initiation of the cardiac AP

Question 1

ohm’s law

Answer 1

Iab= delta Vab/Rab

what determines the current

Question 2

determinants AP propagation

Answer 2

difference in voltage between cells

resistance between cells - function of the connexin

threshold for AP firing - in neighbouring cell
- need to pump more charge into the neighbouring cell if the threshold is really

Question 3

Sino-atrial node

Answer 3

AP spreads from SA node to left atrium

where cardiac AP begins

cells depolarize spontaneously and fire APs at regular intrinsic rate

can be modulated by PNS and SNS (pacemaker activity)

goes to AV node - impulse does not spread directly because of the atrioventricular ring

Question 4

pacemaker channel

Answer 4

what we care about in SA node

structure like a potassium channel

a non-selective cation channel

gated by cAMP

also called the HCN channel - hyperpolarisation-activated, cyclic nucleotide gated channel

aka funny current (gated by both potassium and sodium)