Cardiac Action Potential

Question 1

What is autorhythm?

Answer 1

Heart contracts rhythmically due to APs it generates itself.

Question 2

What are the two types of cardiac cell?

Answer 2

Contractile cells (99% do not initiate APs)
Autorhythmic cells (do not contract/ initiate APs)

Question 3

What is myocardium?

Answer 3

Muscular tissue of the heart.

Question 4

What are the four specific sites that non-contractile cells demonstrate autorhythm?

Answer 4

• Sinoatrial node (SA node)
• Atrioventricular node (AV node)
• bundle of His (AV node)
• Purkinje fibres

Question 5

Which of these is the pacemaker of heart?

Answer 5

Sinoatrial node.

Question 6

What is the function of the AV node?

Answer 6

• Only conducting pathway between atrial muscle and bundle of His.
• Allows delay of excitation to allow time for blood to get to ventricles from atria
• Can take over as pacemaker if impulses from SA node fail to reach AV node.

Question 7

What are the 5 phases of voltage change across cardiac myocytes?

Answer 7

1) Depolarisation
2) Early repolarisation
3) Plateau phase
4) Late repolarisation
5) Resting potential