The cardiac cycle Ventricular filling the diastole refers to the period of the cardiac cycle during which the ventricles are filling with blood the systole refers to the period of the cardiac cycle during which the ventricles are actively contracting and pumping blood out of the heart

The cardiac cycle Ventricular filling end-diastolic volume refers to the volume of blood in the ventricle at the end of ventricular filling Atrial contraction

The cardiac cycle

Ventricular contraction isovolumetric ventricular contraction ventricular ejection Ventricular relaxation isovolumetric relaxation

The cardiac cycle

Cardiac output Cardiac output (CO) is the volume of blood pumped by each ventricle per minute Cardiac output depends on the heart rate and the stroke volume CO = HR x SV

Stoke volume Stroke volume is the difference between the volume of the ventricle just before contraction (end-diastolic volume) and the volume of the ventricle at the end of a contraction (end-systolic volume).

Four factors affecting the end- diastolic volume 1. Venous filling pressure 2. Pressures generated during atrial contraction 3. Distensibility of the ventricular wall 4. The time available for filling the ventricla

Regulation of Cardiac output Regulation of heart rate regulation of the stroke volume