How would each of the activities listed below affect stroke

How would each of the activities listed below affect stroke volume? [indicate whether it is increased, decreased, or would have no effect]. Give rationale for each answer

increased sympathetic stimulation of the heart;

increased parasympathetic stimulation of the heart;

decreased end diastolic volume;

blocking calcium entry into the cardiac muscle cell;

increased ventricular end diastolic volume.

Solution

Activities

Effect on stroke volume

Rationale

increased sympathetic stimulation of the heart;

Increase

Increased sympathetic stimulation (due to fright, anger, etc.) increases the heart rate. It also increases stroke volume by increasing contractility, which results in more complete ejection of blood from the heart (lower ESV).

increased parasympathetic stimulation of the heart;

Decrease

Parasympathetic activity increases after a crisis has passed. This reduces heart rate and stroke volume from their high levels, bringing cardiac output back to normal.

decreased end diastolic volume;

Decrease

Mathematical relation is SV= EDV – ESV

Thus, if EDV is low, SV will be also low

blocking calcium entry into the cardiac muscle cell;

Decrease

Absence of calcium also decreases stroke volume by lowering contractility.

increased ventricular end diastolic volume.

Increase

An increase in ventricular end diastolic volume will increase EDV and therefore stroke volume.