Question Video: Calculating Cardiac Output from Stroke Volume and Heart Rate | Nagwa Question Video: Calculating Cardiac Output from Stroke Volume and Heart Rate | Nagwa

# Question Video: Calculating Cardiac Output from Stroke Volume and Heart Rate Biology • Second Year of Secondary School

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Calculate the cardiac output in cm³/min of a heart that has a stroke volume of 80 cubic centimeters per beat and a heart rate of 70 bpm, to the nearest whole number.

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### Video Transcript

Calculate the cardiac output in centimeter cubed per minute of a heart that has a stroke volume of 80 cubic centimeters per beat and a heart rate of 70 beats per minute, to the nearest whole number.

This question asks us to calculate the cardiac output from stroke volume and beats per minute. Let’s review these terms in order to answer our question correctly.

Cardiac output refers to the volume of blood pumped by the heart in one minute. This is an important number that doctors will look at in order to determine how well the heart is functioning. The heart is responsible for pumping the blood around the body. This is important as blood carries oxygen and nutrients to all the body cells and carries away carbon dioxide and other waste products from cells.

In order to calculate cardiac output, we can use the following equation: cardiac output equals stroke volume times heart rate. Here, stroke volume refers to the volume of blood pumped in one beat of the heart. You might remember that volume can be expressed as cubic centimeters or milliliters. In our question, stroke volume is in cubic centimeters. Heart rate, on the other hand, is the number of times a heart beats per minute. A normal heart rate is between 60 and 100 beats per minute, represented as bpm.

You can calculate your own heart rate by finding your pulse, then counting the number of times your heart beats in 15 seconds, and multiplying this number by four. Some people can feel their pulse on their wrist, while others will count the number of beats from the pulse felt in their neck.

Now that we have discussed stroke volume and heart rate, we are able to plug these values into our equation. Here, the following equation should read, “Cardiac output is equal to 80 centimeters cubed per beat multiplied by 70 beats per minute.” Per beat means divided by beat, so it can be written like this. And per minute means divided by minutes, so it can be written like this. You might notice that in our units, we have beats in both the numerator and the denominator. Therefore, the unit beats cancels out. Now, we are left with centimeters cubed over minutes.

In order to calculate our numerical value, we can either use a calculator or do an easy trick. The product of eight times seven is equal to 56. Because the numbers 80 and 70 both contain one zero each, we need to add two zeros to the end of 56. So, the correct answer should be 5,600. After working through this problem, we know that the cardiac output is 5,600 centimeters cubed per minute.

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