cardiac cycle

Question 1

The heart contains a number of heart valves which prevent the backflow of blood

Answer 1

This ensures the one-way circulation of blood around the body

Question 2

There are two sets of valves located within the heart:

Answer 2

• Atrioventricular valves (tricuspid and bicuspid) prevent blood in the ventricles from flowing back into the atria
• Semilunar valves (pulmonary and aortic) prevent blood in the arteries from flowing back into the ventricles

Question 3

Heart sounds are made when these two sets of valves close in response to pressure changes within the heart

Answer 3

• The first heart sound is caused by the closure of the atrioventricular valves at the start of ventricular systole
• The second heart sound is caused by the closure of the semilunar valves at the start of ventricular diastole

Question 4

cardiac cycle

Answer 4

• The cardiac cycle describes the series of events that take place in the heart over the duration of a single heartbeat. The heart beasts at an approximate rate of 60-100 times per minute, so each cardiac cycle is about 0.8 seconds long.
• It is comprised of a period of contraction (systole) and relaxation (diastole)

Question 5

systole (5) - remember, we’re pumping blood

Answer 5

Blood returning to the heart will flow into the atria and ventricles as the pressure in them is lower (due to low volume of blood)
When ventricles are ~70% full, atria will contract (atrial systole), increasing pressure in the atria and forcing blood into ventricles
As ventricles contract, ventricular pressure exceeds atrial pressure and AV valves close to prevent backflow (first heart sound)
With both sets of heart valves closed, pressure rapidly builds in the contracting ventricles (isovolumetric contraction)
When ventricular pressure exceeds blood pressure in the aorta, the aortic valve opens and blood is released into the aorta

Question 6

diastole (3)

Answer 6

As blood exits the ventricle and travels down the aorta, ventricular pressure falls
When ventricular pressure drops below aortic pressure, the aortic valve closes to prevent backflow (second heart sound)
When the ventricular pressure drops below the atrial pressure, the AV valve opens and blood can flow from atria to ventricle
Throughout the cycle, aortic pressure remains quite high as muscle and elastic fibres in the artery wall maintain blood pressure

Question 7

see slide 7 & 8

Question 8

Murmur

Answer 8

• Murmur is an abnormal sound produced by the heart valves.
• In these cases, the valves are not closing properly and there is a backflow of blood. This results in inefficient circulation.
• A person may be born with faulty valves or they may be damaged by disease
• Only 20% of heart murmurs are a medical problem.