Major Strategies of Ion and Osmoregulation in SW Flashcards
1
Q
What are the 3 major strategies of ion and osmoregulation in SW fish?
A
- retain solutes
- do not drink
- special salt secreting gland
2
Q
Why do fish retain solutes?
A
- expensive to make urea (3ATP)
- counteracts toxicity of urea @ high conc.
3
Q
What is ureosmoregulation? (4)
A
- urea as osmolyte
- [urea] 100X greater than in mammals
- inward directed osmotic gradient
- TMAO retained to counterbalance
4
Q
What is TMAO?
A
- osmolyte that protects proteins from being denatured by urea conc.
5
Q
What are the 2 main solute retention sites?
A
- gill
- kidney
6
Q
Why is the gill a good retention site?
A
- low urea permeability (1/50 - 1/100 less)
- active urea transport
7
Q
-Why is the kidney a good retention site?
A
- active urea transporters
- urea cotransporters
8
Q
Active NaCl excretion is done by what organ
A
- rectal gland
9
Q
What is a rectal gland?
A
- digiform organ
10
Q
What is the rate of rectal gland secretions of Na and Cl (2)
A
- approximates SW
- 2X that of plasma
11
Q
What is NaCl secretion stimulated by? What does it do?
A
- arterial natriuretic peptide
- stimulates secretion in kidney from within rectal gland
12
Q
Where is Na/K ATPase found
A
- on secretory tubule
