Chapter+20

Page 211 - Data based question: Heart action and blood pressures 1. blood is pumped from atria to ventricles 0 seconds to 0.1 seconds (N.B the slight rise in atrial pressure at 0.15seconds is probably due to the AV valve bulging back into the atria as ventricular systole starts) 2. Ventricles start to contract at 0.1 seconds 3. AV valve closes at 0.1 seconds (atrial pressure falls below ventricular pressure) 4. SL valve opens at 0.15 seconds (ventricular pressure rises above arterial pressure) 5. SL valve closes at 0.4 seconds (ventricular pressure falls below arterial pressure) 6. Blood is pumped from the ventricle to the artery from 0.15 to 0.4 seconds. 7. a) Blood in the ventricle is at a maximum at 0.1 seconds (just before the SL valve opens) b) Blood in the ventricle is at a minimum at 0.35 seconds (at the peak of ventricular systole)

Note - this diagram is not especially clear. I'd prefer to use a clearer diagram to explain this first.