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GI- Week 4 > Prunuske: Fluid Absorption and Electrolytes > Flashcards

Prunuske: Fluid Absorption and Electrolytes Flashcards

1
Q

Anismus

A

anal sphincter dyssynergia (muscle un-coordination)

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2
Q

Haustra

A

pouches of hte coon

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3
Q

Ileus

A

failed forward movement of intestinal contents

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4
Q

purgative

A

substance that promotes bowel loosening

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5
Q

Tenesmus

A

feeling you need to pass stool even when your bowels are empty

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6
Q

How much water enters the gut every day and how much is absorbed?

A

9L

8.9 L absorbed

.1 excreted

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7
Q

What part of the GI tract absorbs almost 90% of the fluid present?

A

Colon

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8
Q

What are properties of the epithelium that control water movement?

A
  1. Transcellular and paracellular routes
  2. Water follows electronic gradients (set up by electrogenic/neutral ion transport)
  3. Tight jxns (w/ claudins)
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9
Q

What alters the permeability of tight jxns?

A

Cytokines

Bacteria

Hormones

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10
Q

What do pumps do?

A

PUMPing something out is ACTIVE TRANSPORT

  • uphill against electrochem gradient
  • effective at low conc
  • saturable kinetics
  • requires cell energy
  • high ionic specificity
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11
Q

Where are pumps located?

A

both sides

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12
Q

Na/K ATPase and H/K ATPase are…

A

PUMPS

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13
Q

What type of movement do channels (pores) exhibit?

A

PASSIVE (I’ll PASS through this PORE if I want to)

sorry that was stupid. i’m tired.

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14
Q

CFTR and K channels are examples of….

A

pores/channels

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15
Q

Exchangers/Carriers exhibit what type of movement? What does this mean?

A

Secondary active transport–I can move SECOND cause you moved FIRST.

Move ion/substance AGAINST the electrochemical gradient by coupling it to mvmt of another ion moving WITH the electrochemical gradient.

Antiporter

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16
Q

All transporters are located on the APICAL side except…

A

PUMPS which are on both sides

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17
Q

NHE Na/H and CL/HCO3 are examples of waht types of transportesr?

A

exchangers/carriers

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18
Q

How do cotransporters/carriers differ from exchangers?

A

substances move in the SAME direction (symporter)

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19
Q

2 Na/glucose, bile salts, AA and PEPT 1 H/Peptide are examples of….

A

cotransporters

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20
Q

In the small intestine, absorption and secretion often occur spontaneously and RIGHT next to each other. Where is this?

A

Absorption- tips of villi

Secretion- crypts (Cl ion secretion)

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21
Q

Why is there increased blood flow during a meal?

A

Blood brings O2 and GLUCOSE which help with active transport of solutes (esp Na) which requires both O2 and glucose

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22
Q

What stimulates Cl secretion through a LONG reflex?

A

ACh/VIP

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23
Q

What is “stroking mucosa”?

A

release of 5 hydroxytryptamine from local enterochrommaffin cells

(short reflex)

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24
Q

What are agonists that increase cAMP?

A

PG, VIP, cholera toxin

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25
Q

What do PG, VIP and cholera toxin do?

A

promote opening of CFTR channel>

copious secretions in the large and sml intestines

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26
Q

What secretes guanylin?

A

goblet and ECL cells

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27
Q

What does guanylin bind to?

A

GC-C receptor on epithelial cells>
increased conc of intracellular cGMP>
INCREASED Cl secretion through the CFTR into the lumen

*heat stable toxin produced by E. coli induces secretion the same way

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28
Q

What is linaclotide?

A

also activates GC receptors, but is used to treat CONSTIPATION

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29
Q

What drives most of absorption?

A

NaCl absorption

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30
Q

What exchangers promote NaCl absorption and mediate fluid uptake as WATER follows Cl to maintain osmotic balance?

A

NHE Na/H exchanger
Cl/HCO3 exchanger

Electroneutral

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31
Q

What do oral rehydration salts contain that promotes water uptake?

A

NaCl

glucose

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32
Q

What drives FLUID absorption?

A

Na/glucose

AA, bile salts

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33
Q

Is there active transport of a coutnerion in Na/glucose absorption?

A

NO

SGLT-1 cotransports Glucose and Na which are transported into the blood. Anions (mostly Cl) and water passively follow.

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34
Q

What is the difference between NaCl absorption and Na/Glucose absorption?

A

Na/Glucose is electrogenic while the other is electroneutral

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35
Q

Where does Cl secretion occur?

A

crypts of lieberkuhns

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36
Q

What is the major mechanism that prompts fluid entry INTO the lumen?

A

Cl is actively taken up by NKCC1 at the basolateral membrane>
Cl leaves luminal side via CFTR
K leaves basilar side via Ca activated K channel

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37
Q

Why is Cl secretion electrogenic?

A

Na being secreted is NOT actively transported out

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38
Q

Where is Ca actively absorbed?

A

duodenum

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39
Q

How is Ca actively absorbed?

A

Electrochemical gradient drives Ca inward through Ca channel on apical membrane>
intracellular Ca binds CALBINDIN>
Then….

  1. Basolateral Ca ATPase pumps Ca out
  2. Ca exchanged w/ Na
  3. Ca is exocytosed
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40
Q

What enhances expression of apical Ca channel and CALBINDIN?

A

vit D

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41
Q

Is Ca absorption a major determinant of fluid transport?

A

NOPE

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42
Q

What percent of ingested Fe is absorbed?

A

not much

3-6%

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43
Q

Where is Fe absorbed?

A

duodenum

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44
Q

What dissolves Fe and reduces it to Fe2+?

A

gastric secretions

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45
Q

Excess absorption of Fe leads to…

A

hemachromatosis
decreased number of transporters
increased ferritin

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46
Q

What is a frequent complication of partial gastrectomy?

A

Fe def anemia

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47
Q

Is Fe a major determinant of fluid transport?

A

NOPE

48
Q

What is absorbed more in the colon, ions or nutrients?

A

IONS!

49
Q

How do Na and NaCl absorption in the colon differ?

A

Na- electrogenic

NaCl- electroneutral

50
Q

SCFA absorption, Cl absorption and secretion and K absorption and secretion primarily occur where…

A

colon

51
Q

What facilitates the dessication of stool?

A

Na uptake

52
Q

How does poop get dried out?

A

Distal colon>
ENAC channels allow Na to enter cell>
water follows

53
Q

Can you still dry your poop out if you have a low Na diet?

A

YUP

Low Na diet> increased aldosterone> increases ENAC> reclaim more Na

54
Q

What are secretatogues?

A

positive regulators: INCREASE SECRETIONS and decrease Na, Cl and water absorption

PNS activity (Ach), VIP/NO, histamine, PG, gastrin , secretin, motilin, 5HT, LCFA and bacterial toxins

55
Q

What are absorbagogues?

A

NEGATIVE regulators: DECREASE SECRETIONS and increase Na, Cl and water absorption

SNS activity, somatostatin, aldosterone, SCFA, bile salts, opioids

56
Q

What are the effects of diarrhea?

A

sig infant mortality
dehydration
electrolyte imbalance

57
Q

What are the two types diarrhea?

A
  1. Secretory Diarrhea

2. Osmotic Diarrhea

58
Q

What is secretory diarrhea?

A

excess secretion of Cl and inhibition of NaCl transport

59
Q

What causes secretory diarrhea?

A

infection
inflammation
VIP stimulating tumors (cholera toxin and CFTR)

60
Q

What causes osmotic diarrhea?

A

poor absorption of luminal substances>
pulls water from bloodstream by osmosis

**bile acids, organic acids, MgSO4

61
Q

Hypermotility vs. hypomotility?

A

Hypermotility- diarrhea

hypomotility- constipation

62
Q

How do you tx diarrhea?

A
  1. Antidiarrheal drugs: Increased fluid ABSORPTION and decrease secretion
  2. Aplha andrenergic agonists
  3. Loperamide: slows transit, increases sphincter tone AND absorption
63
Q

How do you tx diarrhea caused by infection?

A

DON’T STOP IT!!

oral rehydration

64
Q

What does fluid flux depend on?

A

SA–increased SA > increased absorption

Motility- decreased transit time> increased absorption

65
Q

How long is the small intestine and how long does it take chyme to reach the ileocecal sphincter?

A

5 m

2-4 hrs

66
Q

How long is the large intestine and how long does it take chyme to reach the anus?

A

1 m

2.5 days

67
Q

Mass peristalsis

A

rapid FORWARD population (1-3x/day)

68
Q

segmental contractions

A

promote mixing w/ little forward movement

69
Q

Sphincters are normally…

A

tonically contracted

70
Q

What is segmentation?

A

when mixing occurs and transit slows

71
Q

The pattern of sementation depends on the frequency of…

A

Basal Electrical Rhythm and amplitude

72
Q

How does BER differ in the jejunum and ileum?

A

12 BER prox jejunum

8 BER distal ileum

73
Q

How do APs affect BER?

A

Increase amplitude of hte BER wave

Increase sm muscle response

74
Q

What initiates segmental contractions?

A

focal increase in Ca influx

75
Q

Propagation usually occurs over a few…

A

cm

76
Q

What factors increase motility (increase APs)?

A 
Ach (vagus and enteric plexus)
motilin
5HT
Subst P
PG
gastrin
CCK 
insulin
77
Q

What factors decrease motility (decrease APs)?

A

Epi
secretin
glucagon
activation of opioid receptors

78
Q

What is the primary regulator of motility?

A

Enteric nervous system

79
Q

The enteric nervous system mediates reflexes through…

A

enteric sensory and motor neurons (modulated by CNS)

80
Q

5HT released from mucosal enterochromaffin cells (ECL)>

A

stimulates sensory neurons

81
Q

Excitatory fibers of motorneurons release…

A

Ach
neurokinin A
subst P

82
Q

Inhibitory fibers of motorneurons release…

A

VIP
NO

on sm muscle cells

83
Q

MCC is active…

A

in the FASTED state 4 hrs after a meal

84
Q

What does the MCC depend on?

A

intact enteric nervous system (interrupted when meal is ingested)

85
Q

What does hte MCC do?

A

sweeps out bacteria, desquamated cells, undigested food

86
Q

does hte MCC occur in the lrg intestine?

A

no

87
Q

What happens when erythromycin binds motilin receptors?

A

SE of diarrhea

88
Q

Why is the ileocecal sphincter tonically contracted?

A

to limit reflux of colonic contents into the ileum

89
Q

How does distension of the ileum affect the IC sphincter? distension of hte cecum?

A

ileum- decreased tone, promotes ileum emptying

cecum- increased tone, decreases emptyin gof ileum

90
Q

What initiates a peristaltic reflex?

A

Distension of gut wall (peristalsis)>
proximal contraction and distal relaxation

Can be decreased or increased by ANS but depend on an intact enteric nervous system

91
Q

What initiates an intestinointestinal reflex?

A

Over distension/traumatization>
relaxation of entire gut

*occurs after abdominal surgery

92
Q

What initiates an ileal-gastric reflex?

A

distension of thee ileum>
decreased gastric motility

*long reflex involving vaugs nerve

93
Q

What initiates the gastro-ileal reflex?

A

increased gastric activity>
increased ileal contractions>
relaxes cecum and ileoceceal sphincter

*long reflex plus hormonal component (gastrin and CCK)

94
Q

What is the BER of the LI?

A

SLOW

2/min at ileocecal valve
6/min at sigmoid colon

95
Q

Why is there less effective propulasion in the LI?

A

teniae coli contraction is NOT well organized

96
Q

What are Mass movements in the LI?

A

peristlatic-like contractions>

lose visble haustarations and forward propulsion (a few times a day in healthy people)

97
Q

HOw do you induce mass movements in the LI?

A

laxatives

inflammation

98
Q

What is the colonocolonic reflex?

A

distension in one part of the colon>
relaxation in another part of the colon

(enteric NS, modulated by SNS)

99
Q

What is a gastrocolic reflex?

A

Gastric distension>
increased colon motility and urge to defecate

i.e. you eat bfast in the morning and it makes you have to poop

(5HT and Ach)

100
Q

What type of fibers illicit the defecation reflex?

A

afferents

101
Q

What type of nerves provide extrinsic input to hte colon and inhibition of the INTERNAL anal sphincter?

A

Pelvic nerves

102
Q

What type of nerves stimulates hte EXTERNAL anal sphincter?

A

somatic pudendal

103
Q

What forms the internal anal sphincter?

A

3 bands of thickened circular muscles

104
Q

What forms the external anal sphincter?

A

striated muscle

voluntary

105
Q

What initiates the rectosphincteric reflex?

A

Distension of the rectum

106
Q

What leads to the urge to defecate, relaxation of the internal sphincter and reflex contraction of the external anal sphincter to prevent almost pooping you pants?

A

rectosphincteric reflex

*the distension is accomodated> internal sphincter regains tone until the passage of more contents into the rectum

107
Q

What are the voluntary and involuntary actions that lead to defecation?

A

Contraction:

  1. descending colon, sigmoid colon, rectum
  2. diaphragm and abdominal muscles

Relaxation:

  1. both sphincters
  2. pelvic floor
108
Q

What facilitates voluntary defecation?

A

straining

109
Q

What muscles inhibit defecation? How do you inhibit hte inhibitory muscles?

A

puborectalis

Abdm muscles contract>
lowers pelvic floor>
puborectalis relaxes

110
Q

What usually causes incontinence?

A

damage to external sphincters

111
Q

What causes IBD?

A 
Chrons/ulcerative colitis>
release of inlammatory mediators>
damage epithelial barrier>
increased NO syntahse>
generate excessive NO
112
Q

What are SXs of IBD?

A 
diarrhea
rapid dilation of colon
pain
shock
perforation
113
Q

How do you tx IBD?

A

colon removal

114
Q

What is the MC intestinal problem?

A

IBS

1/6 in us have it

115
Q

What causes IBS?

A

peripheral mechanisms that disturb motor and sensory fxn (aka…we have no fucking clue)

116
Q

What are peripheral factors in IBS?

A
  1. colonic motility is delayed> constipation
  2. colnic motility is accelearated> diarrhea (vagal induction)
  3. increased sensitivity to food (bile acid and SFA> 5HT)
  4. increased small bowel and mucosal permeability
117
Q

How does IBS effect the intestine?

A

more sensitive and contracts more frequently

abd pain, gas, bloating 3+ days/mo

May switch btwn constipation and diarrhea

GI- Week 4 (12 decks)

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