Cardiac Cycle Control of Heat beat

Question 1

What is a cardiac cycle?

Answer 1

The sequence of events that makes up one heartbeat.

Question 2

When does the cardiac cycle begin?

Answer 2

When the sinoatrial node initiates the heartbeat

Question 3

Why do the valves between the atria and ventricles open?

Answer 3

Because atrial pressure remains slightly greater than ventricular pressure until the ventricles are fully distended

Question 4

Why are the pulmonary and aortic outflow valves closed?

Answer 4

As pulmonary artery and aortic pressures are greater than ventricular pressure

Question 5

What happens during atrial systole?

Answer 5

Atrial contraction forces a small amount of additional blood into the ventricles

Question 6

What happens during isovolumic ventricular contraction and relaxation?

Answer 6

The first phase of ventricular contraction pushes atrioventricular valves closed but does not create enough pressure to open the semilunar valves. As ventricles relax, pressure in the ventricles falls, blood flows back into the cusps of the semilunar valves and snaps them closed

Question 7

What happens during ventricular ejection?

Answer 7

As ventricular pressure rises and exceeds pressure in the arteries, the semilunar valves open and blood is ejected