ion channels and transporters in the heart

Question 1

the heart is primarily made of myocyte cells and these can be divided into pacemaker and non-pacemaker cells. What are the non-myocyte cells in the heart

Answer 1

endothelial cells ( line the chambers) 
fibroblasts ( create extracellular matrix)

Question 2

what do transporters do

Answer 2

allow passage of ions from one side of the cell membrane to the other but against their electrochemical gradient. Consequently energy is required in from of ATP

Question 3

funny channels are voltage gated and mediated by cAMP , what ion is released from these channels

Answer 3

sodium into the cell - opens when membrane potential is negative

Question 4

what drug inhibits a funny channel

Answer 4

ivabradine -slows HR when people are unable to take CCBs

affects phase 4

Question 5

T type calcium channels are voltage gated opening at -50mV allowing calcium into the cell at phase 0 what channels do they prompt to open

Answer 5

T for transient so shut quickly

causes L type calcium channels to open

Question 6

L type calcium channels allow calcium into the cell at phase 0 what at what voltage do they open

Answer 6

-40mV

Question 7

what drugs block L type calcium channels

Answer 7

verapamil - calcium channel blocker

Question 8

a delayed rectifier channel allows potassium OUT of the cell and is voltage gated but at what phase does this open

Answer 8

phase 3
allows repolariztion
more negative the more the gates close
blocked by class III antiarrhythmics

Question 9

the anti porter NA/CA exchanger is voltage gated and is a form of secondary transport. How many sodium and calcium are exchanged
and what does this channel maintain

Answer 9

3 NA in for 1 CA out
maintains low conc of intracellular calcium
energy comes from sodium going down electrochemical gradient

Question 10

the primary active transport NA/K atpase allows 2 K in for 3 NA out what does this maintain

Answer 10

intracellular sodium and potassium conc against their electrochemical gradients

Question 11

what inhibits NA/K ATPase pump

Answer 11

digoxin

Digoxin induces an increase in intracellular sodium that will drive an influx of calcium in the heart and cause an increase in contractility. Cardiac output increases with a subsequent decrease in ventricular filling pressures
Digoxin exhibits its therapeutic and toxic effects by poisoning the sodium-potassium ATPase. The subsequent increase in intracellular sodium leads to increased intracellular calcium by decreasing calcium expulsion through the sodium-calcium, cation exchanger.

Question 12

what cells are unable to generate their own AP

Answer 12

non-pacemaker cells

Question 13

in non pace maker cells what is the major depolarising cation

Answer 13

sodium

Question 14

in pacemaker cells what is the major depolarising cation

Answer 14

calcium

Question 15

in non pace maker cells there are fast sodium channels they are voltage gated and allows sodium into the cell at phase 0 causing rapid depolarisation of the MP and becoming briefly positive , what blocks this

Answer 15

tetrodoxin from puffer fish
flecanide which is a Class 1 anti-arrhythmic drug - which slows depolarisation and so velocity of conduction through the heart

Question 16

transient potassium channels allow potassium out of the cell in phase 1 and then in phase 2 l type calcium channels open allowing calcium into the cell at -40 which maintains what

Answer 16

the plateau phase

Question 17

delayed rectifier channels aka slow potassium channels allows potassium out of the cell cause re-polarization what Block these

Answer 17

Class 3 antiarrhythmics e.g. sotalol and amiodarone

Question 18

potassium leak channels maintain the resting potential of potassium what other channel that is voltage gated and can be blocked by magnesium also contributed to maintain the resting potential of potassium

Answer 18

inward rectifier channel

Question 19

what other channel is found in both pacemaker and non-pacemaker cells

Answer 19

NA/K ATPase channels

Question 20

in excitation contraction coupling L type calcium channels at -40mV allows claim into the cell near SR triggering release of CA via RYR - what blocks RYR

Answer 20

CCBs causing less release of claim thereby exposing fewer binding sites

Question 21

RYR are ligand receptors to calcium moving into the cytoplasm and cause a large rapid release of calcium what can they be inhibited by

Answer 21

dantrolene

Question 22

The sodium/calcium exchanger anti-porter helps maintain low intracellular claim with 1 Ca out - what form of transport is this with sodium

Answer 22

secondary transport

Question 23

CA ATPase tranporters aka SERCA pump is a primary pump refills what

Answer 23

refills the SR with calcium