Cardio Deck 2: ionic physiology of the heart really broken down

Question 1

Phase zero of ventricle?

Answer 1

rapid depolarization of heart, opening of voltage gated Na+ channels

Question 2

Phase 1 of ventricle?

Answer 2

Initial repolizarziation when Na+ channels close and voltage gated K+ open

Question 3

Phase 2 of ventricle?

Answer 3

Plateau. Voltage gated Ca++ open to balance K+ from phase 1 that are still open. Sarcoplasmic release of Ca++ happen with intracellular Ca++ opening and myocyte contracion

Question 4

Phase 3 of ventricle?

Answer 4

Massive depolarization b/c K+ efflux from open voltage gated slow K+ channels and Ca++ channels closing

Question 5

Phase 4 of ventricle?

Answer 5

resting potential: permeability of K+ keeps it at resting potential

Question 6

Phase 0 of pacemaker?

Answer 6

Upstroke-opening of voltage gated Ca++ (DIFFERENT THAN ventricle b/c voltage gated Na+ channels are permanently deactivated b/c less negative resting potential. that is IMPORTANT in AV node to slow conduction through to ventricles!)

Question 7

Phase 2 of pacemaker?

Answer 7

It is absent

Question 8

Phase 3 of pacemaker

Answer 8

Inactivation of Ca++ channels and more K+ hannels

Question 9

Phase 4 of pacemaker?

Answer 9

slow diastolic epolarization. Ifunny channels slowly open to depolarize it. Slow here causes faster depolarization. ACHh/adenosine decrease rate of depolarization while chatecholamines increase rate b/c increase chance Ifunny channels are open.

Question 10

What is PR interval and how long does it last?

Answer 10

Conduction delay through the AV node. Should be 200 ms

Question 11

What is QRS complex and how long should it last?

Answer 11

Less than 120 ms and it is ventricular depolarization

Question 12

What is a U wave?

Answer 12

extra wave and caused by hypokalemia or bradycardia