Physiology of fluid balance - Week 5

Question 1

Absorption of Water in the GI Tract is Largely Driven by…

Answer 1

Reabsorption of Na+

Question 2

What are the principle mechanisms of water absorption in the GI tract?

Answer 2

Na+/glucose co-transport
Na+/amino acid co-transport
Na+/H+ exchange
Parallel Na+/H+ and Cl-/HCO3- exchange
Epithelial Na+ channels (ENaC)

Question 3

What are the major mechanisms of postprandial Na+ absorption in the jejunum?

Answer 3

Na+/glucose and Na+/amino acid cotransport

Question 4

Na+/H+ and CI-/HCO3- exchange in parallel primarily occurs in…

Answer 4

Ileum and proximal colon

Question 5

Na+/H+ and CI-/HCO3- exchange in parallel is regulated by…

Answer 5

cAMP

Question 6

What is the role of Epithelial Na+ channels (ENaC)?

Answer 6

mediate electrogenic Na+ absorption in the distal colon

Question 7

Epithelial Na+ channels (ENaC) are regulated by…

Answer 7

Aldosterone

Question 8

What provides the driving force for Cl- absorption?

Answer 8

Negative luminal potential

Question 9

What is the role of CFTR in fluid absorption?

Answer 9

CFTR is indirectly activated by various toxins. CFTR then mediates Cl- clearance, resulting in secretory diarrhoea.

Question 10

Give 4 general causes of diarrhoea.

Answer 10

Impaired absorption of NaCl, Non-absorbable, or poorly absorbable, solutes in intestinal lumen, Hypermotility, Excessive secretion

Question 11

How do rehydration therapies work?

Answer 11

Exploit SGLT1 channel - Na+ drives absorption of water

Question 12

Which class of drugs are known to have anti-diarrhoeal activity?

Answer 12

Opioids

Question 13

The major opioid agonists used in diarrhoea are…

Answer 13

codeine, diphenoxylate, loperamide