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PSIO EXAM 3 > GI 3 > Flashcards

GI 3 Flashcards

1
Q

Nerve supply to the GI tract is

A

extrinsic (sympathetic, parasympathetic) and intrinsic (enteric nervous system)

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2
Q

Extrinsic

A

Can modulate the enteric NS

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3
Q

Intrinsic

A

Contained in myenteric and submucosal plexuses, back and forth communication
Afferents to the plexuses come from chemo- & mechanoreceptors

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4
Q

enteric nervous system is the

A

digestive brain

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5
Q

3 layers of smooth muscle

A

Outer longitudinal muscle
Inner circular muscle
Muscularis mucosa

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6
Q

layers of GI tract

A

lumen, epithelium, lamina propia, musculares mucosae, submucosa, submucosal plexus, myenteric plexus, serosa, blood

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7
Q

submucosal plexus

A

contains GI nervous system,
epithelium, lamina propia, and submucosa

also called Meissner’s secretion

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8
Q

myenteric plexus

A

contains GI nervous system
circular muscles and longitudinal muscle

also called Auerbach’s plexus

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9
Q

Smooth muscle cells are connected by ___ _______ that form an _______ _________

A

Smooth muscle cells are connected by gap junctions that form an electrical syncytium

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10
Q

circular muscles

A

Affects radial dimensions;

Contraction decreases diameter

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11
Q

longitudinal muscle

A

Affects anterior-posterior dimensions;

Contraction decreases length

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12
Q

Insmooth muscle, there is no _______

A

troponin, rather, the interaction of actin and myosin is controlled by the binding of Ca2+to another protein,calmodulin

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13
Q

protein used from muscle contraction in smooth muscle

A

calmodulin

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14
Q

tonic contractile activity

A 
fairly stable contractions
Upper Esophageal Sphincter
Lower Esophageal Sphincter
Ileocecal sphincter
Internal anal sphincter
Orad stomach
Pylorus
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15
Q

phasic contractile activity

A 
periodic contractions
Pylorus
Esophagus
Antrum
Small intestine
Colon
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16
Q

which part of the GI tract has both types of contracts activity

A

pylorus

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17
Q

Segmentation Contractions

A

contractions in both directions to mix contents
Mix chyme and expose to pancreatic enzymes / secretions
Produce no forward movement
Found in the intestine

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18
Q

Peristaltic Contractions

A

proximal muscle contracts, distal muscle relaxes
Propel chyme towards large intestine

Involves several neurotransmitters including Ach and substance P (orad) as well as VIP and nitric oxide (caudad)

Found in esophagus, stomach, intestine

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19
Q

contraction

A

Circular muscle contracts, longitudinal muscle relaxes; segment narrows and lengthens

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20
Q

relaxation

A

Circular muscle relaxes, longitudinal muscle contracts, segment widens and shortens

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21
Q

feces

A

unabsorbed small intestinal content in the large intestine

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22
Q

Segmentation Contractions

A

via the haustrations
Occur in the cecum and proximal colon
Serve to mix contents
Associated with haustra

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23
Q

Peristalsis in the large intestine

A

propels

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24
Q

Mass Movements in the large intestine

A

move contents over longer distances, happen 1-3 times a day final movement is to the rectum to await defecation
Large infrequent peristaltic contractions, 1-3 times a day

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25
Q

cyclical pattern is associated with which contractile activity

A

phasic

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26
Q

myogenic contractility is important because

A

the guy has some contractility without any nervous input whatsoever

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27
Q

Luminal contents will cause

A

basal contractility without any nervous influence at all

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28
Q

there is a constantinhibitory toneof

A

VIPandNOon the gut, to prevent / slow down this contractility

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29
Q

Any treatment or condition that removes or inactivates inhibitory motor neurons results in

A

tonic contracture and continuous uncoordinated activity of the circular muscles

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30
Q

example of hyper irritable states cause by inactivation or removal of inhibitory motor neurons

A

Achalsia, Hirschprung’s disease, fecal incontinence

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31
Q

MCC phase 1

A

takes 45 to 60 minutes
0 slow waves with spike
myoelectic activity but no contraction amplitude

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32
Q

MMC phase 2

A

take 30 to 45 minutes
50 % are slow waves with spike
Intermittent, peristaltic, contractions, variable amplitude

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33
Q

MMC phase 3

A

5 to 10 minutes 10 slow waves with spike
Action potentials rapidly propagated along GI axis
Strong peristaltic contractions

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34
Q

Interdigestive PeriodMigrating Motility Complex is Initiated during

A

fasting
Begins in the stomach
Moves undigested material to colon
Repeats every 90-120 min during fasting

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35
Q

major complex starches

A

amylopectin and amylose

major digestion being in the mouth and they are reduced to disaccharides

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36
Q

disaccharides

A

sucrose, maltose, lactose, trehalose, digestion being in the intestine

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37
Q

Digestion and absorption of Carbohydrates

A

salivary alpha amylase enzyme is active in the mouth and remains active in stomach until acid inactivates it, salivary and pancreatic amylase in the duodenum produce alpha dextrins, maltose and maltostiose
then enzymes on brush border hydrolyze starch products to glucose

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38
Q

Enzymes on intestinal brush border

A

hydrolyze disaccharides to make simple sugars

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39
Q

Absorption: Apical Carbs

A

Na+-glucose cotransport
Na+-galactose cotransport
Fructose facilitated diffusion

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40
Q

Absorption: Basolateral Carbs

A

All by facilitated diffusion with GLUT 2 transporter, glucose, galactose and fructose

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41
Q

The function of insulin is to keep the

A

level of glucose in the blood stream in within a normal range

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42
Q

Glucose enters the bloodstream, which stimulates

A

the pancreas to release insulin in just the right amount
Insulin allows glucose to enter cells throughout the body, where it is used as fuel.
Excess glucose is stored in the liver

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43
Q

Incretins are hormones that help

A

the process of insulin getting glucose into cells

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44
Q

Incretin hormones

A

Glucagon-like peptide-1 (GLP-1)

Glucose-dependent insulinotropic peptide (GIP).

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45
Q

function of (GLP-1) and (GIP)

A

enhance glucose dependent insulin secretion
suppress postprandial glucagon secretion
slow gastric emptying
reduce food intake and body weight
promote beta cell health

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46
Q

GLP-1 is produced

A

postprandially by intestinal cells

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47
Q

GLP-1 in the pancreas

A

stimulates insulin biosynthesis and secretion
Inhibits glucagon secretion
inhibit beta cell apoptosis

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48
Q

GLP-1 ini the heart and brain

A

has protective effects
increase cardiac output
decreases appetite

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49
Q

GLP-1 in the periphery

A

Insulin sensitivity is increased by improved insulin signaling, insulin sensitivity and reduced gluconeogenesis

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50
Q

GLP-1 in the stomach

A

reduces gastric emptying

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51
Q

Digestion and absorption of Proteins- pepsin

A

begins in the stomach with the activation of gastrointestinal proteases
in a low pH pepsinogen secreted from chief cells becomes pepsin

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52
Q

Bulk digestion and Absorption of Proteins

A

occurs in intestine by the action of the pancreatic enzymes

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53
Q

Active forms of protein digestive enzymes also produced in the intestine

A

enterokinase in the brush border convert trypsinogen into trypsin
Trypsinogen activates pancreatic proezymes to their active form

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54
Q

protein final products of digestion to be absorbed

A

amino acids, dipeptides, tripeptides

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55
Q

Absorption: Apical Proteins

A

Na+-amino acid cotransport

H+-di/tripeptide cotransport

56
Q

Absorption: Basolateral Proteins

A

after the H+-di/tripeptide cotransport there is further breakdown to amino acids then
facilitated diffusion OR
Reabsorbed unchanged

57
Q

Digestion and absorption of lipids digestive enzymes

A

important for fat digestion include lingual lipase, gastric and pancreatic lipases, cholesterol ester hydrolase and phospholipase A2

58
Q

the final digestive product of lipids

A

monoglycerides, cholesterol, lysolecithin and free fatty acids

59
Q

Absorption of lipids via

A

micelles and chylomicrons in the jejunum

60
Q

Triglyceride final products

A

monoglycerides and fatty acids

61
Q

cholesterol esters final products

A

cholesterol and fatty acids

62
Q

Phospholipid final products

A

lysolecithin and free fatty acids

63
Q

Lipids are delivered to

A

liver fat cardiac and skeletal tissue

locally broken down by lipase

64
Q

what are vitamins

A

organic compound that cannot be made by the body so we must get from the diet

65
Q

fat soluble vitamins

A

A, D, E , K

66
Q

Absorption of Water Soluble Vitamins occurs in

A

the jejunum

67
Q

which vitamins cross apical membrane by the Na+ cotransport

A

thiamine, riboflavin, vitamin c , biotin, folic acid, niacin, pantothenic acid

68
Q

which water soluble vitamin crossed by simple diffusion

A

B6 pyridoxine

69
Q

Digestion and Absorption of Fat Soluble Vitamins

A

Released from food in the small intestine
Processed in the same manner as dietary lipids
Taken up into micelles
Delivered to luminal membrane
Absorbed by simple diffusion
Inside the cell, incorporated into chylomicrons
Extruded by exocytosis into the lymph

70
Q

Fat Soluble Vitamins are passively

A

absorbed

71
Q

Water absorption by the GI tract
is ______ and in response
to ________

A

passive and in response to somatic forces

72
Q

water absorbed in duodenum and jejunum

A

4000 ml

73
Q

water absorbed in ileum

A

3500 ml

74
Q

water absorbed in colon

A

1400 ml

75
Q

water lost in feces

A

100 mk

76
Q

amount of Na+ entering the GI tracts

A

about 25-35 grams a day from diet and Gi secretions

77
Q

the GI tract is _____ at conserving NA+

A

very efficient

78
Q

we have ____ _____ mechanisms operating to absorb NA+ through the intestine and colon

A

Several different

79
Q

intestinal sodium absorption is always

A

isometric

80
Q

Major site for Na+ absorption

A

the jejunum

Absorbs more than ½ of total Na+

81
Q

sodium countertransport in jejunum

A

Na+-H+

82
Q

sodium coupled absorption in jejunum

A

Na+-coupled sugar/amino acid absorption

83
Q

Net absorption in jejunum

A

NaHCO3

84
Q

Net absorption in ileum

A

NaCl

85
Q

Ileum

A

HCO3 secretion

86
Q

where does fecal fluid become alkaline

A

the ileum

87
Q

Intestinal Potassium Absorption

A

Passive diffusion through tight junctions and lateral intercellular spaces of enterocytes in both the jejunum and ileum

As water is absorbed, luminal K+ increases, resulting in K+ absorption

88
Q

Driving force of Intestinal Potassium Absorption

A

is K+ concentration difference between lumen and blood.

89
Q

Colonic Absorption net result

A

fecal fluid tends to be alkaline and has a relatively high K + concentration

90
Q

Aldosterone-sensitive luminal Na+ channel

A

increase Na+ absorption

91
Q

colonic villus cells

A

K+ can be absorbed or secreted by colonic villus cells,

flow rate dependent, more K+ is lost in diarrhea

92
Q

Aldosterone increases _____ and _____ of ____ channels

A

number and sensitivity of Na+ channels

93
Q

K+ secretion is

A

flow dependent

94
Q

overall function of intestines

A

absorption predominates by villus epithelial cells

there is also secretion by crypt epithelial cells

95
Q

Main electrolyte secreted

A

chloride

96
Q

how much isotonic alkaline fluid is secreted from crypts of Lieberkϋhn in a day

A

2 to 3 litters

97
Q

function of isotonic alkaline fluid

A

main fluidity of chyme and dilute noxious (Poison) substances

98
Q

what makes up isotonic alkaline fluid

A

water and electrolytes

99
Q

Two channel types in Electrogenic Cl- Secretion from Crypts

A

Na/K/Cl tritransproter on basolateral membrane

Cl- channel (CFTR) on luminal membrane

100
Q

Mechanism of Electrogenic Cl- Secretion from Crypts

A

Na/K pump keeps sodium concentration low; drives Cl- in via Na/K/Cl tritransporter;
Increases CL- concentration which favors efflux on luminal side.
Adds lumen negativity which drives Na+ secretion paracellularly

101
Q

Normally (unstimulated state), crypts secrete very little

A

Cl- because apical channels are closed or not present

102
Q

Cl- secretion requires activation by

A

calcium or cAMP

103
Q

What activates cAMP or Ca2+?

A

Hormones or neurotransmitters
Bacterial endotoxins
Immune cell products
laxatives

104
Q

examples of Bacterial endotoxins that activates Cl- secretion

A

e coli, and cholera (cAMP)

105
Q

Hormones or neurotransmitters that activates Cl- secretion

A 
Ach =  cAMP
VIP = Ca2+
106
Q

Immune cell products that activates Cl- secretion

A

histmine cAMP

107
Q

Resulting activation of cAMP or Ca2+ activates

A

activates preexisting Cl- channels or inserts them into the apical membrane.
End result is increased Cl- secretion

108
Q

laxatives and Cl- secretion

A

activation of Ca2+

109
Q

Causes of Diarrhea Secretory Diarrhea

A

cholera

110
Q

Diarrhea

A

a condition in which feces are discharged from the bowels frequently and in a liquid form

111
Q

Infectious/Inflammatory Diarrhea

A

Salmonella, rotovirus

associated with widespread destruction of absorptive epithelium

112
Q

most diarrhea cases are caused by

A

enteric infections

113
Q

many types of diarrhea are

A

mixed

114
Q

osmotic diarrhea

A

an example is lactose intolerant

Buildup of lactose in GI lumen holds water with it causes diarrhea

115
Q

Deranged Motility causing Diarrhea

A

an example is hypermotility in some cases of IBS
If food moves too quickly through the GI tract, there is not enough time for sufficient nutrients and water to be absorbed resulting in diarrhea

116
Q

Constipation

A

a condition in which there is difficulty in emptying the bowels, usually associated with hardened feces

117
Q

causes of constipation

A

Slow movement of the contents in the large intestine, colon
Fecal evacuation disorder
Combination (slow movement; inability to evacuate)

118
Q

risk factors for constipation

A

less exercise, sedentary lifestyle, diseases or disabilities that create immobility

use of medications

119
Q

The longer stool remains in the colon

A

the more water continues to be absorbed, creating hard stools

120
Q

Potential for total body water and electrolyte loss is

A

enormous when you have diarrhea and cannot properly absorb water

121
Q

Jejunum Na+

A

Actively absorbed; absorption enhanced by sugars, amino acids

122
Q

Jejunum K+

A

Passively absorbed when concentration rises because of water absorption

123
Q

Jejunum Cl- and HCO3

A

absorbed

124
Q

ileum Na+

A

Actively absorbed

125
Q

Colon Na+

A

Actively absorbed

126
Q

ileum K+

A

Passively absorbed when concentration rises because of water absorption

127
Q

Colon K+

A

net secretion

128
Q

ileum/ colon Cl-

A

Absorbed, some in exchange for HCO3-

129
Q

ileum/ colon HCO3-

A

Secreted, partly in exchange for Cl-

130
Q

Dietary cobalamin (B12) released from food by

A

pepsin

131
Q

B12 is delivered to

A

liver and red bone marrow

132
Q

a consequence of a gastrectomy is

A

the loss of intrinsic factor

133
Q

Intestinal Water Transport if 9 L is ingested each day how?

A

2 L of water and 5 g of sodium are ingested each day (Diet)

7 L of salivary, gastric, pancreatic, biliary and intestinal secretions

134
Q

how much water is absorbed

A

8.8 L of water and 30 g of sodium are absorbed each day

135
Q

where is water absorbed

A

7 to 8 L absorbed in small intestine

1 to 2 L absorbed in colon

136
Q

how much water is excreted

A

0.1 to 0.2 L excreted in feces

PSIO EXAM 3 (8 decks)

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