3.6.1.3 Myogenic control of heart rate

Question 1

What does it mean that cardiac muscle is myogenic?

Answer 1

• even when removed from the body the heart will keep beating provided the muscle is kept alive
• can contract and relax without receiving external electrical impulses

Question 2

SAN

Answer 2

• collection of cells where the electrical impulse is generated
• sometimes referred to as pacemake

Question 3

How is heartbeat initiated and coordinated?

Answer 3

• The SAN sends waves of electrical activity / impulses across atria causing atrial contraction
• AVN delays the impulse whilst blood leaves the atria completely into ventricles
• Excitation wave cannot pass into ventricular walls due to non conducting connective tissue
• AVN then sends / conducts a wave of electrical activity / impulses down Bundle of His / Purkyne fibres
• Ventricles contract from base upwards

Question 4

What is the function of Purkyne fibres?

Answer 4

To carry / transmit wave of electrical activity / impulses causing ventricles to contract from base up