1. Pressure changes during the cardiac cycle

2. P N L Atrial systole Ventricle systole Diastole

3. What is happening at L-M L: Ventricular systole starts Ventricular pressure greater than atrial pressure. Therefore AV valves shut. M: Ventricular systole Pressure in ventricle exceeds that in aorta Semilunar valves open Blood enters aorta.

4. What is happening and N and P N: Start of ventricular diastole Ventricular pressure less than aortic pressure Semilunar valves shut Preventing backflow of blood into ventricles P: Ventricular diastole Pressure in ventricle drops below atrium AV valves open Blood enters ventricle

5. Why is the max pressure in the left atrium lower than max pressure in the left ventricle? Ventricle has thicker muscle wall Generates a higher pressure as it contracts Pumps blood a greater distance then atria