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
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 enddiastolic 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