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Kaplan Physio > GI > Flashcards

GI Flashcards

1
Q

lamina propria

A

layer of CT that contains glands, hormone-containing cells, LN and capillaries

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2
Q

submucosa

A
  • layer of CT that contains glands, large bv, and lymphatics
  • outermost region has nerve net called meissner’s plexus
  • Meissner’s plexus = part of enteric nervous system; involved in secretory activity
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3
Q

an increase in sympathetic activity has what effects on the GI tract

A
  • decrease motility, decrease secretion (through NE)

- increase constriction of sphincters (through NE)

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4
Q

an increase in parasympathetic activity has what effects on the GI tract

A
  • promotes digestive and absorptive processes:
  • incresaed motility and secretions (through ACh)
  • increased gastrin (GRP stimulates G cells)
  • decreased constriction of sphincters (through VIP = inhibitory parasympathetic transmitter)
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5
Q

nerve gas has what effect on GI tract

A

nerve gas increases GI and bronchial secretions

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6
Q

Electrical activity in GI Smooth muscle

A
  • resting membrane potential = close to depolarization (-45 to -60)
  • oscillation of membrane potential generated by interstitial cells of Cajal that act as pacemakers (creates the intrinsic motor activity)
  • this is called slow waves or basic electrical rhythm (always some basal motor activity in the GI tract)
  • slow waves create low-level contractions
  • if threshold is reached, generates AP
  • AP are generated by opening of slow channels that allow entry of BOTH Na and Ca
  • AP strengthen the contractions
  • duodenum contracts the most often
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7
Q

Response to stretch in the GI tract

A
  • stretch produces a contractile response
  • ex) stomach distention stimulates ACh and increased parasympathetic activity (increases stomach motility)
  • overload of the duodenum decreases stomach motility
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8
Q

Secretin

  • source
  • stimulus
  • effect
A
  • source: S cells lining duodenum
  • stimulus: acid entering duodenum
  • inhibits stomach motility and secretion
  • stimulates fluid secretion (HCO3-) from the pancreas
    (neutralizes stomach acid entering duodenum)
  • stimulates insulin release (pancreas)
  • no effect on gallbladder
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9
Q

anticholinergic medications have what effect on GI motility

A

slow GI motility

  • ex) atropine or TCA
  • however, atropine alone cannot slow the stomach, bc GRP bypasses ACh
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10
Q

Cholecystokinin (CCK)

  • source
  • stimulus
  • effect
A
  • source: cells lining duodenum
  • stimulus: fat and AA entering duodenum
  • inhibits stomach emptying (increase the degree of pyloric constriction)
  • stimulates enzyme secretion from pancreas
  • stimulates insulin release (from pancreas)
  • stimulates Gallbladder contraction and relaxation of sphincter of Oddi for bile into the duodenum
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11
Q

Gastrin

  • source
  • stimulus
  • effect
A
  • source: G cells of stomach, stimulate stomach distention
  • Source: Pyloric Antrum, stimulate parasym peptides (GRP)
  • source: duodenum, stomach acid inhibits (negative feedback)
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12
Q

Gastric Inhibitory Peptide (GIP); Glucagon-like peptide (GLP)

  • source
  • stimulus
  • effect
A
  • source: duodenum
  • stimulus: fat, carb, AA
  • inhibits stomach motility and secretion
  • effect on gallbladder:
    1. GIP increases insulin
    2. GLP decreases glucagon
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13
Q

In swallowing, how is relaxation of the LES triggered?

A

VIP acts as an inhibitory transmitter of the myogenic smooth muscle of the LES

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14
Q

Difficulty initiating swallowing

A

= oropharyngeal dysphagia, usually neural in origin

- bc swallowing is a reflex controlled from the brain stem

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15
Q

Stomach emptying in order from fastest (1) to slowest (4)

A
  1. liquids
  2. carb
  3. protein
  4. fat
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16
Q

ileocecal sphincter

A
  • valve btw SI and LI
  • distention of ileum creates a muscular wave that relaxes sphincter
  • distension of colon creates a nervous reflex to constrict the sphincter
17
Q

motilin

A
  • SI hormone
  • stimulates the migrating myoelectric complex (propulsive movement repeated every 90-120 mins during fasting that moves from stomach to colon)
  • this movement prevents the back flow of bacteria from the colon into the ileum and its subsequent overgrowth in the distal ileum
18
Q

composition of salivary secretions

A
  • low in Na+ and Cl-, bc reabsorption
  • high in K+, HCO3- , bc of secretion (pH = 8)
  • salivary fluid is HYPOtonic bc of reabsorption of NaCl and impermeability of ducts to water
  • alpha-amylase (ptyalin): secreted in the active form and begins the digestion of carbs
  • mucus, glycoprotein
  • immunoglobulins and lysozymes
  • regulated via parasympathetic input
19
Q

Parietal cells

A
  • secrete HCL
  • intrinsic factor combines w Vit B12 and is reabsorbed in the distal ileum
  • this is the only substance secreted by the stomach that is required for survival
  • it is released by the same stimuli that release HCL
20
Q

Chief Cells

A
  • pepsinogen is converted to pepsin by H+
  • active pepsin continues the process
  • only active in the acid pH medium of the stomach
  • begins the digestion of protein but is NOT essential for life
  • Pepsin is secreted by chief cells
21
Q

Mucous Neck Cells

A
  • secrete the protective mucous, HCO3 combination
  • the epithelial cells that cover the gastric mucosa secrete a highly viscous alkaline fluid (mucin + HCO3) that protects the stomach lining from the acid
  • NSAID decrease the secretion of mucin and HCO3
22
Q

3 natural substances that stimulate parietal cells

A
  • gastric acid secretion via a H/K-ATPase pump
    1. ACh; release is stimulated by sight/smell of food and reflexly in response to stomach distention (vasovagal reflex)
    2. locally released histamine; stimulated by ACh and gastrin
    3. hormone gastrin; stimulated by release of GRP
  • as stomach pH falls, SOMATOSTATIN is released, and inhibits gastrin and reduces acid secretion (feedback regulation of acid secretion)
23
Q

Diarrhea

A
  • a loss of isotonic fluid that is high in HCO3 and K+

- EXCEPT in infants, where it can be HYPOtonic

24
Q

pepsinogen is converted to pepsin by

A
  • H+
  • only active in the acid pH medium of the stomach
  • begins the digestion of protein but is NOT essential for life
  • Pepsin is secreted by chief cells
25
Q

Carbonic anhydrase

A
  • converts CO2 to H+ and HCO3
26
Q

Compared to extracellular fluid, gastric secretions

A
  • high in H+, K+, Cl-
  • low in Na+
  • the greater the secretion rate, the higher the H+ and lower the Na+
27
Q

Trypsin inhibitor

A
  • protein present in pancreatic secretions

- prevents activation of the proteases within the pancreas

28
Q

how do you get active trypsin

A
  • trypsinogen is secreted by the pancreas and activated to trypsin by enterokinase (aka enteropeptidase)
  • enterokinase = enzyme secreted by the lining of the SI. NOT A BRUSH BORDER ENZYME.
  • trypsin then goes on to activate the other proteases (i.e. chymotrypsinogen and procarboxypeptidase)
29
Q

stercobilin

A
  • produced from metabolism of bilirubin by intestinal bacteria
  • gives stool its brown color
30
Q

how does cholera produce diarrhea

A
  • cholera toxin binds and activates Gs, increases cAMP

- cAMP opens luminal Cl- channels, causing massive secretory diarrhea

31
Q

Where are bile salts reabsorbed

A
  • distal ileum ONLY
  • electrolytes and water (but not bile pigments or bile salts) can be absorbed from the gall bladder lumen
  • distal ileum also absorbs intrinsic factor-Vit B12 complex
32
Q

lipid digestion requires

A
  • bile micelles and pancreatic lipase

- end products absorbed include 2-monoglycerides and FA

33
Q

digestion of carbs requires

A
  • pancreatic amylases and the small intestinal brush border enzymes
  • end products absorbed: monosaccharides
  • disaccharides can’t be absorbed from the SI
34
Q

digestion of protein requires

A

pancreatic proteases (must be activated by enterokinase/enteropeptidase and the intestinal brush border enzymes)

35
Q

Absorption in the colon

A
  • net absorption of water and electrolytes
  • influenced by aldosterone, but has a net secretion of HCO3 and K
  • doesn’t have digestive enzymes or transporters to absorb products of digestion

Kaplan Physio (4 decks)

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