1.4 Know the cardiac cycle and relate structure of heart to function

-Ventricles contract

-Pressure is higher in ventricles than atria

-AV valves close to prevent backflow

-Pressure higher in ventricles than arteries

-pressure forces open SL valves

ventricular systole

-Blood flows into atria via veins (due to higher pressure in veins than atria)

-Atria contract

-Atrial pressure higher than ventricles

-AV valves open

-Blood pushed into ventricles

Atrial systole

-The ventricles need to contract and force blood into the arteries

-So the valves need to close to prevent backflow of blood into the atria on contraction

Explain why the atrioventricular valves need to close (2 marks)

-The pressure increases due to initial ventricular systole

-Pressure starts to decrease due to blood being pushed into arteries

Explain why blood pressure varies in a ventricle during the cardiac cycle (2 marks)

-Relaxation of atria and ventricles

-Reduces pressure inside heart

-AV valves open

Describe cardiac diastole (2 marks)

-It is supplied with blood through the coronary circulation

-Through coronary arteries which branch off aorta

-Blood is carried to capillaries in cardiac muscle, so the red blood cells can release oxygen

State how the cardiac muscle is supplied with oxygen (3 marks)

The cycle of events for one heartbeat

Cardiac cycle definition

An area of high pressure to an area of low pressure

Blood always flows from...

Open

AV valves in atrial systole

Closed

SL valves in atrial systole

Closed

AV valves in ventricular systole

Open

SL valves in ventricular systole

Open

AV valves in cardiac diastole

Closed

SL valves in cardiac diastole

-Relaxation of atria and ventricles reduces pressure in heart

-AV valves open

Cardiac diastole

-The cycle of events for one heartbeat

-Refers to 3 stages: atrial systole, ventricular systole and cardiac diastole

State what is meant by the term cardiac cycle (2 marks)

-The maximum blood pressure is higher in the left ventricle

-Left ventricle has thicker muscle

Describe and explain the differences in maximum blood pressure between the left ventricle and the right ventricle (2 marks)

-Left ventricle has to pump blood further, whereas the right only has to pump to lungs

-High pressure from the right ventricle would damage lungs

Discuss reasons for the difference between the maximum blood pressures in each of the ventricles (2 marks)

-Ventricles contract

-AV vales close

-semilunar valves open

-blood passes into arteries

Explain what happens during ventricular systole (3 marks)

AV valves

What is the name for the bicuspid and tricuspid valves?

Aorta

artery that pumps blood from the left ventricle to the rest of the body

vena cava

veins that bring deoxygenated blood in through the right atrium to get oxygen

pulmonary artery

carries blood from the right ventricle to the lungs

pulmonary vein

carries oxygenated blood from the lungs to the left atrium

Explain what is meant by the following - “the mammalian heart is myogenic”

-the heart is able to contract without external nervous stimulation

-the sinoatrial node generates the nerve impulse that causes the heart to contract

the sinoatrial node is referred to as the …

pacemaker

-pressure increases in the ventricles

-greater pressure in the ventricles than in the atria/arteries

-causing AV valves to close

-causing SL valves to open/forcing blood into the arteries

Explain how pressure differences in the heart ensure efficient pumping of the blood into the arteries (4)