Intestinal fluid and electrolyte balance

Question 1

what is absorbed and secreted in small and large intestine

Answer 1

Small intestine - secreted HCO3-, and absorbed - K+, Na+, H20, Cl-
Large intestine - secreted HCo3-, K+ absorbed - NA, CL, H20

Question 2

How is sodium absorbed into cell?

Answer 2

NA with glucoseamino acid cotransporters
NA/H
Parallel Na-H and CL-HCO3- transporters (HC03 is removed from cell, CL- enters)
NA epithelium channels
-Goes down gradient when it enters the cell
-and then Na/K atpase pump will transport na out of cell to keep conc low

Question 3

How does chloride move into the cell

Answer 3

passivley with water - paracellular pathway

• CL-HCO3 exchaner
• Na-H, CL-CHO3 transporter

Question 4

How is CL- secreted

Answer 4

NKCC1 transporter - this gets 2 cl-, NA, K into cell on basolateral memrbane

• then CL- is being secreted out of the cell into lumen by CFTR (activated by calcium or cAMP levels)
• CL- also brings sodium with it to balance charge

Question 5

Potassium absorption and secretion

Answer 5

Absorption - paracellular pathway with water
-also with  hydrogen transporter
Secretion
- passive secretion 
-K+ with BK secretion 

-Gets into absolateral membrane via the Na+, K+ transporert and also NKCC!

Question 6

Control of absorption and secretion

Answer 6

moving more fluid from ECF into lumen, due to osmolarity

• enteric nervous system - release of Ach VIp and other secreatgogues
• paracrine system

Question 7

How does water enter cell?

Answer 7

Transcellular or paracellular pathway - always coupled to active solute movement, or by solent drag (solute dissolved and moved in)

Question 8

What causes osmotic diarrhoea

Answer 8

-pancreatic disease, large intakes of sugar and alcohols, fructose intolerance, lactose intolerance, coeliac disease

Question 9

What causes secretory diarrhoea (acute)

Answer 9

increase in active secretion
e.coli most common
Entertoxins produced by bacterial microorgansims raise intracellular cAMP leaves - anion secretion, especially CL- to maintain a charge balance in the lumen , NA is carried with it and so is water
-does not impact on nutrient coupled NA absorption
-can give ORS containing lguocse, NA for treatment

Question 10

How does ORS work?

Answer 10

ORS - has sodium, bicarbonate, glcusoe and
-only cl- is effected with the toxins, so the sodium will be absobred into cell and bring more cl- with it
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