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Physiology - GI > Functions and Regulations of GI > Flashcards

Functions and Regulations of GI Flashcards

1
Q

parts of the GI

A

tracts and glands

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2
Q

what does the GI system do

A

digestion, absorption of electrolytes and water, elimination of waste products

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3
Q

conduit in the GI system

A

esophagus

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4
Q

contains chyme

A

stomach

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5
Q

most of digestion is done where

A

small intestine

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6
Q

bile storage

A

gall bladder

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7
Q

what does the pancreas (exokrine) do

A

has digestive enzymes and HCO3- as H+ buffer

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8
Q

name the glands of the GI system

A

pancreas, liver, salivary glands, gall bladder

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9
Q

what does the liver do

A

bile (excretion, lipid digestion), metabolism, detoxification

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10
Q

difference between physical and chemical alteration of food

A

physical - mastication

chemical - involves breakdown of food with enzymes

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11
Q

difference between secretion and absorption

A

secretion - from ECF to lumen

absorption - lumen to ECF

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12
Q

what is motility

A
  • movement and mixing
  • contraction of smooth muscles
  • requires ANS, hormones, and paracrines
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13
Q

4 layers of the GI tract

A

mucosa, submucosa, muscularis propria, serosa or adventitia

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14
Q

what are each layer of the GI tract made up of

A

mucosa - epithelium, lamina propria, muscularis mucosa
submucosa - meissner’s (submucosal) plexus
muscularis propria - circular muscle, (Auerbach’s myenteric plexus), longitudinal muscle

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15
Q

significance in the muscularis propria layers of the Auerbach’s plexus being in between the circular and longitudinal muscle

A

has to deal with motility

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16
Q

force of contraction in the smooth muscle of GI is the function of what?

A

calcium entry into the cell > 10^-7M

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17
Q

explain how a rise in intracellular calcium causes contraction of smooth muscle

A
  • once an increase in intracellular calcium, calcium binds to calmodulin
  • calmodulin activates myosin light chain kinase
  • myosin light chain kinase phosphorylates myosin to myosin-Pi
  • phosphorylated myosin interacts with actin and ATP and causes a contraction
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18
Q

how does the smooth muscle relax

A
  • when the intracellular calcium drops, calcium and calmodulin disassociate
  • the myosin light chain kinase becomes inactivated
  • myosin light chain phosphatase dephosphorylates myosin-Pi causing relaxation
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19
Q

what does the contraction of the smooth muscle result in

A

peristalsis - propels food along tract
segmentation - mixes food
migration motor complex - cleans out gut in fasted state

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20
Q

what causes rumbling of the stomach

A

migration motor complex cleaning out the gut in the fasted state

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21
Q

what is GI effector 1

A

smooth muscle

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22
Q

what is GI effector 11

A

epithelia

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23
Q

nature of the cells in the epithelia

A

endocrine and secrete mucous

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24
Q

characteristics of epithelia

A

single layer that is 1cm thick, highly folded to increase surface area for absorption, invaginated for glands that secrete

25
Q

mode of transcellular and paracellular passage

A

transcellular - passive or active

paracellular - passive

26
Q

is the apical surface of a cell closer to lumen or to the blood

A

closer to the lumen

27
Q

characteristics of tight epithelia and an example

A
  • has high resistance
  • do not want water going through
  • highly regulated
  • significant ionic gradients and transepithelial voltage

ex: distal colon

28
Q

characteristics of leaky epithelia and an example

A
  • low resistance
  • water can pass through (high permeability)
  • smaller ionic and voltage gradient

ex: small intestine

29
Q

how are GI effector regulated

A

innervation, endocrine, paracrine

30
Q

what controls absorption and secretion

A

meissner’s submucosal plexus

31
Q

how to remember meissner’s plexus and myenteric plexus and what they do

A
  • meissner in the submucosal –> mucous is wet –> secretion and absorption; glandular epithelium, intestine endocrine cells, submucosal blood vessels
  • myenteric - M for motility and between those circular and longitudinal muscles
32
Q

parasympathetic or sympathetic - which is most important in the GI and what does it do?

A
  • parasympathetic (think rest and digest)
  • increased motility and secretion
  • distension, satiety, and nausea
33
Q

what neurotransmitter does parasympathetic use in the GI

A

acetylcholine

34
Q

role of sympathetics in the GI and its neurotransmitter used

A
  • antagonizes parasympathetic
  • contracts sphincter and vasoconstriction
  • pain and nausea
  • uses norepinephrine
35
Q

what is the issue in Hirschsprung disease

A
  • massive distension of proximal colon due to absent meissner submucosal and myenteric plexus
  • aganglionic portion of large bowel
36
Q

are all peptides hormones or are all hormones peptides

A

all hormones are peptides

37
Q

two hormones released in the stomach

A

ghrelin and gastrin

38
Q

hormones released in the duodenum

A

CCK, secretin, GIP, motilin

39
Q

where is GLP-1 released

A

jejunum

40
Q

another name for gastrin, its target, its action

A
  • G cells
  • target: enterochromaffin like cells (ECL) and parietal cells
  • action: stimulates gastric acid and increases gastric mucosal growth
41
Q

what increases and decreases secretion of gastrin

A
  • increases: AA in stomach, distension, gastrin releasing peptide, Ach
  • decreases - somatostatin and acid with pH less than 1.5
42
Q

another name for CCK, its target, its action

A

-CCK is short for cholecystokinin aka I cell
-target: endocrine cells of SI and neurons of GIT
-action: motility: gall bladder, GIT, delivery of chyme from stomach
pancreatic secretions: enzymatic and increases satiety

43
Q

what increases and decreases secretion of CCK

A

increases: FA and AA in SI, distension
decreases: somatostatin

44
Q

another name for secretin, its target, its action

A
  • S cell
  • target: pancreas and stomach
  • action: increase HCO3- secretion by pancreas, decreases gastric acid, neutralizes acid delivered to duodenum, allows intestinal enzymes to operate at optimum pH
45
Q

what increases and decreases secretion of secretin

A
  • increases: acid in SI

- decreases: somatostatin

46
Q

actions of ghrelin and what increases is secretion

A
  • X cell
  • stimulates food intakes, GH release
  • increased by hypoglycemia and low bodyweight
47
Q

target and action of motilin and what increases its secretion

A
  • M cell
  • target: smooth muscle of antrum and duodenum
  • action: stimulates migrating motor complex
  • increased secretion when fasting - periodically every 1-2 hours
48
Q

what are the incretins? examples of incretins and another name for each one named

A
  • incretins are hormones released that stimulated decrease in blood glucose levels
  • ex: GIP (K cell) and GLP-1 (L cell)
49
Q

target, action, +secretion of GIP aka K cell

A
  • target: beta cells of pancreas
  • action: increase insulin secretion
  • +secretion: glucose, FA, and AA in SI
50
Q

target, action, +secretion of GLP-1 aka L cell

A
  • target: Pancreas
  • action: increase insulin secretion and glucagon release
  • +secretion: carbohydrates in lumen
51
Q

stimulates gastric acid release

A

histamine (ECL cell and mast cells)

52
Q

stimulates gastric acid release

A

histamine (ECL cell and mast cells)

53
Q

potent inhibitor

A

somatostatin

54
Q
  • pancreatic/ gastric secretion
  • motility
  • gall bladder contraction
  • nutrient absorption
  • vasoconstrictor
A

somatostatin (D cell)

55
Q
  • gut motility and secretion

- stimulus: distention of GI wall

A

serotonin (ECL cell)

56
Q

what is happening in cephalic phase

A
  • 40% of time in phase

- thought, smell, sight, taste and swallowing of food

57
Q

what is happening in gastric phase

A
  • 50% of time in phase

- what is happening in the stomach

58
Q

what is happening in the intestinal phase

A
  • 10% of time in phase

- what’s happening in the intestine

Physiology - GI (6 decks)

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