Learn: Cardiac Cycle, Cardiac Output and Blood Pressure

Welcome!Great to see you again! You've already learned about the heart and blood vessels, so now we’ll build on that to understand how the heart works during the cardiac cycle, what affects cardiac output, and how these relate to blood pressure.

What is the Cardiac Cycle?The cardiac cycle refers to the sequence of events that occur during one heartbeat. It includes periods of contraction (systole) and relaxation (diastole) in the heart chambers. This cycle ensures that blood is pumped efficiently to the lungs and body.

Phases of the Cardiac CycleThere are three main phases: atrial systole (atria contract), ventricular systole (ventricles contract), and diastole (heart relaxes and fills with blood). The valves in the heart prevent backflow during these phases.

Cardiac OutputCardiac output is the amount of blood pumped by the heart per minute. It is calculated using the formula: Cardiac Output = Stroke Volume × Heart Rate. Stroke volume is the amount of blood ejected with each beat, and heart rate is the number of beats per minute.

Blood PressureBlood pressure is the force exerted by blood on the walls of blood vessels. It is measured in mmHg and recorded as two numbers: systolic pressure (pressure during ventricular contraction) and diastolic pressure (pressure during relaxation).

Factors Affecting Blood PressureBlood pressure is influenced by cardiac output, blood vessel diameter, and blood volume. For example, narrowing of blood vessels increases resistance, leading to higher pressure.

Review Time!Great work! You've learned about the cardiac cycle, cardiac output, and blood pressure. Now let’s test your understanding.