Lecture 8 things to work on

Question 1

What are the electrical properties of secretory epithelia?

Answer 1

• leaky for water secretion

- tight (eg. K+ secretion in the cortical collecting duct)

Question 2

What is the ion transport on secretory epithelia?

Answer 2

• active secretion of Cl- ions
• Na+ and water follow
• there is secretion of an isosmotic NaCl solution

Question 3

Describe the apical membrane properties (water secretion) of secretory epithelia

Answer 3

• there is high permeability to Cl- due to the presence of Cl- channels
• Cl- channels need to be activated to be open

Question 4

What are two examples of Cl- channels in secretory epithelia?

Answer 4

• cAMP activated Cl- channels eg. CFTR

- Ca2+ activated Cl- channels eg. TMEM16A

Question 5

What is the hydraulic conductivity of secretory epithelia like?

Answer 5

it is very high and there is secretion of an isosmotic NaCl solution

Question 6

What is the hormonal/nervous control of secretory epithelia like?

Answer 6

• It is under precise control

- there are low basal rates of secretion which are increased by hormonal and nervous inputs

Question 7

What is the problem with cystic fibrosis?

Answer 7

There is a mutation in the CFTR Cl- channel which means that Cl- is not secreted which means that there is decreased H2O secretion which contributes to thick mucous in various organs