lec 6. regulation of Na+ and Ca+

Question 1

Sodium is regulated by…

Answer 1

Na+/K+ ATPase

Question 2

its important to regulate Na+ because…

Answer 2

it sets up a driving force needed by many transporters and can dictate the function of a cell

Question 3

examples of importance of Na+ regulation

Answer 3

1) NKCC2 in apical membrane of thick ascending limb requires low intracellular Na+ to work. If Na+ increases it can lead to diuresis
2) if intracellular Na+ increases in excitable cells it can lower conduction of action potentials
3) allows for directional transport (rather than just recycling) of Na+ coming through amiloride sensitive channels on apical side of collecting ducts

Question 4

its important to regulate Ca+ because

Answer 4

its an important second messenger in many signalling pathways

Question 5

examples of importance of Ca+ regulation

Answer 5

1) in pancreatic acinar cells, digestive enzymes stimulate Ca+ release which aids the fusion of vesicles to the membrane to release the enzymes

Question 6

Calcium is regulated by…

Answer 6

Na+/Ca+ Exchanger and Ca+ ATPase - to keep intracellular Ca+ low!

Question 7

Na+/Ca+ Exchanger

Answer 7

moves 3 Na+ in, and 1 Ca+ out

main function: keep intracellular Ca+ low!

electrogenic

member of SLC8 family, and CaCA superfamily

in mammals, the three forms are called NXC1-3

Question 8

Ca+ ATPase

Answer 8

part of P-type ATPase (same as Na+/K+)

transfers Ca+ after a muscle has contracted

3 types - PMCA, SERCA, SPCA

Question 9

PMCA

Answer 9

move Ca+ out of cell through plasma membrane

Question 10

SERCA

Answer 10

move Ca+ into Ca+ stores (SR and ER)

Question 11

SPCA

Answer 11

pump found on golgi apparatus

Question 12

VOCC

Answer 12

• plasma membrane pathway of calcium signalling

voltage gated Ca+ channel found on excitable cells and activated by depolarisation to increase intracellular Ca+

Question 13

ROCC

Answer 13

• plasma membrane pathway of calcium signalling

receptor operated, found on excitable cells and nerve terminals, increases intracellular Ca+
EX. NMDA

Question 14

Mechanically Activated Ca+ channels

Answer 14

• plasma membrane pathway of calcium signalling

respond to cell deformation, found on many cells, increases intracellular Ca+
EX. stretch activated channels

Question 15

SOCC

Answer 15

• plasma membrane pathway of calcium signalling

store operated, activated after depletion of Ca+ stores, increases intracellular Ca+

Question 16

IP3

Answer 16

• store membrane pathway of calcium signalling

activated by IP3 binding, and is expressed in most cells, increases intracellular Ca+

Question 17

Ryanodine Receptors

Answer 17

• store membrane pathway of calcium signalling

activated by low concentration of ryanodine, and also caffeine and cADP ribose, and is found in excitable cells, increases intracellular Ca+

Question 18

Orai Channel

Answer 18

SOCC activated by by STIM1 when Ca+ is depleted in the ER due to IP3 signalling