The Cardiac Cycle

Question 1

What happens during atrial systole?

Answer 1

Atrium walls contract, increasing the blood pressure in the atria, pushing the blood through the bicuspid and tricuspid valves down into the ventricles.

Question 2

What happens during ventricular systole?

Answer 2

Ventricle walls contract increasing the pressure in the ventricles. Forces blood up through the semi-lunar valves out of the heart, into the pulmonary artery and aorta.

Question 3

What happens during diastole?

Answer 3

The ventricles relax so increase in volume, decreasing the pressure. This risks the blood in the pulmonary artery and aorta flowing backwards so the semi-Luna valves shut at their bases. The atria also relax, causing the pressure the decrease and them to fill with blood, restarting the cycle.

Question 4

Name the three sets of valves in the heart

Answer 4

Semi lunar valves
The bicuspid valve
The tricuspid valve

Question 5

Why do atria have thinner walls of muscle than ventricles?

Answer 5

Because the atria only have to pump blood to the ventricles whereas ventricles have to pump blood further (the lungs and rest of the body)

Question 6

What is the role of the sino-atrial node (SAN)?

Answer 6

It acts as a pacemaker by causing a wave of electrical stimulation across the atria to cause them to contract together

Question 7

What is the role of the atria-ventricular node (AVN)?

Answer 7

Delays the electrical stimulus from the SAN then causes the electrical stimulation to spread to the ventricles but only once the atria have finished contracting