Cardiac Output and Factors Influencing Heart Rate
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Questions and Answers

What is the formula to calculate stroke volume?

  • HR x CO
  • CO + HR
  • EDV - ESV (correct)
  • HR / CO

    • Which factor influences preload?

  • Venous Return (correct)
  • Sympathetic Nervous System
  • Afterload
  • Contractility

    • What happens to stroke volume when contractility decreases?

  • It remains the same
  • Decreases (correct)
  • Becomes negative
  • Increases

    • Which factor influences stroke volume by increasing the force of muscle contraction?

    <p>Starlings Law</p> Signup and view all the answers

    What does afterload refer to in the context of cardiac output?

    <p>Force ventricles must overcome to eject blood</p> Signup and view all the answers

    Which nervous system influences heart rate to slow down?

    <p>Parasympathetic Nervous System</p> Signup and view all the answers

    During which phase of the cardiac cycle do the ventricles contract and build up pressure to open the semilunar valves?

    <p>Isovolumetric Contraction</p> Signup and view all the answers

    What is the approximate amount of blood that pumps from each ventricle during ventricular ejection?

    <p>70 ml</p> Signup and view all the answers

    Which valve must be closed during isovolumetric relaxation?

    <p>Aortic Semilunar Valve</p> Signup and view all the answers

    What factor contributes to passive filling of the ventricles?

    <p>Force of Gravity</p> Signup and view all the answers

    Which formula is used to calculate Cardiac Output (CO)?

    <p>$CO = SV imes HR$</p> Signup and view all the answers

    What does Stroke Volume (SV) represent in the context of Cardiac Output?

    <p>Volume of blood pumped by the heart in one beat</p> Signup and view all the answers

    Which node is slower than the SA node and is located posterior and medial to the tricuspid valve?

    <p>Atrioventricular node (AV node)</p> Signup and view all the answers

    What is the role of a pacemaker in case of SA node misfiring?

    <p>To regulate the heart rate</p> Signup and view all the answers

    What happens to the heart rate if the AV node fails to function properly?

    <p>Heart rate drops to 20 beats per minute</p> Signup and view all the answers

    Which type of fibrillation is life-threatening and manifests as chaotic activity on an EKG tracing?

    <p>Ventricular fibrillation</p> Signup and view all the answers

    What is the clinical significance of a T wave in an EKG reading?

    <p>Depolarization repolarization</p> Signup and view all the answers

    Which node is responsible for picking up the pace if both the SA node and the AV node fail?

    <p>Bundle branch</p> Signup and view all the answers

    Study Notes

    Cardiac Output and Stroke Volume

    • The formula to calculate stroke volume is: SV = EDV - ESV, where EDV is end-diastolic volume and ESV is end-systolic volume.
    • Preload is influenced by the volume of blood in the ventricles, also known as end-diastolic volume.
    • When contractility decreases, stroke volume decreases.
    • Contractility is increased by sympathetic stimulation, which increases the force of muscle contraction and thus influences stroke volume.

    Cardiac Cycle and Valves

    • During the systolic phase of the cardiac cycle, the ventricles contract and build up pressure to open the semilunar valves.
    • Approximately 70 ml of blood is pumped from each ventricle during ventricular ejection.
    • The mitral valve must be closed during isovolumetric relaxation.

    Cardiac Output and Filling

    • The formula to calculate Cardiac Output (CO) is: CO = HR x SV, where HR is heart rate and SV is stroke volume.
    • Stroke Volume (SV) represents the amount of blood pumped by the heart per beat.
    • Gravity and suction of the ventricles contribute to passive filling of the ventricles.

    Electroconduction and Pacemakers

    • The AV node is slower than the SA node and is located posterior and medial to the tricuspid valve.
    • A pacemaker takes over the pacing function if the SA node misfires or fails.
    • If the AV node fails to function properly, the heart rate slows down.
    • The AV node can take over the pacing function if both the SA node and the AV node fail.

    Arrhythmias and EKG

    • Ventricular fibrillation is a life-threatening arrhythmia that manifests as chaotic activity on an EKG tracing.
    • A T wave in an EKG reading indicates ventricular repolarization, which is important for diagnosing cardiac conditions.
    • The Bundle of His is responsible for picking up the pace if both the SA node and the AV node fail.

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    Description

    This quiz covers the concept of cardiac output, stroke volume, and factors that influence heart rate. Topics include calculating stroke volume, understanding cardiac output, and the role of the sympathetic and parasympathetic nervous systems in regulating heart rate.

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