Pressure changes (Heart)

Contraction

Relax

Series of events that take place in one heart beat and is a continuous process

Atrium contracts, Pressure increases in atrium and volume decreases. Ventricle relax, Pressure decreases in ventricle. Atrioventricular valve is forced open due to pressure difference and semi-lunar valve is closed so blood moves from the atrium to the ventricle down the pressure gradient

Ventricle contracts, pressure increases in ventricle and volume decreases, atria relaxes, Pressure in atria is low so atrioventricular valve is forced closed (Prevents backflow of blood) and semi-lunar valve is forced open. Pressure in ventricle is greater than pressure in aorta and pulmonary artery so blood moves out ventricle into arteries away from heart. (During this atria are relaxing so are filling with blood again)

Ventricle and atria both relax, Pressure in ventricle drops below aorta and pulmonary artery so semi-lunar valve is closed. Blood returns to heart through vena cava and pulmonary vein. Pressure in atria rises above ventricle eventually so the AV is forced open repeating the process again from atrial systole.

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Open when the pressure behind the valve is higher and close when the pressure in front of the valve is higher. Prevent backflow of blood

arteries branch into narrower blood vessels called arterioles which transport blood into capillaries. The smooth muscle lining the arterioles also contract which leads to the constriction of the arteriole lumen

Can cut off blood supply to certain organs. e.g in exercise can partially cut off blood supply to stomach and intestines so respiring muscles get more blood and oxygen for respiration for ATP production