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The Cardiovascular System

Stroke volume, cardiac output and the trained heart

  • 3 things to know
  • A2 2

Overview

Stroke volume, ejection fraction and Starling's law, cardiac output and heart rate calculations, the stroke volume plateau, trained and untrained hearts, endurance and strength hearts and resting heart rate.

What you need to know

Answer each one before you reveal it.

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Key term

What is stroke volume, and what is a typical resting value?

Numbers

A ventricle holds 130 ml at the end of diastole and 60 ml at the end of systole. Calculate the stroke volume.

Key term

What is the ejection fraction, and what is it for a stroke volume of 70 ml from an end-diastolic volume of 130 ml?

Questions from this subtopic

Each one with the model answer underneath.

  1. 1

    What is stroke volume, and what is a typical resting value?

    Model answer

    Stroke volume is the volume of blood ejected from the left ventricle in one beat. Resting stroke volume is about 70 ml in an untrained adult.

  2. 2

    A ventricle holds 130 ml at the end of diastole and 60 ml at the end of systole. Calculate the stroke volume.

    Model answer

    The stroke volume is 70 ml. The working is end-diastolic volume minus end-systolic volume, 130 − 60 = 70 ml.

  3. 3

    What is the ejection fraction, and what is it for a stroke volume of 70 ml from an end-diastolic volume of 130 ml?

    Model answer

    The ejection fraction is the percentage of the blood in the ventricle that is pumped out in each beat. The ejection fraction here is about 54%, because 70 ÷ 130 = 0.538.

  4. 4

    Explain Starling's law of the heart.

    Model answer

    Greater venous return stretches the ventricle walls further as they fill. The stretched cardiac muscle contracts more forcefully, raising stroke volume.

  5. 5

    What is cardiac output, and how is it calculated?

    Model answer

    Cardiac output is the volume of blood pumped out of the left ventricle each minute. Cardiac output equals stroke volume multiplied by heart rate.

  6. 6

    What is heart rate, and what is a typical resting value?

    Model answer

    Heart rate is the number of times the heart beats each minute. A typical adult resting heart rate is about 72 beats per minute.

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AThe target heart rate is about 168 bpm.
BMaximum heart rate is 220 − 18 = 202 bpm.
CThe working is 0.75 × (202 − 65) + 65 = 167.75 bpm.

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