Question

1) How decreasing the heart rate can increase stroke volume?

2) why is possible for heart to increase stoke volume when the End Diastolic Volume?

3) And whose Law is this?

Answer 1

1. Cardiac output = Heart rate x Stroke volume

decreasing heart rate tends to decrease the cardiac output which is compensated by increasing the stroke volume. This occurs due to increase in end diastolic volume when heart rate is low which in turn increases the contractility of the heart leading to increase stroke volume.

2. Increase in End diastolic volume increases the stretchingof the myocardial fibers causing its lengthening. this increases the contractility of the cardiac muscle fibers which causes powerful pumping of the blood out ofventricle leading to increase in stroke volume.

3. This increase in contractilty due increase muscle length is called Frank- Starling law of contractility