A Level Biology: The Cardiac Cycle

Name the three main stages of the cardiac cycle in order

atrial systole, ventricle systole, diastole

Describe atrial systole

the atria contract, creating a small increase in pressure Atrial pressure is higher than ventricular pressure, pushing blood into the ventricles through the AV valve. vol of ventricles increase to maximum.

Describe ventricular systole

the ventricles contract at the base of the heart. when ventricular pressure exceeds atrial pressure the semi lunar valve opens pumping blood upwards towards the arteries. therefore volume in ventricles decreases to minimum

Describe diastole

the muscular walls of all four chambers relax and elastic recoil allows the chambers to increase in volume so blood can flow in through the veins

What is the key function of valves in the heart?

the ensure blood flows in the right direction

Where are the atria-ventricular valves located?

between the atrium and ventricle

Describe the opening of atria-ventricular valves

when the ventricular walls relax, the pressure in the ventricles drop below the pressure in the atria- the blood in the atria pushes the atria-ventricular valves open

Describe the closing of the atria-ventricular valves

after the atria-ventricular valve opens, blood enters the atria and ventricles, causing pressure to slowly rise. When the ventricle is full, a swirling action around the valve causes it to close

Where are the semilunar valves located?

between the atria and the arteries

Name the two arteries of the heart

aorta and pulmonary artery

Name the two veins of the heart

vena cava and pulmonary vein

Describe the closing of the semilunar valves

before ventricular systole, the pressure in the arteries is higher than the pressure in the ventricles, causing the semilunar valves to be closed

Describe the opening of the semilunar valves

when ventricular systole takes place, the pressure in the ventricle exceeds the pressure in the arteries, causing the semilunar valves to be pushed open

Suggest why a faulty atrioventricular valve could lead to symptoms of breathlessness and lack of energy.

valves don’t shut properly

some backflow of blood from ventricles to atria

during ventricular systole

lower blood pressure

less efficient supply of oxygen

blood pressure in lungs increases

During the cardiac cycle, the changes in pressure that occur in the left atrium and in the left ventricle are different. Explain these differences.

pressure changes are smaller in the atrium than ventricle

the atrium has less cardiac muscle than ventricle

the atrium does not have to push the blood as far as the ventricle has to

the increase in pressure begins in the atrium before the ventricle

atrial systole has to happen before ventricular systole in order for the ventricle to fill with blood

increase in atrial pressure causes increase in pressure in ventricle