Cardiac output is equal to the:
(a) Difference between the end-diastolic volume and the end-systolic volume
(b) Product of heart rate and stroke volume
(c) Difference between the stroke volume at rest and the stroke volume during exercise
(d) Stroke volume less the end-systolic volume
(e) Product of heart rate and blood pressure

Verified step by step guidance

1. Step 1: Understand the definition of cardiac output. Cardiac output is the volume of blood the heart pumps per minute.
2. Step 2: Recall the two main factors that determine cardiac output: heart rate (HR), which is the number of heartbeats per minute, and stroke volume (SV), which is the amount of blood pumped out of the ventricle with each beat.
3. Step 3: Use the formula for cardiac output, which is the product of heart rate and stroke volume: \(\text{Cardiac Output} = \text{Heart Rate} \times \text{Stroke Volume}\).
4. Step 4: Evaluate each option in the problem based on this formula. For example, option (b) matches the formula directly.
5. Step 5: Conclude that the correct expression for cardiac output is the product of heart rate and stroke volume, as given in option (b).

Key Concepts

Cardiac Output

Cardiac output is the total volume of blood the heart pumps per minute. It is a key measure of heart function and is calculated by multiplying the heart rate (beats per minute) by the stroke volume (amount of blood pumped per beat). This reflects the efficiency of the cardiovascular system in delivering oxygenated blood.

Stroke Volume

Stroke volume is the amount of blood ejected by the left ventricle during each heartbeat. It is determined by the difference between the end-diastolic volume (blood in the ventricle before contraction) and the end-systolic volume (blood remaining after contraction). Stroke volume influences cardiac output directly.

Heart Rate

Heart rate is the number of heartbeats per minute. It varies with physical activity, stress, and health status. Along with stroke volume, heart rate determines cardiac output, as an increase in either will raise the total blood pumped by the heart each minute.