Cardiac output: Human heart
Cardiac output is a measure of the amount of blood that the heart pumps per unit of time, usually measured in liters per minute. The human heart typically pumps about 5 liters of blood per minute at rest, but this can increase during physical activity or other times of increased demand.
Cardiac output is determined by two factors: heart rate and stroke volume. Heart rate is the number of times the heart beats per minute, while stroke volume is the amount of blood that the heart pumps with each beat. The formula for calculating cardiac output is:
Cardiac Output = Heart Rate x Stroke Volume
For example, if a person has a heart rate of 70 beats per minute and a stroke volume of 70 milliliters per beat, their cardiac output would be:
Cardiac Output = 70 beats/minute x 70 mL/beat = 4.9 L/minute
The heart can increase its cardiac output in response to increased demand, such as during exercise or in response to stress. This is achieved by increasing both heart rate and stroke volume. During exercise, the sympathetic nervous system is activated, leading to an increase in heart rate and the release of hormones that increase stroke volume by increasing the force of heart contractions. This allows the heart to pump more blood to meet the body’s increased demand for oxygen and nutrients.
In summary, cardiac output is the amount of blood that the heart pumps per unit of time, and it is determined by heart rate and stroke volume. The human heart typically pumps about 5 liters of blood per minute at rest, but this can increase during physical activity or other times of increased demand.
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