Cardiac Cycle

Question 1

What happens in diastole?

Answer 1

• Blood returns to the
atria of the heart
through the pulmonary
vein (lungs) and vena
cava (body).
• The filling of blood in
the atria increase the
pressure and forces
the AV valves open.
• Pressure is higher in
the aorta and the
pulmonary artery than
in the ventricles so SL
valves close

Question 2

What happens in atrial systole?

Answer 2

• Atria (atrial walls)
contract
• Pushing the remaining
blood into the
ventricles
• Ventricles remain
relaxed and recoil

Question 3

What happens in ventricular systole?

Answer 3

• The atria relax and after a short
delay the ventricles fill with blood.
• The walls of the ventricles
contract and the pressure
increases forcing the AV valves to
shut. Preventing backflow.
• The pressure increases in the
ventricles and becomes higher than
in the aorta and pulmonary artery –
so SL valves open
• Blood is pushed away from the
heart through pulmonary arteries
and aorta

Question 4

How do you calculate cardiac output?

Answer 4

CO= stroke volume x heart rate

Question 5

General principles of the cardiac cycle?

Answer 5

• Contraction of the myocardium generates pressure changes which
result in the orderly movement of blood.
• Blood flows from an area of high pressure to an area of low pressure,
unless flow is blocked by a valve.
• Events on the right and left sides of the heart are the same, but
pressures are lower on the right.