Cardiac Cycle and Heart Sounds
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During which phase of the cardiac cycle does the pressure in the ventricles rise above the pressure in the arteries, causing the semilunar valves to open?

  • Isovolumic ventricular relaxation
  • Atrial systole
  • Isovolumic ventricular contraction
  • Ventricular ejection (correct)

    • What is the significance of the 'S1' heart sound?

  • It marks the opening of the atrioventricular valves.
  • It marks the closure of the semilunar valves.
  • It marks the opening of the semilunar valves.
  • It marks the closure of the atrioventricular valves. (correct)

    • What happens to the volume of blood in the ventricle during the isovolumic ventricular contraction phase?

  • Volume increases due to blood entering from the atria
  • Volume fluctuates as semilunar valves open and close.
  • Volume remains constant as all valves are closed (correct)
  • Volume decreases as blood is ejected into the arteries

    • According to the provided information on the cardiac cycle, what does the term 'diastole' refer to?

    <p>The period of relaxation for both atria and ventricles (B)</p> Signup and view all the answers

    Based on the description of the pressure-volume curve, what does the point 'B' on the curve represent?

    <p>The end of atrial contraction (B)</p> Signup and view all the answers

    On which axis of the pressure-volume curve would you find the volume of blood in the ventricle?

    <p>The horizontal axis (B)</p> Signup and view all the answers

    Which of these events would cause the pressure in the ventricle to increase most significantly?

    <p>Isovolumic ventricular contraction (D)</p> Signup and view all the answers

    What does the 'end-diastolic volume' refer to in the context of the cardiac cycle?

    <p>The volume of blood in the ventricle at the end of diastole (C)</p> Signup and view all the answers

    What primary factor determines the force of ventricular contraction according to the Frank-Starling Law?

    <p>End-diastolic volume (C)</p> Signup and view all the answers

    Which of the following describes the role of norepinephrine in cardiac muscle contraction?

    <p>It increases the force of contraction by enhancing calcium interaction (A)</p> Signup and view all the answers

    Inotropic agents affect the heart's contractility. Which of the following would be classified as an inotropic agent?

    <p>Norepinephrine (A)</p> Signup and view all the answers

    Which mechanism is primarily responsible for the increase in force of contraction due to norepinephrine?

    <p>Increased calcium release from the sarcoplasmic reticulum (A)</p> Signup and view all the answers

    How does venous return influence stroke volume?

    <p>Increases stroke volume as more blood returns to the heart (A)</p> Signup and view all the answers

    What happens to the left ventricular pressure during atrial systole?

    <p>It slightly increases. (C)</p> Signup and view all the answers

    At which point does the left ventricular pressure reach its peak?

    <p>Just after the aortic valve opens. (B)</p> Signup and view all the answers

    What occurs during isovolumetric contraction?

    <p>Pressure is building while all valves are closed. (A)</p> Signup and view all the answers

    What event occurs immediately after the tricuspid valve closes?

    <p>The ventricle undergoes isovolumetric contraction. (B)</p> Signup and view all the answers

    Which phase follows ventricular systole?

    <p>Ventricular diastole. (B)</p> Signup and view all the answers

    What primarily causes the pressure increase in the ventricle during atrial systole?

    <p>Blood volume from atrial contraction. (B)</p> Signup and view all the answers

    During which phase does the tricuspid valve open?

    <p>Early ventricular diastole. (C)</p> Signup and view all the answers

    Where in the cycle is the left ventricular pressure at its lowest?

    <p>At the end of ventricular diastole. (A)</p> Signup and view all the answers

    What is the relationship between pressure and volume in the ventricle during ventricular systole?

    <p>Pressure increases while volume remains constant. (A)</p> Signup and view all the answers

    Which of the following correctly describes the end of atrial systole?

    <p>The ventricle begins to contract. (B)</p> Signup and view all the answers

    What is the measurement of stroke volume based on?

    <p>End-diastolic volume minus end-systolic volume (A)</p> Signup and view all the answers

    What does the dicrotic notch in the aortic pressure curve represent?

    <p>The closure of the aortic valve (D)</p> Signup and view all the answers

    During which phase is the aortic pressure increasing?

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

    Which heart sound corresponds with the closure of the tricuspid valve?

    <p>S1 (D)</p> Signup and view all the answers

    What information does the QRS complex provide in an ECG?

    <p>Ventricular depolarization (A)</p> Signup and view all the answers

    How is cardiac output calculated?

    <p>Heart rate multiplied by stroke volume (A)</p> Signup and view all the answers

    What phase immediately follows isovolumetric contraction in the cardiac cycle?

    <p>Ejection phase (D)</p> Signup and view all the answers

    During early ventricular diastole, what happens to the left ventricular volume?

    <p>Increases significantly (D)</p> Signup and view all the answers

    What occurs during atrial systole?

    <p>Atrial pressure rises due to contraction (C)</p> Signup and view all the answers

    Which phase signifies the end of passive ventricular filling?

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

    What characterizes isovolumic contraction in the cardiac cycle?

    <p>Pressure rises without any change in volume. (C)</p> Signup and view all the answers

    Which of the following describes afterload?

    <p>The pressure against which the ventricles must contract (B)</p> Signup and view all the answers

    What occurs during the D to A phase of the pressure-volume curve?

    <p>The ventricle is in isovolumic relaxation. (A)</p> Signup and view all the answers

    What happens to left ventricular pressure during isovolumetric relaxation?

    <p>It decreases gradually (D)</p> Signup and view all the answers

    What is the function of stroke volume (SV) in the cardiac cycle?

    <p>It indicates the volume of blood ejected from the ventricle per beat. (B)</p> Signup and view all the answers

    What causes the first heart sound (S1) during the cardiac cycle?

    <p>Closure of the mitral and tricuspid valves. (B)</p> Signup and view all the answers

    Which phase is characterized by the ventricles contracting while all valves are closed?

    <p>Isovolumetric contraction (C)</p> Signup and view all the answers

    What is the average cardiac output for a healthy adult?

    <p>5 L/min (B)</p> Signup and view all the answers

    Which phase follows atrial depolarization represented by the P wave in an ECG?

    <p>Atrial contraction occurs. (B)</p> Signup and view all the answers

    What describes the dicrotic notch observed in the cardiac cycle?

    <p>It is due to the closure of semilunar valves. (D)</p> Signup and view all the answers

    What occurs during the isovolumic relaxation phase?

    <p>Both aortic and mitral valves are closed. (B)</p> Signup and view all the answers

    During ventricular diastole, what is happening in the heart?

    <p>Both ventricles are passively filling with blood. (C)</p> Signup and view all the answers

    How does pressure in the left atrium change during atrial systole?

    <p>It increases. (C)</p> Signup and view all the answers

    What is indicated by the QRS complex in an ECG?

    <p>Ventricular contraction. (B)</p> Signup and view all the answers

    What can be inferred about left ventricular volume during isovolumic contraction?

    <p>It remains unchanged. (D)</p> Signup and view all the answers

    What does the T wave in an ECG represent?

    <p>Ventricular repolarization. (C)</p> Signup and view all the answers

    What changes follow the closure of the aortic valve?

    <p>Isovolumic relaxation begins. (A)</p> Signup and view all the answers

    What happens to atrial pressure during ventricular systole?

    <p>It increases slightly due to blood backflow. (C)</p> Signup and view all the answers

    During isovolumetric contraction, what is the primary reason for the pressure increase within the ventricle?

    <p>The volume of blood in the ventricle remains constant, and the ventricle contracts. (A)</p> Signup and view all the answers

    What event marks the onset of diastole?

    <p>Closure of the aortic valve. (C)</p> Signup and view all the answers

    What is the primary contributor to the pressure drop in the aorta during diastole?

    <p>The blood flowing from the arteries into the venous system. (D)</p> Signup and view all the answers

    What is the significance of the 'dicrotic notch' observed on the aorta pressure curve?

    <p>It signifies the closure of the aortic valve, preventing blood backflow. (D)</p> Signup and view all the answers

    What is the primary difference between 'isovolumetric contraction' and 'ventricular ejection'?

    <p>Isovolumic contraction involves all four valves being closed, while ejection involves the aortic valve opening. (D)</p> Signup and view all the answers

    During what phase of the cardiac cycle does the left atrial pressure exceed the left ventricular pressure?

    <p>Atrial systole. (C)</p> Signup and view all the answers

    Why is the pressure in the left ventricle higher than that in the left atrium during isovolumetric contraction?

    <p>The ventricle is actively contracting, while the atria are relaxed. (B), The mitral valve is closed, preventing blood backflow from the ventricle to the atrium. (D)</p> Signup and view all the answers

    What does the QRS complex on the ECG indicate?

    <p>The ventricles are depolarizing and starting to contract. (D)</p> Signup and view all the answers

    What event usually happens shortly after the QRS complex on the ECG?

    <p>Closure of the mitral valve. (C)</p> Signup and view all the answers

    During which phase of the cardiac cycle is the left ventricular volume constant?

    <p>Isovolumic contraction. (A), Isovolumic relaxation. (B)</p> Signup and view all the answers

    Which statement(s) correctly explain why the pressure in the aorta drops during diastole?

    <p>The blood is slowly displaced from the arterial circulation into the venous circulation. (A), The aortic valve closes, preventing backflow of blood from the aorta into the ventricle. (D)</p> Signup and view all the answers

    Which event is responsible for the sudden increase in left ventricular volume during atrial systole?

    <p>The mitral valve opens, allowing blood to flow from the atrium into the ventricle. (D)</p> Signup and view all the answers

    What is the primary reason for the slight increase in left atrial pressure immediately before the opening of the tricuspid valve?

    <p>The atrium is contracting, increasing its pressure. (B)</p> Signup and view all the answers

    During which phase of the cardiac cycle is the heart muscle completely unable to be stimulated further?

    <p>Early ventricular diastole. (C)</p> Signup and view all the answers

    Which of the following statements correctly describes the relationship between ventricular pressure and aortic pressure during ventricular ejection?

    <p>Ventricular pressure is always higher than aortic pressure during ejection. (B)</p> Signup and view all the answers

    What is the main reason for the pressure “flip” observed during isovolumetric relaxation?

    <p>Opening of the mitral valve. (A)</p> Signup and view all the answers

    Study Notes

    Cardiac Cycle, Cardiac Output, Stroke Volume and Heart Rate

    • The cardiac cycle describes the sequence of events in one heartbeat
    • Cardiac output is the volume of blood pumped by one ventricle per minute
    • Stroke volume (SV) is the volume of blood pumped by one ventricle with each contraction
    • Heart rate (HR) is the number of heartbeats per minute

    Definitions for Systole and Diastole

    • Systole: Contraction phase of the heart muscle
    • Diastole: Relaxation phase of the heart muscle
    • Atrial systole: Contraction of the atria, pumping blood into the ventricles
    • Atrial diastole: Relaxation of the atria, allowing them to fill with blood
    • Ventricular systole: Contraction of the ventricles, pumping blood out of the heart
    • Ventricular diastole: Relaxation of the ventricles, allowing them to fill with blood

    Pressure-Volume Curve (Loop)

    • Represents changes in volume and pressure during one cardiac cycle
    • Pressure is measured on the Y-axis
    • Volume is measured on the X-axis
    • Shows the relationship between pressure and volume as the heart goes through systole and diastole

    Pressure-Volume Curve (Left Ventricle)

    • The graph shows the relationship between left ventricular pressure and volume during one complete cardiac cycle.
    • EDV (End-Diastolic Volume) is the volume of blood in the left ventricle at the end of diastole
    • ESV (End-Systolic Volume) is the volume of blood remaining in the left ventricle at the end of systole
    • Stroke Volume (SV) is the difference between EDV and ESV
    • A to A': Isometric ventricular relaxation
    • A to B: Ventricular filling and atrial contraction, increasing volume
    • B to C: Isovolumic ventricular contraction, pressure increases without change in volume
    • C to D: Ventricular ejection, pressure rises causing ejection of blood, and stroke volume
    • D to A: Isovolumic ventricular relaxation, ventricles relax without change in volume

    Normal Heart Sounds

    • Sounds generated by the heart that can be heard with a stethoscope
    • First heart sound (S1) occurs during the start of ventricular systole when the mitral and tricuspid valves close.
    • Second heart sound (S2) occurs at the start of ventricular diastole when the aortic and pulmonary valves close.

    Putting Everything Together (Cardiac Cycle)

    • Graph shows the ECG (Electrocardiogram), blood pressure, and heart sounds across one cycle.
    • Each stage of the cycle is correlated with related ECG, pressure, and sound

    Heart Rate

    • Normal resting heart rate: 60-100 bpm
    • Initiated by autorhythmic cells
    • Sympathetic NS activation increases HR by increasing rate of depolarization
    • Parasympathetic NS activation decreases HR by increasing K+ efflux

    What Factors Influence Stroke Volume?

    • 1) Length of the muscle fibers: Ability of muscle fibers to contract is directly related to the length of the fiber. The more the muscle stretches, the stronger the contraction
    • 2) Contractility: Intrinsic ability of the cardiac muscle fiber to contract; determined by intracellular calcium levels.
    • 3) Venous return: Amount of blood returning to the heart from the veins
    • 4) Skeletal muscle: Contraction of skeletal muscle around the veins pushes blood back to the heart, increasing venous return
    • 5) Respiratory pump: When you breathe in, pressure in the lungs decreases, which decreases pressure in the veins of the lungs, increasing the amount of blood flowing through them and back to the heart.
    • Frank-Starling Law: SV is proportional to end-diastolic volume (EDV).

    Norepinephrine: Effect on Contractility

    • Norepinephrine increases force of contraction, increasing stroke volume.
    • Norepinephrine binds to beta-1 receptors, activating secondary messengers that enhance calcium interaction, increasing contractility and stroke volume.

    Other Factors that Affect Stroke Volume

    • Venous return: The total volume of blood returning to the heart from venous circulation. Higher venous return leads to a higher EDV and potentially a higher SV.
    • Skeletal muscle contraction: Contraction of skeletal muscles compresses veins, promoting venous return and thereby increasing SV.
    • Respiration: Changes in intrathoracic pressure during breathing (the respiratory pump) also help to circulate blood back to the heart, thereby increasing venous return.

    Cardiac Output and Stroke Volume

    • Cardiac output (CO) is calculated by multiplying heart rate (HR) by stroke volume (SV): CO = HR x SV
    • Average stroke volume (SV) is 70 mL/beat
    • Average cardiac output (CO) is approximately 5 L/minute

    Quiz Questions

    • Answers for the quiz questions are not included in the notes.

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    Lecture 7 - Cardiac Cycle, Factors Affecting Cardiac Output, Stroke Volume & Heart Rate - PDF

    Description

    This quiz explores the cardiac cycle, focusing on phases like isovolumic contraction and diastole. It also delves into the significance of heart sounds, pressure-volume curves, and factors impacting ventricular contraction. Test your understanding of these concepts and their relevance to cardiovascular physiology.

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