Lecture 2.2a - Control of cardiac output
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Questions and Answers

What is the primary factor that determines the sinus rhythm of the heart?

  • AV node
  • Bundle of His
  • SA node (correct)
  • Purkinje fibres
  • What is the effect of increased Ca2+ levels on heart rate?

  • Increased heart rate (correct)
  • Heart rate remains constant
  • Decreased heart rate
  • No effect on heart rate
  • What is the term for a heart rate greater than 100bpm?

  • Tachycardia (correct)
  • Hypertension
  • Arrhythmia
  • Bradycardia
  • What is the formula to calculate cardiac output?

    <p>Heart rate x stroke volume</p> Signup and view all the answers

    What is the normal cardiac output at rest?

    <p>5L/minute</p> Signup and view all the answers

    Which of the following is a factor that decreases heart rate?

    <p>Parasympathetic nervous system</p> Signup and view all the answers

    What is the formula to calculate stroke volume?

    <p>EDV - ESV</p> Signup and view all the answers

    What is the term for the amount of stretch of the ventricles at the end of diastole?

    <p>Preload</p> Signup and view all the answers

    Study Notes

    Cardiac Output

    • Cardiac output is the amount of blood pumped from the right or left ventricles per minute, calculated by multiplying heart rate and stroke volume.
    • At rest, cardiac output is approximately 5L/minute, increasing to around 25L/minute during exercise.
    • The cardiac output should meet the body's demand for oxygen and nutrients.

    Heart Rate

    • The average heart rate in a healthy adult is 60-80 beats per minute (bpm).
    • The sinoatrial (SA) node sets the sinus rhythm, which can be influenced by various factors.
    • Factors that increase heart rate (positive chronotropic): • Sympathetic nervous system (adrenaline/noradrenaline) signals • Hormones (T3, T4) increasing metabolism • Body temperature • Increased Ca2+ levels • Hypoxia and hypercapnia (low oxygen and high carbon dioxide)
    • Tachycardia is a heart rate above 100bpm, while bradycardia is a heart rate below 60bpm.
    • Factors that decrease heart rate (negative chronotropic): • Parasympathetic nervous system (acetylcholine) signals • Hyperkalaemia (increased K+ levels) • Decreased Ca2+ levels

    Stroke Volume

    • Stroke volume is the amount of blood pumped from the left or right ventricles per beat, calculated by subtracting end-systolic volume (ESV) from end-diastolic volume (EDV).
    • The stroke volume is influenced by three factors: • Preload: • Amount of stretch of the ventricles at the end of diastole (EDV) • Factors that alter preload: - Venous return - Skeletal muscle pump - Respiratory pump - Venous tone - Gravity • Contractility: • The Frank-Starling Law, which states that the more the heart stretches, the more it contracts.

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    Description

    Learn about cardiac output, heart rate, and factors that influence them, including the role of the sympathetic nervous system.

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