Prunuske: Fluid Absorption and Electrolytes Flashcards
1
Q
Anismus
A
anal sphincter dyssynergia (muscle un-coordination)
2
Q
Haustra
A
pouches of hte coon
3
Q
Ileus
A
failed forward movement of intestinal contents
4
Q
purgative
A
substance that promotes bowel loosening
5
Q
Tenesmus
A
feeling you need to pass stool even when your bowels are empty
6
Q
How much water enters the gut every day and how much is absorbed?
A
9L
8.9 L absorbed
.1 excreted
7
Q
What part of the GI tract absorbs almost 90% of the fluid present?
A
Colon
8
Q
What are properties of the epithelium that control water movement?
A
- Transcellular and paracellular routes
- Water follows electronic gradients (set up by electrogenic/neutral ion transport)
- Tight jxns (w/ claudins)
9
Q
What alters the permeability of tight jxns?
A
Cytokines
Bacteria
Hormones
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
11
Q
Where are pumps located?
A
both sides
12
Q
Na/K ATPase and H/K ATPase are…
A
PUMPS
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.
14
Q
CFTR and K channels are examples of….
A
pores/channels
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
16
Q
All transporters are located on the APICAL side except…
A
PUMPS which are on both sides
17
Q
NHE Na/H and CL/HCO3 are examples of waht types of transportesr?
A
exchangers/carriers
18
Q
How do cotransporters/carriers differ from exchangers?
A
substances move in the SAME direction (symporter)
19
Q
2 Na/glucose, bile salts, AA and PEPT 1 H/Peptide are examples of….
A
cotransporters
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)
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
22
Q
What stimulates Cl secretion through a LONG reflex?
A
ACh/VIP
23
Q
What is “stroking mucosa”?
A
release of 5 hydroxytryptamine from local enterochrommaffin cells
(short reflex)
24
Q
What are agonists that increase cAMP?
A
PG, VIP, cholera toxin
25
What do PG, VIP and cholera toxin do?
promote opening of CFTR channel>
| copious secretions in the large and sml intestines
26
What secretes guanylin?
goblet and ECL cells
27
What does guanylin bind to?
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
28
What is linaclotide?
also activates GC receptors, but is used to treat CONSTIPATION
29
What drives most of absorption?
NaCl absorption
30
What exchangers promote NaCl absorption and mediate fluid uptake as WATER follows Cl to maintain osmotic balance?
NHE Na/H exchanger
Cl/HCO3 exchanger
Electroneutral
31
What do oral rehydration salts contain that promotes water uptake?
NaCl
| glucose
32
What drives FLUID absorption?
Na/glucose
| AA, bile salts
33
Is there active transport of a coutnerion in Na/glucose absorption?
NO
SGLT-1 cotransports Glucose and Na which are transported into the blood. Anions (mostly Cl) and water passively follow.
34
What is the difference between NaCl absorption and Na/Glucose absorption?
Na/Glucose is electrogenic while the other is electroneutral
35
Where does Cl secretion occur?
crypts of lieberkuhns
36
What is the major mechanism that prompts fluid entry INTO the lumen?
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
37
Why is Cl secretion electrogenic?
Na being secreted is NOT actively transported out
38
Where is Ca actively absorbed?
duodenum
39
How is Ca actively absorbed?
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
40
What enhances expression of apical Ca channel and CALBINDIN?
vit D
41
Is Ca absorption a major determinant of fluid transport?
NOPE
42
What percent of ingested Fe is absorbed?
not much
3-6%
43
Where is Fe absorbed?
duodenum
44
What dissolves Fe and reduces it to Fe2+?
gastric secretions
45
Excess absorption of Fe leads to...
hemachromatosis
decreased number of transporters
increased ferritin
46
What is a frequent complication of partial gastrectomy?
Fe def anemia
47
Is Fe a major determinant of fluid transport?
NOPE
48
What is absorbed more in the colon, ions or nutrients?
IONS!
49
How do Na and NaCl absorption in the colon differ?
Na- electrogenic
NaCl- electroneutral
50
SCFA absorption, Cl absorption and secretion and K absorption and secretion primarily occur where...
colon
51
What facilitates the dessication of stool?
Na uptake
52
How does poop get dried out?
Distal colon>
ENAC channels allow Na to enter cell>
water follows
53
Can you still dry your poop out if you have a low Na diet?
YUP
Low Na diet> increased aldosterone> increases ENAC> reclaim more Na
54
What are secretatogues?
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
What are absorbagogues?
NEGATIVE regulators: DECREASE SECRETIONS and increase Na, Cl and water absorption
SNS activity, somatostatin, aldosterone, SCFA, bile salts, opioids
56
What are the effects of diarrhea?
sig infant mortality
dehydration
electrolyte imbalance
57
What are the two types diarrhea?
1. Secretory Diarrhea
| 2. Osmotic Diarrhea
58
What is secretory diarrhea?
excess secretion of Cl and inhibition of NaCl transport
59
What causes secretory diarrhea?
infection
inflammation
VIP stimulating tumors (cholera toxin and CFTR)
60
What causes osmotic diarrhea?
poor absorption of luminal substances>
pulls water from bloodstream by osmosis
**bile acids, organic acids, MgSO4
61
Hypermotility vs. hypomotility?
Hypermotility- diarrhea
hypomotility- constipation
62
How do you tx diarrhea?
1. Antidiarrheal drugs: Increased fluid ABSORPTION and decrease secretion
2. Aplha andrenergic agonists
3. Loperamide: slows transit, increases sphincter tone AND absorption
63
How do you tx diarrhea caused by infection?
DON'T STOP IT!!
oral rehydration
64
What does fluid flux depend on?
SA--increased SA > increased absorption
Motility- decreased transit time> increased absorption
65
How long is the small intestine and how long does it take chyme to reach the ileocecal sphincter?
5 m
2-4 hrs
66
How long is the large intestine and how long does it take chyme to reach the anus?
1 m
2.5 days
67
Mass peristalsis
rapid FORWARD population (1-3x/day)
68
segmental contractions
promote mixing w/ little forward movement
69
Sphincters are normally...
tonically contracted
70
What is segmentation?
when mixing occurs and transit slows
71
The pattern of sementation depends on the frequency of...
Basal Electrical Rhythm and amplitude
72
How does BER differ in the jejunum and ileum?
12 BER prox jejunum
8 BER distal ileum
73
How do APs affect BER?
Increase amplitude of hte BER wave
| Increase sm muscle response
74
What initiates segmental contractions?
focal increase in Ca influx
75
Propagation usually occurs over a few...
cm
76
What factors increase motility (increase APs)?
```
Ach (vagus and enteric plexus)
motilin
5HT
Subst P
PG
gastrin
CCK
insulin
```
77
What factors decrease motility (decrease APs)?
Epi
secretin
glucagon
activation of opioid receptors
78
What is the primary regulator of motility?
Enteric nervous system
79
The enteric nervous system mediates reflexes through...
enteric sensory and motor neurons (modulated by CNS)
80
5HT released from mucosal enterochromaffin cells (ECL)>
stimulates sensory neurons
81
Excitatory fibers of motorneurons release...
Ach
neurokinin A
subst P
82
Inhibitory fibers of motorneurons release...
VIP
NO
on sm muscle cells
83
MCC is active...
in the FASTED state 4 hrs after a meal
84
What does the MCC depend on?
intact enteric nervous system (interrupted when meal is ingested)
85
What does hte MCC do?
sweeps out bacteria, desquamated cells, undigested food
86
does hte MCC occur in the lrg intestine?
no
87
What happens when erythromycin binds motilin receptors?
SE of diarrhea
88
Why is the ileocecal sphincter tonically contracted?
to limit reflux of colonic contents into the ileum
89
How does distension of the ileum affect the IC sphincter? distension of hte cecum?
ileum- decreased tone, promotes ileum emptying
cecum- increased tone, decreases emptyin gof ileum
90
What initiates a peristaltic reflex?
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
What initiates an intestinointestinal reflex?
Over distension/traumatization>
relaxation of entire gut
*occurs after abdominal surgery
92
What initiates an ileal-gastric reflex?
distension of thee ileum>
decreased gastric motility
*long reflex involving vaugs nerve
93
What initiates the gastro-ileal reflex?
increased gastric activity>
increased ileal contractions>
relaxes cecum and ileoceceal sphincter
*long reflex plus hormonal component (gastrin and CCK)
94
What is the BER of the LI?
SLOW
2/min at ileocecal valve
6/min at sigmoid colon
95
Why is there less effective propulasion in the LI?
teniae coli contraction is NOT well organized
96
What are Mass movements in the LI?
peristlatic-like contractions>
| lose visble haustarations and forward propulsion (a few times a day in healthy people)
97
HOw do you induce mass movements in the LI?
laxatives
| inflammation
98
What is the colonocolonic reflex?
distension in one part of the colon>
relaxation in another part of the colon
(enteric NS, modulated by SNS)
99
What is a gastrocolic reflex?
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
What type of fibers illicit the defecation reflex?
afferents
101
What type of nerves provide extrinsic input to hte colon and inhibition of the INTERNAL anal sphincter?
Pelvic nerves
102
What type of nerves stimulates hte EXTERNAL anal sphincter?
somatic pudendal
103
What forms the internal anal sphincter?
3 bands of thickened circular muscles
104
What forms the external anal sphincter?
striated muscle
| voluntary
105
What initiates the rectosphincteric reflex?
Distension of the rectum
106
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?
rectosphincteric reflex
*the distension is accomodated> internal sphincter regains tone until the passage of more contents into the rectum
107
What are the voluntary and involuntary actions that lead to defecation?
Contraction:
1. descending colon, sigmoid colon, rectum
2. diaphragm and abdominal muscles
Relaxation:
1. both sphincters
2. pelvic floor
108
What facilitates voluntary defecation?
straining
109
What muscles inhibit defecation? How do you inhibit hte inhibitory muscles?
puborectalis
Abdm muscles contract>
lowers pelvic floor>
puborectalis relaxes
110
What usually causes incontinence?
damage to external sphincters
111
What causes IBD?
```
Chrons/ulcerative colitis>
release of inlammatory mediators>
damage epithelial barrier>
increased NO syntahse>
generate excessive NO
```
112
What are SXs of IBD?
```
diarrhea
rapid dilation of colon
pain
shock
perforation
```
113
How do you tx IBD?
colon removal
114
What is the MC intestinal problem?
IBS
1/6 in us have it
115
What causes IBS?
peripheral mechanisms that disturb motor and sensory fxn (aka...we have no fucking clue)
116
What are peripheral factors in IBS?
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
How does IBS effect the intestine?
more sensitive and contracts more frequently
abd pain, gas, bloating 3+ days/mo
May switch btwn constipation and diarrhea
