Physiology: cardiac action potentials

Question 1

describe what happens during phase 4 of pacemaker action potential

Answer 1

Na + K influx
transient Ca influx
decreased K efflux

Question 2

when does phase 4 of pacemaker action potential occur

Answer 2

when threshold reached

Question 3

through what channel is the Na + K influx in phase 4 of pacemaker action potential

Answer 3

HCN channel(funny current)

Question 4

what phase occurs in pacemaker action potential when threshold is reached

Answer 4

phase 0 - depolarisation

Question 5

what occurs in phase 0 of pacemaker action potential

Answer 5

Ca influx

Question 6

what occurs after phase 0 of pacemaker action potential

Answer 6

phase 3 - repolarisation

Question 7

what occurs in phase 3 of pacemaker action potential

Answer 7

K efflux

Question 8

what is phase 4 of myocyte action potential

Answer 8

phase 4 = resting phase

Question 9

what occurs in phase 4 myocyte action potential to allow threshold to be reached

Answer 9

slow leakage of Ca into cell through gap junctions between adjacent myocytes

Question 10

describe what occurs in phase 0 of myocyte action potential

Answer 10

phase 0 = depolarisation

Na influx via voltage-gated channels

Question 11

describe what occurs in phase 1 of myocyte action potential

Answer 11

phase 1 = initial repolarisation

K efflux

Question 12

describe what occurs in phase 2 of myocyte action potential

Answer 12

phase 2 = plateau phase
Ca influx, K efflux
contraction occurs(actin-myosin)

Question 13

describe what occurs in phase 3 of myocyte action potentials

Answer 13

phase 3 = repolarisation

K efflux

Question 14

what is the refractory period

Answer 14

the period where no new action potentials can occur