Heart - biology

What happens during atrial systole?

• blood returns to heart due to skeletal and muscles involved in breathing

• blood flows into the 2 atrium under low pressure from the pulmonary vein and vena cava

• as atria fills, increasing pressure of blood against atrioventricular valves push them open

• blood then leaks into the ventricles

What happens in ventricular systole?

• slight delay after atrial systole

• ventricles contract from the base and goes upwards, increasing pressure in the ventricles

• pressure forces open semilunar valves and pushes blood out through pulmonary arteries and aorta

• pressure of blood against atrioventricular valves closes them so there isn’t backflow back into the atria

what happens in cardiac diastole?

• atria and ventricle relax

• elastic recoil lowers pressure in atria and ventricles

• closes the semilunar valves so there is no backflow to the ventricles

• coronary arteries fill

• low pressure in atria helps draw blood into heart from veins

What are the features of an open circulatory system?

• blood circulates in large open spaces

• single heart pumps blood out into cavities surrounding the organs

• when heart muscle relaxes blood is drawn from cavity back into the heart through small valved openings

What are features of a closed circulatory system?

• blood is enclosed in tubes (vessels)

• generates higher pressure as blood is forced along fairly narrow channels

• blood travels faster so blood system is more efficient at delivering substances around body

What feature determines if the animal has a single circulatory system?

blood flows through the heart once for each complete circuit of the body

What feature determines if the animal has a double circulatory system?

blood flows through heart twice for each complete circuit

1. right ventricle pumps deoxygenated blood to lungs where it receives oxygen

2. oxygenated blood returns to the heart to be pumped a second time by left ventricle to the rest of the body

What is mass flow?

a process where a liquid and all the particles it contains are transported in one direction due to a difference in pressure

Where are the atrioventricular valves located?

between the atria and ventricles

Where are the semilunar valves located?

aortic valve - between left ventricle and aorta

pulmonary valve - between right ventricle and pulmonary artery

What are the features of an artery?

• narrow lumen

• thicker walls

• more collagen, smooth muscle and elastic fibres

• no valves

What are the features of a vein?

• wide lumen

• thinner walls

• less collagen and smooth muscle, fewer elastic fibres

• has valves

How does blood move through arteries?

• when heart contracts (systole), blood is forced into arteries and their elastic walls stretch to accommodate the blood

• during diastole, elasticity of artery walls cause them to recoil behind the blood, which helps push the blood forward and smoothes blood flow

• as each section stretches and recoils, blood flow pulses in the arteries

Why do arteries have thick walls?

So the walls can withstand the high pressure generated as the blood is forced against the walls

How does blood move through capillaries?

• blood moves in a steady flow

• flows slowly due to narrow lumens creating friction against the capillary wall

• slower steady flow allows exchange between blood and surrounding cells

How does blood move through veins?

• blood flows steadily and without pulses

• under relatively low pressure

• blood flow is assisted by contraction of skeletal muscles during limb movements and breathing

• lower pressure in chest cavity when breathing helps draw blood back into heart

What are the 3 phases of a cardiac cycle in order?

atrial systole → ventricular systole → diastole

Which wall is the thickest and why?

Left ventricle, pumps blood through the systemic circuit (around the body)