Stroke volume The main result of the heart work is effective and enough blood injection from the ventricles in the pulmonary and systemic circulation

Heart pump [function]

Stroke volume

The main result of the heart work is effective and enough blood injection from the ventricles in the pulmonary and systemic circulations of blood to provide organs and tissues with oxygen and nutrients under various conditions of human life. In a state of physical and emotional rest at a heart rate of 60-85 beats per minute (in adult) during one contraction every ventricle ejects 65-75 ml of blood; this is a stroke volume of blood (SV).

Cardiac output

An important indicator of heart pumping is the minute volume of blood also called the cardiac output (CO). It is the same for both ventricles. It is determined by the formula: CO = HR • SV where CO — is a cardiac output, HR — heart rate, SV — stroke volume of blood.

In a state of physical and emotional rest at normal amounts of heart rate and stroke volume of blood, a minute volume of blood is 4-5 liters per minute. When physical exertion (lesser extent — emotional), minute volume of blood increases and can reach 25-30 liters. Taken from http://worldofschool.org

In untrained humans, the cardiac output increases due to an increase of heart rate. This heart mode is not economical because it is accompanied by high energy costs. A trained human heart rate also increases, but the cardiac output increases mainly due to more economical, in terms of energy consumption, mechanism — to enhance the strength of heart contractions, i.e. to increase the stroke volume. With intense physical exertion, the stroke volume of blood can increase to 100-120 ml, and heart rate — up to 150-200 beats per minute.

In people with heart disease violated its pumping function: reduces strength of myocardial contractions, stroke volume and cardiac output. A heart failure occurs — a condition of the heart's inability to ensure adequate blood supply to organs and tissues.

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Questions:
  • Explain the mechanism of heart pumping.

  • What is an important indicator of heart pumping?