Question

In a normal person at rest, the cardiac output or amount of blood pumped per minute by the left ventricle is approximately
(A) $1-2l/min$
(B) $1l/min$
(C) $2l/min$
(D) $5l/min$

Answer 1

Hint: The heart is a vital muscular organ in a human body that circulates and pumps blood to all the parts of the body. The human heart has four chambers in the heart called ventricles and several other valves, which directs and regulates the flow of blood into the heart.

Complete answer:
The blood carries oxygen and other nutrients to all the parts of the body. The heart has to pump blood at an adequate and constant rate so that the organs get sufficient blood for their normal functioning. To support this, the heart is divided into two major halves majorly as right and left. The right side of the heart receives deoxygenated blood from the veins. It is then directed into the lungs, which oxygenates the blood and directs it to the left side of the heart, which circulates it to the rest of the body.

The cardiac output is the amount of blood that is pumped per minute by each ventricle of the heart. It is calculated using the formula,
$$\text{Cardiac output}=\text{ heart rate}\times \text{stroke volume}$$
The heart rate is the count of heartbeats in one minute. Similarly, stroke rate is the amount of blood pumped by that ventricle each time it beats.

Now let us calculate the cardiac output for the left ventricle for a person at rest.
The average heart rate at rest = $$72\text{ beats per minute}$$
The average stroke volume = $70ml$
Therefore, cardiac output =$72\times 70=5040l/min$
Thus, the cardiac output or amount of blood pumped per minute by the left ventricle is approximately $5l/min$.

Hence, the correct answer is option (D).

Note: The cardiac output can be influenced by a number of factors such as contractility, sex, preload etc. It increases three to four fold during exercise, as the muscles need more oxygen. The significance of cardiac output is that it helps in keeping the blood pressure sufficient to pump oxygenated blood to the brain and other organs.