Cardiac Cycle Overview
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Questions and Answers

What is the total duration of the cardiac cycle if the heart rate is 90 beats/min?

  • 1.5 seconds per beat
  • 0.8 seconds per beat
  • 1.2 seconds per beat
  • 0.67 seconds per beat (correct)

    • During which phase of the cardiac cycle does the heart fill with blood?

  • Atrial systole
  • Ventricular systole
  • Atrial diastole (correct)
  • Ventricular diastole

    • If the atrial muscle cells shorten and develop tension, what event is likely to occur during the cardiac cycle?

  • Decreased atrial pressure
  • Increased ventricular contraction
  • Decreased ventricular filling
  • Increased atrial pressure (correct)

    • What percentage of blood flows directly through the atria into the ventricles even before atrial contraction at normal resting heart rates?

    <p>80%</p> Signup and view all the answers

    Which phase of the cardiac cycle is associated with the depolarization of atrial muscle cells and the appearance of the P wave on an electrocardiogram?

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

    What happens to ventricular filling during atrial systole in a normal heart?

    <p>Increases by 20%</p> Signup and view all the answers

    What plays an increasingly significant role in ventricular filling as heart rate increases?

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

    During which phase of ventricular systole does the pressure in the left ventricle continue to rise sharply?

    <p>Rapid ejection phase</p> Signup and view all the answers

    What occurs when the left ventricular pressure exceeds that in the aorta?

    <p>Opening of the aortic valve</p> Signup and view all the answers

    Which phase of ventricular systole is characterized by the chamber being a closed chamber with a fixed volume?

    <p>Isovolumetric contraction phase</p> Signup and view all the answers

    What event is represented by the QRS complex of the electrocardiogram during ventricular systole?

    <p>Contraction of ventricular muscle cells</p> Signup and view all the answers

    In which phase of ventricular systole does blood rapidly enter the aorta causing pressure to rise?

    <p>Rapid ejection phase</p> Signup and view all the answers

    What happens to the duration of each cardiac cycle when heart rate increases?

    <p>It decreases</p> Signup and view all the answers

    Why does atrial systole have to start to begin the next heart cycle?

    <p>To decrease the pressure gradient across the AV valves</p> Signup and view all the answers

    At three times the normal heart rate, what percentage of the cardiac cycle does systole comprise?

    <p>0.65</p> Signup and view all the answers

    During which phase does the aorta distend or balloons out?

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

    Why does a fast heart rate lead to incomplete filling of the cardiac chambers before the next contraction?

    <p>Decreased duration of diastole</p> Signup and view all the answers

    What effect does the reduced compliance of ventricles have on the rate of filling?

    <p>Decreases the rate of filling</p> Signup and view all the answers

    What effect does the stimulation of vagal activity have on heart rate?

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

    How do painful stimuli applied to trigger areas affect heart rate and blood pressure?

    <p>Decrease heart rate, cause vasodilation, decrease blood pressure</p> Signup and view all the answers

    What physiological variations cause the CNS ischemic response to be triggered?

    <p>Decreased blood pressure</p> Signup and view all the answers

    At what heart rate value does the CNS ischemic response result in strong activation of the sympathetic nervous system?

    <p>$60$ beats/min</p> Signup and view all the answers

    How does the SA node influence heart rate during severe emotional reactions like fear or grief?

    <p>Increases heart rate and causes vasoconstriction</p> Signup and view all the answers

    What is the role of arterial baroreceptors in the regulation of heart rate?

    <p>Decrease heart rate by sending impulses to the medulla oblongata</p> Signup and view all the answers

    Which cranial nerve supplies the carotid sinus with afferent impulses for heart rate regulation?

    <p>Glossopharyngeal nerve</p> Signup and view all the answers

    At what arterial blood pressure (ABP) do baroreceptors have maximal activity for heart rate regulation?

    <p>160 mmHg</p> Signup and view all the answers

    What is the consequence of a burst of action potentials stimulating cardiac vagal neurons at normal mean ABP?

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

    Which factor leads to rapid adjustments in baroreceptor reflexes for heart rate regulation?

    <p>Abrupt changes in peripheral resistance</p> Signup and view all the answers

    What is the main effect of vagal fibers on the SA node?

    <p>Negative chronotropic effect</p> Signup and view all the answers

    Which function is NOT associated with the sympathetic fibers' influence on the heart?

    <p>Negative dromotropic effect</p> Signup and view all the answers

    How does strong vagal activity affect the heart's conduction system?

    <p>May cause complete AV block</p> Signup and view all the answers

    At rest, which autonomic system predominantly influences heart rate?

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

    In case of blockage of both noradrenergic and cholinergic systems, what happens to heart rate?

    <p>It increases dramatically</p> Signup and view all the answers

    Which of the following physiological factors is NOT a cause of increased heart rate?

    <p>Severe emotions like fear and grief</p> Signup and view all the answers

    What is one of the causes of decreased heart rate that is NOT mentioned in the text?

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

    Which of the following is NOT influenced by the SA node in regulating heart rate?

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

    In the context provided, which factor is most likely to have a direct impact on vagal activity in regulating heart rate?

    <p>Severe pain or applied to trigger areas</p> Signup and view all the answers

    Which of the following heart rate variations is NOT typically associated with sympathetic fibers' influence?

    <p>Stimulation of atrial stretch receptors</p> Signup and view all the answers

    What is the mechanism behind the increased heart rate (HR) as a result of the Bainbridge reflex?

    <p>Increased vagal tone and decreased sympathetic tone</p> Signup and view all the answers

    How do Cardiopulmonary Mechanoreceptors respond during atrial diastole?

    <p>Decreased stretch and firing of type A receptors</p> Signup and view all the answers

    Which physiological variations would stimulate Peripheral Chemoreceptors?

    <p>Decreased PaO2 and increased PaCO2</p> Signup and view all the answers

    What effect does the release of ANP have on the blood vessels?

    <p>Promotes vasodilation in capacitance blood vessels</p> Signup and view all the answers

    What happens to ADH secretion as a result of the Cardiopulmonary Mechanoreceptors' response?

    <p>It decreases due to increased HR</p> Signup and view all the answers

    What is the role of the Rostral Ventro-Lateral Medulla (RVLM) in the regulation of blood pressure?

    <p>Sends descending fibers to spinal cord segments for sympathetic activity</p> Signup and view all the answers

    What effect does stimulation of the Vasodilator (V.D) area in the Caudal Ventro-Lateral Medulla (CVLM) have on blood pressure?

    <p>Causes generalized vasodilation</p> Signup and view all the answers

    Which area is responsible for receiving signals from different parts of the body and adjusting activities in other areas according to the effect on the heart?

    <p>Sensory area in the Nucleus Tractus Solitarius (NTS)</p> Signup and view all the answers

    Which portion of the Sensory area is responsible for transmitting excitatory impulses through sympathetic nerve fibers to the heart?

    <p>Lateral Portion</p> Signup and view all the answers

    Where do preganglionic vagal fibers arise from, according to the text?

    <p>Nucleus ambiguous in M.O.</p> Signup and view all the answers

    Which area of the medulla oblongata is responsible for controlling vasoconstriction in the cardiovascular system?

    <p>Vasoconstrictor area</p> Signup and view all the answers

    What is the function of the vasodilator area in the medulla oblongata concerning cardiovascular regulation?

    <p>Increase blood flow to active tissues</p> Signup and view all the answers

    What physiological variations can trigger the CNS ischemic response leading to strong activation of the sympathetic nervous system?

    <p>Decrease in blood flow to vital organs</p> Signup and view all the answers

    At what heart rate value does the CNS ischemic response result in strong activation of the sympathetic nervous system?

    <p>Above 100 beats/min</p> Signup and view all the answers

    How does stimulation of vagal activity influence heart rate?

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

    Which factor plays an increasingly significant role in ventricular filling as heart rate increases?

    <p>Venous return</p> Signup and view all the answers

    How does the SA node influence heart rate during severe emotional reactions like fear or grief?

    <p>Modulates heart rate through vagal activity</p> Signup and view all the answers

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