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Human Physiology > GI Physiology > Flashcards

GI Physiology Flashcards

[from BRS physiology]

1
Q

Meissner’s plexus

A

submucosal plexus, primarily conrtols the secretion and blood flow

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2
Q

Parasympathetics on the GI tract

A

usually excitatory, carried via vagus and pelvic nerves

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3
Q

Vagus nerve- GI organs

A

Esophagus, Stomach, Pancreas and upper large intestine

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4
Q

Pelvic Nerve - GI organs

A

lower large intestine, rectum and anus

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5
Q

Sympathetics on the GI tract

A

inhibitory

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6
Q

Auerbach’s plexus

A

Myenteric plexus, controls motility of GI smooth muscle

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7
Q

G cells

A

in antrum of stomach, secrete gastrin in response to a meal

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8
Q

Actions of gastrin

A

increases H+ from parietal cells

stimulates gastric mucosal growth

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9
Q

Most important stimuli for gastrin secretion

A

phenylalanine and tryptophan

others: distention of stomach, vagal stimulation mediated by GRP

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10
Q

gastrin inhibitors

A

H+ in stomach lumen (negative feedback)

somatostatin

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11
Q

gastrin is secreted by non-beta cell tumors of pancreas

A

Zollinger-Ellison Syndrome

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12
Q

Peptide that is homologous to gastrin

A

CCK

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13
Q

Actions of CCK

A

1) contract GB and relaxes sphincter of Oddi
2) pancreatic enzyme secretion
3) growth of exocrine pancreas
4) potentiates HCO3- from pancreas
5) inhibits gastric emptying

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14
Q

I cells of duodenal and jejunal mucosa

A

secrete CCK

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15
Q

Stimuli for CCK

A

small peptides, AA, FAs and monoglycerides

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16
Q

homologous to glucagon

A

secretin

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17
Q

Actions of secretin

A

stim panc HCO3- secretion and increase exocrine pancreatic growth
increase bile production
inhibits H+ from parietal cells

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18
Q

S cells

A

In duodenum, Secrete secretin in response to H+ and FAs in duodenum

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19
Q

Actions of GIP

A

Insulin release in response to ORAL glucose

inhibits H+ secretion

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20
Q

hormone secreted in response to carbs, fats and protien

A

GIP

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21
Q

Somatostatin

A

secreted by cells throughtout the GI tract in response to H+ in lumen
inhibits release of ALL GI hormones
inhibits gastric H+ secretion

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22
Q

Histamine

A

Secreted by mast cells of the gastric mucosa

increases gastric H+ secretion directly and potentiating gastrin and vagal stimulation

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23
Q

VIP

A

relaxes the lower esophageal sphincter

stimulates the pancreatic HCO3- secretion and inhibits gastric H+ secretion

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24
Q

secreted by pancreatic islet cell tumors

A

VIP

presumed to mediate pancreatic cholera

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25
Q

Bombesin

A

GRP, release from vagus nerves that innervate the G cells

stim gastrin release from G cells

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26
Q

Stimulate the contraction of GI smooth muscle, particularly the LES, pyloric and ileocecal sphincter
Inhibit intestinal secretion

A

Enkephalins

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27
Q

Opiate use in GI tract

A

Tx diarrhea

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28
Q

Tonic contractions

A

LES, orad stomach, ileocecal and internal anal sphincter

always closed unless stimulated to open

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29
Q

Phasic contraction

A

esophagus, stomach, gastric antrum, small intestine. contract and relax periodically

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30
Q

oscillating membrane potentials inherent to smooth muscle of GI tract

A

Slow waves

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31
Q

Pacemaker of GI tract

A

interstitial cells of Cajal

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32
Q

Mechanism of Slow Wave production

A

Cyclic calcium channels open (depolarization) which brings mem potential closer to threshold
followed by K channels opening (repolarization)

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33
Q

Slow wave frequency

A

lowest in stomach (3 slow waves/min)

highest in duodenum (12 slow waves/min)

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34
Q

Swallowing coordination

A

Medulla

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35
Q

Sequence of Events in Swallowing

A

Nasopharynx closes, breathing inhibited
Glottis is closed and larynx is elevated
peristalsis in pharynx and UES relaxes

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36
Q

Primary vs Secondary Peristaltic Contraction

A

1 - high pressure behind bolus to move it down

2 - clears esophagus of remaining food

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37
Q

Receptive relaxation

A

food in upper part of GI tract will relax GI tract further down to allow passage of food, Vagovagal reflex

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38
Q

Gastroesophageal Reflux

A

tone of LES is decreased and gastric content reflux into esophagus

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39
Q

Achalasia

A

LES does not relax during swallowing and food accumulates in esophagus

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40
Q

Contractions of GI tract during fasting

A

migrating myoelectric complex, occurs at 90 minute intervals

Mediated by Motilin

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41
Q

How fats inhibit gastric emptying

A

fat stimulates CCK release which inhibits gastric emptying

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42
Q

How H+ in duodenum inhibit gastric emptying

A

direct neural reflexes

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43
Q

Segmentation contractions

A

mix intestinal contents

back-and-forth movement

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44
Q

peristaltic contractions in small intesting

A

propel the chyme
contraction behind bolus and relaxation in front
coordinated by enteric nervous system

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45
Q

Gastroileal Reflex

A

mediated by extrinsic ANS and possibly gastrin

prescence of food in the stomach triggers increased peristalsis in the ileum and relaxation of ileocecal sphincter

46
Q

Haustra

A

sac-like segments, contracts of large intestine

47
Q

Frequency of Mass movements in large intestine

A

1-3x/day

cause colonic contents to move distally

48
Q

Rectosphincteric reflex

A

rectum fills, it contracts and the internal anal sphincter relaxes

49
Q

urge to defecate

A

when rectum is filled ~25%

50
Q

Gastrocolic Reflex

A

food in stomach increases motility of the colon and increases the frequecy of mass movements
has a rapid PS component

51
Q

Hirschsprung’s Disease

A

absence of the colonic enteric nervous system resulting in constriction of involved segment

52
Q

reverse peristalsis beginning in small intesting

A

Vomiting

53
Q

Vomiting center of medulla

A

stimulated by tickling bac kof throat, gastric distention and vestibular stimulation (motion sickness)

54
Q

Chemoreceptor trigger zone

A

in 4th ventricle, activated by emetics, radiation and vestibular stimulation

55
Q

Composition of Saliva

A

High K and HCO3-
Low Na Cl
hypotonic
alpha-amylase, lingual lipase, and kallikrein

56
Q

Slow Flow rate for Saliva

A

lowest osmolarity, lowest Na, Cl and HCO3-

highest K conc

57
Q

High Flow rate for Saliva

A

highest osmolarity, closest to that of plasma

58
Q

Acinus for Saliva production

A

produces initial saliva, composition is similar to plasma

isotonic

59
Q

Ducts for Saliva production

A

modifies initial saliva, reabsorbs NaCl, secretes K and HCO3-
Aldosterone acts on these
Saliva becomes hypotoniic

60
Q

Parasympathetic Stimulation of Saliva

A

CN VII and IX
increases saliva production by causing vasodilation
Muscarinic - IP3/Ca

61
Q

Sympathetic Stimulation of Saliva

A

beta-adrenergic receptors

cAMP

62
Q

Parietal Cells

A

located in the body of stomach, secrete HCl and intrinsic factors
Stimulus is gastrin, Ach, Histamine

63
Q

Chief Cells

A

located in body of stomach, secretes pepsinogen, stimulated by vagal stimulation

64
Q

Mucous Cells

A

Antrum of Stomach, secretes mucus and pepsinogen

stimulus is ACh

65
Q

Alkaline Tide

A

pH of blood increases around the stomach due to Cl/HCO3-exchange when making acid for the stomach

66
Q

Cimetidine

A

H2 receptor blocker, inhibits H+ secretion

67
Q

ECL cells

A

inhibits histamine

68
Q

messenger for histamine

A

Gs/cAMP

69
Q

messenger for somatostatin to inhibit H+

A

Gi thus decreasing cAMP

indirect pathway to inhibit H+ secreteion is inhibiting the release of gastrin and histamine

70
Q

Protective factors for Peptic Ulcer Disease

A

mucus, HCO3, prostaglandins, mucosal blood flow, GFs

71
Q

Gastric Ulcers

A

H+ secretion is decreased
Gastrin is increased
major cause = H. pylori

72
Q

Duodenal Ulcer

A

H+ secretion is increased
gastrin in response to a meal is increased
major cause = H. pylori

73
Q

3 Drugs that block gastric H+ secretion

A

Atropine, Cimetidine, Omeprazole

74
Q

Low Flow Rates - Pancreas

A

isotonic fluid primarily of Na and Cl

75
Q

High Flow Rates - Pancreas

A

isotonic fluid, primarily Na and HCO3-

76
Q

Acinar cells - Pancreas

A

small volume, mainly Na and Cl

77
Q

Ductal cells - Pancreas

A

secreting HCO3 and absorbing Cl through HCO3/Cl-exchange

78
Q

Bile Salts

A

amphipathic

surround lipid droplets (emulsification) and aid in intestinal digestino and absorption of lipis into micells

79
Q

Micelle

A

contains FFAs and monoglycerides

80
Q

conjugates with bile acids to make bile salts

A

glycine or taurine

81
Q

where are bile acids reabsorbed

A

terminal ileum, Na-Bile acid cotransporter

82
Q

alpha-amylase

A

hydrolyze 1,4-glycosidic bonds in starch, yields maltose, ,altotriose and alpha-limit dextrans

83
Q

maltase, alpha-dextrinase and sucrase

A

part of intestinal brush border which hydrolyze oligosaccharides into glucose

84
Q

lactase

A

lactose to glucose and galactose

85
Q

trehalase

A

trehalose to glucose

86
Q

sucrase

A

sucrose into glucose and fructose

87
Q

SGLT1

A

Na-dependent cotransport with glucose in lumen of intestine

sugar transported uphill, Na transported downhill

88
Q

GLUT2

A

facilitated diffuse from inside enterocyte to blood

89
Q

Fructose

A

transported by facilitated diffusion

90
Q

Lactose intolerance

A

causes osmotic diarrhea

lack lactase in brush border

91
Q

Endopeptidases

A

hydrolyze interior peptide bonds

92
Q

Exopeptidases

A

hydrolyzes 1 AA at a time from C terminus

93
Q

Pepsin

A

optimal pH 1-3

94
Q

enterokinase

A

a brush border anzyme that makes trypsin from trypsinogen

95
Q

Trypsin

A

converts chymotrypsinogen, proelastase and procarboxypeptidase A and B to their active forms
also makes more trypsin

96
Q

Free AA

A

Na-dependent amino acid cotransport
then facilitated diffusion into blood
4 separate carrier for neutral, acidic, basic, and imino amino acids

97
Q

Dipeptides and Tripeptides

A

absorbed faster than free AA
H+-dependent cotransport of dipeptides and tripeptides on luminal memrbane
cytoplasmic peptidases make them into AA
facilitated transport into blood

98
Q

Chylomicrons

A

re-esterfied products of TGs, cholesterol ester, phospholipids with apoprotein attached so it can leave the intestinal cells

99
Q

Lymph Vessels

A

Where chylomicrons are exocytosed into and travel in until thoracic duct (then goes to blood)

100
Q

How dietary postassium is absorbed

A

small intestine by passive diffusion through the paracellular route

101
Q

Potassium in the Colon

A

K is secreted in the colon, sitmulated by aldosterone

Diarrhea = hypokalemia

102
Q

Primary ion secreted into the intestinal lumen

A

Chloride, regulated by cAMP

103
Q

Cholera toxin (from vibrio cholerae)

A

catalyzes ADP ribosylation of alpha-s of Gs coupled to AC, permanently activating it
chloride is excreted
SECRETORY DIARRHEA

104
Q

Fat Soluble Vitamins

A

A, D, E, K

incorporated into micelles

105
Q

Water Soluble Vitamins

A

absorbed by Na-dependent cotransport mechanisms

106
Q

Vit B12 absorption

A

Ileum, requires intrinsic factor

107
Q

Gastrectomy

A

loss of parietal cells, the source of intrinsic factor, lead to loss of vit B12, causes pernicious anemia

108
Q

Calcium

A

Need 1,25-dihydroxycholecalciferol from kidney to induce syn of calcium-binding protein calbindin D-28K

109
Q

Apoferritin

A

Free Fe2+ binds this to be transported into the blood

110
Q

Transferrin

A

Fe2+ bound protein in the blood taking Fe from intestine to liver or from liver to BM

111
Q

Most common cause of anemia

A

Iron deficiency

112
Q

Best channel to watch?

A

Disney channel

Human Physiology (7 decks)

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