Na+ and Ca2+ regulation

Question 1

concentration of Na ICF and ECF

Answer 1

ICF = 15 mM
ECF = 145mM

Question 2

What inhibits NKCC2 in TAL

Answer 2

high Na+ conc in cell

Question 3

nernst Na value?

Answer 3

+60 mV

Question 4

Na+/K+ pump role and steps

Answer 4

remove Na+ from cell, exhanchge for K+

The 3 Na+ bind and cause phosphorylation, conformational change so NA+ dissociate

K+ into the cleft, causes dephosphorylation, so K+ enters the cell

Question 5

3 ways the Na+/K+ pump can become saturated

Answer 5

ATP, Na+, K+ if too much of any

Question 6

what can inhibit the Na+/K+ pump

Answer 6

cardiac glycosides - ouabain and digoxin

Question 7

Ca2+ EC and IC concentraions

Answer 7

ICF = 100nm ECF = 1mM 10,000 fold increase in the extracellular fluid

Question 8

nernst value for calcium

Answer 8

+120

Question 9

Na/Ca exchanger role and structure

Answer 9

3Na+ into cell, 1 Ca2+ out of the cell
10 transmembrane domains
hydrophobic cleft in centre where ions bind
3rd Na+ enters and equilibrium changes s ca2+ leaves

Question 10

the 3 Ca2+ pumps in the cell

Answer 10

PMCA- plasma membrane calcium pump to the out of cell
SERCA- calcium pump of sacra or smooth ER as Ca store activated by IP3
SPCA- on golgi, also transports Mn+

Question 11

the 3 type of calcium gated channel

Answer 11

voltage gated - VOCC if depolarised (excitatory cells )
receptor operated - ROCC in secretory cells and nerve terminals
Mechanically operated - street as cell vol increase

Question 12

Ryanodine receptors ? role what activates

Answer 12

channels on the ER that if IC calcium low they release from their stores SOCC

also activated by caffeine and CADP-ribose

Question 13

ORAI channel - role and what activates it

Answer 13

role is to restore Ca2+ store in the ER
calcium is bound to STIM1 in the ER, when it is released there is a conformatonal change in STIM1 and it activates the ORAI channels to mop up calcium

Question 14

why is it important to regulate intracellular Na+

Answer 14

In epithelial cells - Creates the tranepithelial osmotic gradient responsible for counter-current multiplication

in kidney - Activity of NKCC depends upon inward Na gradient

In excitable cells - It will take longer for the potential to develop

Problems with the propogation of the action potential

Slower conduction of the action potential

Question 15

genes for the Ca/Na exchanger

Answer 15

Members of the SLC8 gene family. Part of a much larger CaCA superfamily.
In mammals three forms exist named NCX1-3