Cardiac Muscle Physiology
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Questions and Answers

What happens at 0mV in the cardiac action potential?

  • Both Ca++ channels close and K+ channels open (correct)
  • K+ channels close
  • Ca++ channels open
  • Both Ca++ channels open and K+ channels close
  • What role do slow Ca++ channels play in the cardiac action potential?

  • Maintaining the resting membrane potential
  • Causing hyperpolarization
  • Allowing for the plateau phase (correct)
  • Initiating depolarization
  • If not for endocrine control, how many times per minute would the SA node fire?

  • 50 - 70 times
  • 80 - 90 times (correct)
  • 120 - 130 times
  • 100 - 110 times
  • Which component of the heart's conduction system has the lowest firing rate?

    <p>Purkinje fibers</p> Signup and view all the answers

    What is another term used to refer to recording electrical signals of the heart?

    <p>ECG or EKG</p> Signup and view all the answers

    What event marks the depolarization of the ventricles in the cardiac cycle?

    <p>QRS complex</p> Signup and view all the answers

    What is the function of the atria in the heart?

    <p>Collect blood and push it into the lower chambers</p> Signup and view all the answers

    Which device is designed to correct fibrillations in the heart?

    <p>Artificial pacemaker</p> Signup and view all the answers

    Where is the base of the heart located?

    <p>Superior and medial to the apex</p> Signup and view all the answers

    What represents the amount of blood pushed out by the ventricles in one cycle?

    <p>Stroke volume</p> Signup and view all the answers

    Which artery carries deoxygenated blood?

    <p>Pulmonary artery</p> Signup and view all the answers

    What occurs during ventricular diastole in the cardiac cycle?

    <p>Semilunar valves open</p> Signup and view all the answers

    Where is the myocardium located in the heart?

    <p>Middle thickest layer with muscle cells and blood vessels</p> Signup and view all the answers

    What signifies the interruption in the normal conduction pathway of the heart?

    <p>Heart block</p> Signup and view all the answers

    What is the purpose of the serous pericardium layer in the heart?

    <p>Produce lubricating fluid</p> Signup and view all the answers

    During which phase of the cardiac cycle does blood flow into the atria and through into the ventricles?

    <p>Atrial diastole</p> Signup and view all the answers

    What are auricles in the heart?

    <p>Thin walled structures that hold blood and empty into atria</p> Signup and view all the answers

    Which heart sound is heard at the closing of the atrioventricular valves?

    <p>S1</p> Signup and view all the answers

    What is the cause of heart murmurs?

    <p>Turbulent blood flow</p> Signup and view all the answers

    What is the equation for Cardiac Output (CO)?

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

    What does the ejection fraction represent?

    <p>Percentage of blood pumped in each heartbeat</p> Signup and view all the answers

    What happens to Stroke Volume (SV) as heart rate increases during exercise?

    <p>SV decreases proportionally</p> Signup and view all the answers

    What is the normal range for Ejection Fraction (EF)?

    <p>50% - 70%</p> Signup and view all the answers

    Which layer lines the chambers filled with blood and covers the heart valves?

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

    What is the function of endothelins released by the endothelium?

    <p>Regulate growth patterns of cardiac muscle cells</p> Signup and view all the answers

    What is the function of the septum in the heart?

    <p>Separates atria from ventricles</p> Signup and view all the answers

    Which chamber of the heart receives deoxygenated blood from the systemic circulation?

    <p>Right atrium</p> Signup and view all the answers

    What purpose do semilunar valves serve in the heart?

    <p>Separate ventricles from blood vessels</p> Signup and view all the answers

    Which structure connects chordae tendineae to close the mitral valve in the heart?

    <p>Papillary muscles</p> Signup and view all the answers

    What is the function of coronary circulation in the body?

    <p>Deliver oxygenated blood to organs</p> Signup and view all the answers

    Plateau phase in cardiac contractile cells involves which of the following ion channels?

    <p>$Na^+$ channels close, $Ca^{++}$ channels are open, few K$^+$ channels are open</p> Signup and view all the answers

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