Heart & Cardiac Cycle

What is the difference in the thickness of the walks of the atria and ventricles?

Ventricles have THICKER walls with MORE muscle, this produces STRONGER CONTRACTIONS

Why is the wall of the left ventricle thicker than the right ventricle?

• to produce STRONGER contractions

• to create HIGHER pressure

• so blood can be pumped around the body

How can pressure be increased?

And therefore, how can the pressure in the chamber in the heart be increased? And what does this have an effect on?

• space/size of chamber decreasing

• number of particles increasing

• The chamber contracting

• The volume of blood inside the chamber increasing

- this has an effect on the valves opening or closing

When do valves open?

When the pressure behind the valve is higher than in front

When do valves close?

When pressure behind valve is lower than in front

Describe the process of atrial diastole.

• atria relaxes

• space inside atria decreases

• so pressure inside atria decreases

• So pressure inside atria is lower than in veins

• So blood moves from vena cava into atria

• So volume of blood in atria increases

• So pressure in atria increases

• So pressure inside atria is higher than the ventricles

• So atrioventricular valves open

• Blood moved from atria to ventricles

Describe the process of ventricular diastole.

• ventricles relax

Describe the process atrial systole.

• atria contracts

• so space in atria decreases

• so pressure inside atria increases

• so more blood moves from atria to ventricles via atrioventricular valves

• so volume of blood in ventricles increases

Describe the process ventricular systole.

• ventricles contract

• so space in ventricles decreases

• so pressure inside atria is ventricles increases

• so atrioventricular valves close

The pressure inside ventricles is HIGHER than in arteries:

• so semi-lunar valve opens

• So blood moves up into pulmonary artery