L02,03 - cardiac control_rev01

Question 1

action potential change of pacemaker cells/ nodal cells

Answer 1

1. slow depolarization to reach threshold:
   ➢ Na+ influx (automatically induced)
   ➢ transient Ca2+ influx
2. rapid depolarization (after threshold)
   ➢ long lasting Ca2+ influx via L-type Ca2+ channel
3. repolarization
   ➢ K+ efflux

Question 2

action potential of cardiac muscle cells

Answer 2

(1) pacemaker AP increases membrane potential to threshold
(2) rapid depolarization: Na+ influx
(3) short repolarization
* K+ efflux
(4) plateau phase (prolonged
depolarization)
* long lasting Ca2+ influx
* slow K+ efflux
(5) rapid repolarization
* K+ efflux

Question 3

calcium induced calcium release

Answer 3

Ca2+ influx via L-type Ca2+ channel induces Ca2+ release out of sarcoplasmic reticulum by opening Ryanodine receptor

Question 4

why long lasting ca2+ influx in plateau phase

Answer 4

sufficient time for Ca2+ release and contraction