Funny Current

Question 1

where is the funny current highly expressed?

Answer 1

SAN, AVN and Purkinje fibres

Question 2

what type of channel is involved?

Answer 2

HCN channel

Question 3

what is this channel permeable to

Answer 3

Na+ and K+, but mainly Na+ influx

Question 4

what activates this channel

Answer 4

repolarisation of the membrane AND increased cellular cAMP

Question 5

how is this channel modulated?

Answer 5

sympathetic (+ve) β1/2 adrenoreceptors and parasympathetic (-ve) via muscarinic M2 receptors

Question 6

drug that can inhibit the funny current

Answer 6

ivabradine

Question 7

an increase in sympathetic stimulation causes

Answer 7

increase in the magnitude of the inward directed funny current, speeding up the depolarisation as a consequence of activation

Question 8

the larger the funny current…

Answer 8

the less time required to reach threshold for phase 0 APm hence increasing the HR

Question 9

how do β blockers effect the heart rate?

Answer 9

slow it down by decreasing sympathetic effect

Question 10

effect of DIGOXIN on the funny current

Answer 10

increases parasympathetic effect, slowing down the heart rate