Mammalian Heart Function Overview

Question 1

Myogenic

Answer 1

Heart’s ability to self-contract

Question 2

Sinoatrial Node (SAN)

Answer 2

Specialized fibers in the right atrium, heart’s pacemaker

tissue is responsible for initiating the heartbeat

Question 3

Atrioventricular Node (AVN)

Answer 3

Located between atria, passes electrical signals from the atria to the ventricles, resulting in ventricular systole

Question 4

Bundle of His

Answer 4

Conducts excitation from atrioventricular node to apex

Question 5

Purkyne Fibres

Answer 5

Branches of bundle of His, carry excitation upwards

Question 6

Atrial Systole

Answer 6

Left and right atria contract together; blood is squeezed from the atria through the atrioventricular valves into the ventricles, down a pressure gradient.

Question 7

Ventricular Systole

Answer 7

Ventricular blood pressure rises very quickly to a level above the arteries; semilunar valves open and blood rushes out of ventricles into the arteries

Question 8

Cardiac Diastole

Answer 8

Once ventricular contraction is complete, heart muscle starts to relax, heart starts to fill with blood again and semilunar valves close

Question 9

Semilunar Valves

Answer 9

Close in aorta and pulmonary arteries to prevent backflow

Question 10

Why is the left ventricular wall so much thicker than the right ventricular walls?

Answer 10

Blood is pumped through the aorta and needs sufficient pressure to overcome the resistance of the systemic circulation

Question 11

Why are there so many mitochondria in cardiac muscle?

Answer 11

Supply energy for contraction

Question 12

Why is there a delay before the AVN depolarises the ventricular walls?

Answer 12

To allow the atria to finish contracting