parietal to secrete acid
34
What stimulates CCK release?
- amino acids and fatty acids
35
Where is cholecytokinin released from? what type of release
- I cells in proximal small intestine | - mainly acts as hormone
36
What family of proteins is gastrin in?
gastrin/CCK family
37
what family of proteins is CCK in?
gastrin/CCK family
38
What are 2 main actions of CCK?
- gallbladder contraction - stimulates pancreatic enzyme secretion [and HCO3] also less important: slows gastric emptying, induces satiety
39
What is secretin secreted from? where is it released from?
- S cells in proximal small intestine
40
What stimulates secretion of secretin?
- gastric acid [pH < 4.5] | - other acid [fatty acid, bile acid, spicy food, EtOH]
41
What are the 3 actions of secretin?
- induces secretion HCO3 from pancreas/duodenum/bile duct = MAIN FUNCTION also - inhibits gastrin release [and thus inhibits gastrin] - inhibits intestinal motility
42
What hormone opposes the action of gastrin?
secretin
43
What mech is secretin normally secreted?
as a hormone
44
What family is secretin part of?
secretin/VIP/glucagon/GIP family
45
What is vasoactive intestinal peptide [VIP]?
A neuromediator from enteric nervous system
46
What are 3 possible actions of VIP?
- stimulate epithelial cell contraction - stimulate smooth muscle [sphincter] relaxation - VIP-secreting tumors
47
What are symptoms of a VIP-oma?
- watery diarrhea - hypokalemia [low K] - achlorhydria [low gastric acid]
48
What is glucagon? Where is it made
hormone made by: - pancreatic alpha cells - cells of small intestine/colon [L cells]
49
what is proglucagon? where is it broken down into which things?
- precursor gene transcript - in pancreas: processed into glucagon - in small intestine: processed to GLP1/2 [glucagon-like peptides]
50
What is function of glucagon?
regulate glucose homeostasis [with GLP-1]
51
What is function of GLP-1?
regulate glucose homeostasis [with glucagon]
52
What is function of GLP-2?
acts as intestinal growth factor, helps maintain GI mucosal mass
53
What other 3 things are in same family as glucagon?
secretin/VIP/glucagon/GIP family
54
What is glucose-dependent insulinotropic polypetide [GIP]? Where is it released from
- a hormone | - released from small intestine [k cells]
55
What stimulates GIP release?
- released in response to hyperglycemia
56
What is action of GIP?
- stimulates pancreatic B cells to secrete insulin
57
What x things are in the tachykinin family of proteins?
- substance P | - Gastrin releasing peptide [GRP]
58
what family is substance P? By what 2 mech does substance P act?
- Tachykinin family - acts by neurocrine and paracrine - in CNS/PNS
59
What are actions of substance P?
- pain sensation [PRIMARY function] - pro-inflammation - inhibition of: somatostatin, biliary secretion
60
What two things does substance P inhibit?
- somatostatin | - biliary secretion
61
What family is gastrin releasing peptide [GRP]? What is normal mech of release?
- part of tachykinin family | - neurocrine, released by post-ganglionic parasympathetic
62
What 2 actions of GRP?
- mediates vagal release of gastrin | - stimulates pancreatic secretion and GI motility
63
What is motilin? where is it released from? What family of proteins?
- hormone - made in duodenum - motilin family of proteins
64
What are actions of motilin?
- binds receptors on smooth muscle through gut = pro-motility - increases phase III contraction of MMC [increases peristalsis]
65
What drug is motilin agonist?
erythromycin
66
What family of protein is grhelin? Where is it made?
- part of motilin family | - made in gastric fundus [PD1 cells]
67
What proteins are in motlin family?
- motilin | - ghrelin
68
Action of ghrelin?
- increases food intake | - high levels during fasting, low levels when fed
69
What is Prader-Willi syndrome?
extra high ghrelin [so always hungry]
70
What family is pancreatic polypeptide [PP]? Where is it released from?
- pancreatic polypeptide family | - released from pancreatic islet cells [PP cells]
71
What stimulates pancreatic polypeptide release?
- vagus - amino and fatty acids - gastrin/CCK - secretin
72
What are functions of pancreatic polypeptide?
MAINLY: inhibit pancreatic exocrine secretion also - gall bladder contraction - gut motility
73
What family is peptide YY? WHere is it released from?
- pancreatic polypeptide family | - released from distal small intestine [L cells]
74
What stimulates PYY secretion?
meals, fat, bile acids
75
What are the actions of PYY?
- ileal break --> slow small intestine motility to increase absorption time - inhibits pancreatic and gastric acid secretion
76
What is neuropeptide YY [NPY]
- neurocrine homologue of PYY - found in CNS/PNS - binds sam receptors as PYY
77
What is function of NPY?
- mimics PYY [ileal break, inhibition pancreatic/gastric acid secretion] - also stimulates appetite
78
What are 4 inhibitory signals of gastric emptying
- low pH --> inhibits secretin - AA and fatty A --> inhibit cholecystokinin - osmolality --> inhibits vagal afferents - carbohydrates --> inhibit PYY
79
Where is somatostatin made? [KNOW THIS CELL NAME]
- D cells in antrum | - also less importantly: by cells in small intestine, pancreatic islets, enteric neurons
80
What 3 things stimulate somatostatin release?
- gastric acid in lumen - diet [protein, fat, glucose] - muscarinic stimulation
81
What inhibits somatostatin?
high pH
82
What are the major actions of somatostatin?
GLOBAL INHIBITOR - inhibits gastric acid [via G and parietal cells] - inhibits pancreatic secretion - reduces bile flow - slows motility - reduces splanchnic blood flow

Physiology Part 1 (37 decks)

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