Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

Gastrointestinal > Water Balance in the GI Tract > Flashcards

Water Balance in the GI Tract Flashcards

1
Q

What does faeces normally contain?

A

100ml of water along with 50ml cellulose, bilirubin and bacteria.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

What is intestinal fluid movement always coupled to?

A

Solute movement.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

What 2 routes may water move through?

A

Transcellular or paracellular routes.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

Name the 5 principle mechanisms of sodium transport.

A
  1. Na+/glucose co-transport.
  2. Na+/amino acid co-transport.
  3. Na+/H+ exchange.
  4. Parallel Na+/H+ and Cl-/HCO3- exchange.
  5. Epithelial Na+ channels (ENaC).
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

What is the most important sodium transport in the post-prandial phase?

A

Na+/glucose co-transport and Na+/amino acid co-transport.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

Where does sodium/glucose/amino acid co-transport occur?

A

Throughout the small intestine.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

Where does Na+/H+ exchange occur?

A

In the duodenum and jejunum.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

What is Na+/H+ exchange stimulated by?

A

Luminal bicarbonate.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

What pumps sodium from the enterocyte into the interstitial fluid?

A

Na+/K+ATPase.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

Where does parallel Na+/H+ and Cl-/HCO3- exchange occur?

A

In the ileum and colon.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

When is parallel Na+/H+ and Cl-/HCO3- exchange most important?

A

In the interdigestive period.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

Where are epithelial Na+ channels and what are they regulated by?

A

The colon (particularly distal), regulated by aldosterone.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

What type of transport is Na+/glucose and Na+/amino acid co-transport?

A

Secondary active transport.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

What does it mean when it is said that Na+/glucose and Na+/amino acid co-transport and the Na+/K+ATPase are electrogenic?

A

It creates an electrical gradient.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

What does the electrical gradient produced by Na+/glucose and Na+/amino acid co-transport and the Na+/K+ATPase cause?

A

The lumen to be negative which drives the parallel absorption of Cl-.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

Is Na+/glucose and Na+/amino acid co-transport regulated?

A

No.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

What transporters are at the apical and basolateral membranes of enterocytes in Na+/H+ exchange?

A

Basolateral - NHE1. Apical - NHE2, NHE3.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

What is the function of the NHE1 transporter?

A

It regulates cytoplasmic pH (is present in most cells).

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

What stimulates Na+/H+ exchange at the apical membrane in the jejunum?

A

The alkaline environment of the lumen due to presence of bicarbonate from the pancreas.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

Is Na+/H+ exchange electroneutral?

A

Yes.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

In Na+/H+ and CI-/HCO3- exchange in parallel, what is pumped into and out of the cell?

A

In: sodium and chloride.
Out: hydrogen and bicarbonate.

22
Q

Is Na+/H+ and CI-/HCO3- exchange in parallel electroneutral?

A

Yes.

23
Q

What regulates Is Na+/H+ and CI-/HCO3- exchange in parallel and how?

A

Intracellular cAMP, cGMP and calcium - all reduce NaCl absorption.

24
Q

How does E.coli cause diarrhoea?

A

It releases a heat stable enterotoxin which activates adenylyl cyclase and increases intracellular cAMP.

25
Q

What are epithelial sodium channels mediated by?

A

Increased by aldosterone, not regulated by cAMP or cGMP.

26
Q

What are the functions aldosterone has involving ENaC?

A
  1. Opens ENaC (seconds).
  2. Inserts more ENaC into membrane from intracellular vesicle pool (minutes).
  3. Increases synthesis of ENaC and sodium potassium pump (hours).
27
Q

Is ENaC electroneutral?

A

No, electrogenic.

28
Q

What are the 2 routes that chloride can be absorbed in?

A

Transcellular or paracellular.

29
Q

In the small intestine what provides the driving force of chloride absorption?

A

Electrogenic transport of Na+ through Na+/glucose and Na+/amino acid co-transport.

30
Q

In the large intestine what provides the driving force of chloride absorption?

A

Electrogenic movement of Na+ through ENaC.

31
Q

What are the other mechanisms of absorption of chloride?

A

Cl-/HCO3- exchange (ileum, proximal and distal colon), parallel Na+/H+ and Cl-/HCO3- exchange (ileum and proximal colon).

32
Q

What usually occurs more, chloride absorption of chloride secretion?

A

Absorption.

33
Q

What type of cells is chloride secreted from?

A

Crypt cells.

34
Q

What 3 processes involved on the basolateral membrane cause an increase in intracellular chloride?

A

Na+/K+ATPase, Na+/K+/2Cl- co-transporter, K+ channels (IK1 and BK).

35
Q

What drives the Na+/K+/2Cl- transporter?

A

Low intracellular sodium (produced by Na+/K+ATPase).

36
Q

How does K+ then leave the cell?

A

Through K+ channels.

37
Q

What causes Chloride to move across the apical membrane and through which transporter?

A

Increased concentration of intracellular chloride (produced an electrochemical gradient). CFTR.

38
Q

How does sodium then get secreted into the lumen?

A

Lumen negative potential develops, so sodium is secreted through paracellular pathway.

39
Q

What causes stimulation of the CFTR channel?

A

Calcium and cAMP.

40
Q

Why is there normally little or no secretion of chloride?

A

Apical CFTR is either closer or not present.

41
Q

What causes secretion of chloride to occur?

A

Bacterial endotoxins (cholera toxin, heat stable enterotoxin, c.diff), hormones and neurotransmitters (e.g. VIP, guanylin, ACh, bradykinin, 5-HT), immune cell products (prostaglandins, histamine), some laxatives e.g. bile acids.

42
Q

How does activation of CFTR occur?

A

Indirectly as a result of generation of second messengers e.g. cAMP (cholera, VIP, histamine), cGMP (heat stable enterotoxin, guanylin), Ca2+ (ACh, bradykinin, 5-HT).

43
Q

What 2 mechanisms allow increased conductance of chloride?

A

Opening of CFTR, insertion of CFTR from intracellular vesicles into the membrane.

44
Q

What type of diarrhoea is produced from increased chloride secretion?

A

Secretory diarrhoea.

45
Q

What are the possible complications of diarrhoea?

A

Dehydration, metabolic acidosis and hypokalaemia.

46
Q

What are the 4 main mechanisms of diarrhoea?

A

Impaired absorption of NaCl, excessive secretion, non-absorbable/poorly absorbable solutes in intestinal lumen (e.g. lactase deficiency), hypermotility.

47
Q

What transport mechanism does rehydration therapy exploit?

A

SGLT1 (contains glucose so allows more absorption of sodium).

48
Q

What are the actions of opioids on the alimentary tract?

A

Inhibition of enteric neurones, decreased peristalsis, increased segmentation, increased fluid absorption, constriction of pyloric and ileocaecal and anal sphincters, increased tone of large intestine.

49
Q

What are the major opioid agonists used in diarrhoea?

A

Codeine (only really used if analgesic action needed as well), diphenoxylate and loperamide (last 2 have low CNS peneration and low solubility in water.

50
Q

What anti-diarrhoeal inhibits enkephalinase to raise endogenous enkephalin levels?

A

Racecadotril (prodrug of thiorphan), not licensed in Scotland.

Gastrointestinal (26 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions