What are heart rate and stroke volume and how are they affected by exercise?
Stroke volume is the volume of blood ejected by each beat of the heart, or more precisely, the difference between the volume of the ventricle before contraction (end-diastolic volume) and the volume of the ventricle at the end of a contraction (end-systolic volume). A change in the end diastolic or systolic volume can cause differences in stroke volume and also cardiac output, which is the volume of blood pumped per unit time for a ventricle. For example an increase in venous filling pressure will cause an increase in the end diastolic volume, and an increase in stroke volume. However, during some circumstances, the heart rate might increase while the stroke volume remains the same. This is due to the fact that pacemaker cells are stimulated causing an increase in heart rate. The rate of production of ATP and other factors in the ventricular cell increases as well, so as to quicken the pace of ventricular work. This makes the rate of ventricular emptying increase during systole in orde
