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GI Physiology Flashcards

1
Q

GI slow waves vs spikes?

A

Slow waves -rhythmic contractions, do not produce action potentials, sodium entry
Spikes - true action potential, usually happens during peak of slow waves,calcium entry

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2
Q

Pacemaker of GI smooth muscle is called

A

Interstitial Cells of Cajal

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3
Q

The following stimuli depolarize or hyperpolarize?

  1. stretch
  2. acetylcholine
  3. norepinephrine
A

1 and 2 - depolarixe

3. hyperpolarize

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4
Q

Outer neural GI plexus lying between longitudinal and circular muscle layers

A

Auerbach’s plexus or myenteric plexus

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5
Q

Inner neural GI plexus in the submucosa

A

Meissner’s plexus or submucosal plexus

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6
Q

Difference in f(x) of GI plexus

A

Auerbach - GI movement

Meissner - secretion and blood flow

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7
Q

Identify site of secretion, stimuli for secretion, and action of gastrin?

A

secreted by G cells in antrum of stomach,
stimuli - distension, protein, gastrin-releasing peptide ( from vagus)
action - gastric acid secretion, mucosal growth

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8
Q

Identify site of secretion, stimuli for secretion, and action of cholecystokinin?

A

secreted by I cells in duodenum and jejunum
stimuli - fat, monoglycerides
action - contract gallbladder, inhibit stomach contraction moderately (allow time for fat digestion), inhibit appetite

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9
Q

Identify site of secretion, stimuli for secretion, and action of secretin?

A

secreted by S cells in duodenum
stimuli - gastric acid
action - promote pancreatic secretion of HCO3-

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10
Q

Identify site of secretion, stimuli for secretion, and action of glucose-dependent insulinotropic peptide (gastric inhibitoruy peptide?

A

secreteed by K cells in duodenum and jejunum
stimuli - fat, amino acid, carbs
action - decreasegastric emptying, stimulate insulin secretion

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11
Q

Identify site of secretion, stimuli for secretion, and action of motilin

A

secreted by M cellsof duodenum and jejunum
stimuli -fasting
action - increase GI motility

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12
Q

First GI hormone to be discovered?

A

Secretin

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13
Q

Motilin is released cyclically and stimulates waves of GI motility (interdigestive myoelectric complexes) every how long during fasting?

A

90 minutes

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14
Q

Stimuli for peristalsis

A

Gut distension, myenteric plexus activity

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15
Q

Events in peristalsis

A

Distension initiates peristalsis
contractile ring begins on orad side, and is polarized in the anal direction toward distended segment
gut downstream relaxes
Food is pushed

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16
Q

mixing movements occur when?

A

Peristaltic movement is blocked by sphincter

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17
Q

Which materials from the splanchnic veins can bypass the liver? Where does it pass

A

Fats absorbed- to lymphatics and thoracic duct

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18
Q

Effect of the following on vasocontriction of splanchnic circulation

  1. Gastric Hormones
  2. VIP
  3. Oxygen
  4. Kinins (bradykinin, kallidin)
  5. Adenosine
A

1 - Dilate

  1. Dilate (vasoactive intestinal peptide)
  2. constrict. Low o2 dilates,signifieshigh gut activity
  3. dilate
  4. dilate. adenosine is assoc with decreased o2
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19
Q

3 stages of swallowing

A 
Voluntary stage
Pharyngeal stage (inv)
Esophageal stage (inv)
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20
Q

Structure which prevents large objects or poorly chewed bolus from being swallowed?

A

Palatopharyngeal folds (approximate and form slit when swallowing)

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21
Q

Movements of the the larynx during swallowing?

A

Vocal cords approximate
larynx pulled upward and anteriorly
epiglottis closes

22
Q

Primary vs Secondary peristalsis in the esophagus

A

Primary - initiated from pharynx after voluntary phase

secondary - food in esophagus causes distension which initiates peristaltic wave

23
Q

Function of vagovagal reflex in stomach

A

Distension –> relaxing of wall –> expands stomach

24
Q

Retropulsion in stomach mechanism

A

Constrictor rings in antrum contract intensely from peristaltic action potential, but pylorus is closed, so food goes back to body

25
Two gastric factors promoting emptying and mechanism
1. Distension - increased volume stretches stomach wall, which elicit myenteric reflex that inhibit pyloric sphincter 2. Gastrin - enhances pyloric pump
26
Effect of the presence of the ff in duodenum on gastric emptying and logic 1. Distension 2. Acidity 3. Breakdown products of proteins 4. Hypotonic 5. Hypertonic
All inhibitory 1, 2, and 3 signify excessive unprocessed chyme, to allow duodenum to digest it properly 4 and 5 are regulatory mechanisms
27
What is the stimulus for release of inhibitory peptides in duodenum?
Mostly fat (CCK)
28
Peristalsis is faster in proximal or distal intestine?
Proximal
29
Which of the ff inhibits and which enhance small intestinal motility gastrin, secretin, CCK, motilin, serotonin, insulin, glucagon
Enhance - gastrin, CCK, insulin, motilin, serotonin | Inhibit - secretin, glucagon
30
What is peristaltic rush
Irritation of intestinal mucosa causes powerful and rapid peristalsis - cleaning intestine through diarrhea
31
``` Effect of the ff on ileocecal valve emptying 1. Fluidity of ileal contents 2, Ileal pressure and volume 3. Cecal Volume 4. Cecal irritant, like appendicitis 5. Gastroileal reflex ```
1, 2, and 5 increase | 3 and 4 decrease
32
Sympathetic and parasympathethic effect on GI tract glandular secretion
Para - increase Sympa only - slight increase Para with sympa - decrease (by vasoconstriction)
33
Average daily secretion of saliva
1000 mL
34
Content of salivary secretion (type, enzyme, and ions)
Serous secretion - ptyalin (alpha amylase) Mucous - mucin Ions - K and HCO3-
35
Which salivary glands secrete which
Parotid - mostly serous Submandibular and sublingual - mixed Buccal - mostlt mucous
36
Mechanism of ion exchange in salivary gland
1. Acini secrete ptyalin, mucin in solution with ECF 2. Na is actively reabsorbed and K is actively secreted in ducts 3. More positive ions are reabsorbed, creating electronegativity which causes Cl passive reavsorption 4. Ductal epith secretes bicarbonate in exchange for Cl, plus actively
37
Two bactericidal substances secreted in saliva
Thiocyanate ion | Lysozyme
38
Secretions from gastric oxyntic gland (name cell amd susbtance)
Mucous neck cell - mucous Peptic or chief cells - pepsinogen Oxyntic cell or parietal cell - HCl and intrinsic factor Enterochromaffin-like cell (ECL cell) - histamine
39
Secretions from pyloric glands of stomach
Gastrin and mucus
40
Mechanism of HCl secretion
H ions 1. Water is hydrolyzed to H+ and OH- 2. H+ secreted K+ absorbed in H-K atpase in lumen 3. Basolateral Na K atpase K inside cell Na outside to ecf, then K leaks out to lumen, providing power for HK atpase. Low intracellular Na allows Na absorption from lumen Cl 1. Water combines with CO2 to form H+ and HCO3- 2. Bicarb - Cl pump in basolateral pumps Cl into cell and bicarb to ECF 3. Cl is secreted through chloride channels High ion concentration in lumen then alllows osmosis
41
Effect of gastrin, ach, and histamine on gastric secretion
Acetylcholine - increase pepsinogen, Hcl, and mucus (all secretion) Histamine and gastrin - increase acid
42
What activates pepsinogen
HCl
43
Function of intrinsic factor from parietal cell
For absorption of Vit B12 in ileum
44
Contents of pancreatic juice
Bicarbonate Trypsin, chymotrypsin, carboxypolypeptidase Pancreatic amylase Pancreatic lipase, cholesterol esterase, phospholipase
45
What activates inactive enzymes of protein digestion
Trypsinogen by enterokinase and activated trypsin Others by activated trypsin
46
Mechanism of NaHCO3 secretion in pancreas
1. Na-HCO3 co-transport from ECF to acinar cell 2. CO2 diffusion + H2O -> HCO3- and H+ 3. H+ exits and Na enters in Na-H channel in basolateral 4. HCO3 exits and Cl enters in luminal channel 5. Na exits in luminal border 6. Solute exerts osmotic pressure and drags water
47
Function of Ach, CCK and Secretin on pancreatic secretion
Ach and CCK stimulare acinar cells to secrete enzymes Secretin stimulate secretion of NaHCO3 solution and propels enzymes to duodenum
48
Difference in liver bile and GB bile in terms of concentration of components and ikns
Liver - more water, Na, Cl, HCO3 (similar to usual secretory ducts) GB - more concentrated. More bile salt, bilirubin, cholesterol, lecithin, fatty acids, as well as K, Ca
49
Function of brunners gland and what regulates it
Secrete mucus in duodenum Responds to duodenal irritants, vagal stimulation, secretin
50
Cells found in crypts of lieberkuhn and function
Goblet cell - secrete mucous | Enterocyte - secrete water, HCO3- and Cl- which lubricates chyme, then reabsorb them along with chyme
51
Digestive enzymes in small intestine secretion
Peptidases, sucrase, maltase, lactase, isomaltase, intestinal lipase
52
Secretions of the large intestine
Mucus ONLY. No enzymes

PLE Physiology (7 decks)

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