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PLE Physiology > GI Physiology > Flashcards

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
Q

Two gastric factors promoting emptying and mechanism

A
  1. Distension - increased volume stretches stomach wall, which elicit myenteric reflex that inhibit pyloric sphincter
  2. Gastrin - enhances pyloric pump
26
Q

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
A

All inhibitory

1, 2, and 3 signify excessive unprocessed chyme, to allow duodenum to digest it properly
4 and 5 are regulatory mechanisms

27
Q

What is the stimulus for release of inhibitory peptides in duodenum?

A

Mostly fat (CCK)

28
Q

Peristalsis is faster in proximal or distal intestine?

A

Proximal

29
Q

Which of the ff inhibits and which enhance small intestinal motility
gastrin, secretin, CCK, motilin, serotonin, insulin, glucagon

A

Enhance - gastrin, CCK, insulin, motilin, serotonin

Inhibit - secretin, glucagon

30
Q

What is peristaltic rush

A

Irritation of intestinal mucosa causes powerful and rapid peristalsis - cleaning intestine through diarrhea

31
Q 
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
A

1, 2, and 5 increase

3 and 4 decrease

32
Q

Sympathetic and parasympathethic effect on GI tract glandular secretion

A

Para - increase
Sympa only - slight increase
Para with sympa - decrease (by vasoconstriction)

33
Q

Average daily secretion of saliva

A

1000 mL

34
Q

Content of salivary secretion (type, enzyme, and ions)

A

Serous secretion - ptyalin (alpha amylase)
Mucous - mucin

Ions - K and HCO3-

35
Q

Which salivary glands secrete which

A

Parotid - mostly serous
Submandibular and sublingual - mixed
Buccal - mostlt mucous

36
Q

Mechanism of ion exchange in salivary gland

A
  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
Q

Two bactericidal substances secreted in saliva

A

Thiocyanate ion

Lysozyme

38
Q

Secretions from gastric oxyntic gland (name cell amd susbtance)

A

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
Q

Secretions from pyloric glands of stomach

A

Gastrin and mucus

40
Q

Mechanism of HCl secretion

A

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
Q

Effect of gastrin, ach, and histamine on gastric secretion

A

Acetylcholine - increase pepsinogen, Hcl, and mucus (all secretion)
Histamine and gastrin - increase acid

42
Q

What activates pepsinogen

A

HCl

43
Q

Function of intrinsic factor from parietal cell

A

For absorption of Vit B12 in ileum

44
Q

Contents of pancreatic juice

A

Bicarbonate
Trypsin, chymotrypsin, carboxypolypeptidase
Pancreatic amylase
Pancreatic lipase, cholesterol esterase, phospholipase

45
Q

What activates inactive enzymes of protein digestion

A

Trypsinogen by enterokinase and activated trypsin

Others by activated trypsin

46
Q

Mechanism of NaHCO3 secretion in pancreas

A
  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
Q

Function of Ach, CCK and Secretin on pancreatic secretion

A

Ach and CCK stimulare acinar cells to secrete enzymes

Secretin stimulate secretion of NaHCO3 solution and propels enzymes to duodenum

48
Q

Difference in liver bile and GB bile in terms of concentration of components and ikns

A

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
Q

Function of brunners gland and what regulates it

A

Secrete mucus in duodenum

Responds to duodenal irritants, vagal stimulation, secretin

50
Q

Cells found in crypts of lieberkuhn and function

A

Goblet cell - secrete mucous

Enterocyte - secrete water, HCO3- and Cl- which lubricates chyme, then reabsorb them along with chyme

51
Q

Digestive enzymes in small intestine secretion

A

Peptidases, sucrase, maltase, lactase, isomaltase, intestinal lipase

52
Q

Secretions of the large intestine

A

Mucus ONLY. No enzymes

PLE Physiology (7 decks)

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