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Cardiac Revolution Overview
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Cardiac Revolution Overview

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Questions and Answers

What initiates the process of ventricular systole?

  • Increase in end-diastolic volume
  • Relaxation of the cardiac muscle
  • Closure of the atrioventricular valves (correct)
  • Opening of the atrioventricular valves

    • What happens during the diastole phase of the cardiac cycle?

  • The A-V valves open and close simultaneously
  • The heart's electrical signals are generated
  • The ventricles fill with blood (correct)
  • Blood is ejected from the ventricles

    • What happens to the residual volume as the force of contraction increases?

  • It remains constant.
  • It fluctuates unpredictably.
  • It increases significantly.
  • It decreases. (correct)

    • What effect does a lower resting heart rate in trained athletes have on cardiac output during exercise?

    <p>Increases cardiac output adaptation</p> Signup and view all the answers

    When does aortic valve closure occur in relation to left ventricular pressure?

    <p>When LV Pressure &lt; Ao Pressure.</p> Signup and view all the answers

    During isovolumetric relaxation, what happens to the atrial pressure?

    <p>It drops rapidly.</p> Signup and view all the answers

    What is the relationship between heart rate and end-diastolic volume?

    <p>It decreases after a maximum heart rate is reached</p> Signup and view all the answers

    Which phase occurs first during the ventricular systole process?

    <p>Iso-volumetric ventricular contraction</p> Signup and view all the answers

    What causes the closure of the sigmoid valves?

    <p>Small reflux of blood towards the ventricle.</p> Signup and view all the answers

    What characterizes prolonged tachycardia?

    <p>Progresses to heart failure</p> Signup and view all the answers

    What does the aortic pressure rebound indicate about the aorta?

    <p>It demonstrates the quality of aortic elasticity.</p> Signup and view all the answers

    What occurs during iso-volumetric relaxation?

    <p>A-V valves close while sigmoid valves remain closed</p> Signup and view all the answers

    How do cardiac pressures vary during the cardiac cycle?

    <p>They vary between systole and diastole.</p> Signup and view all the answers

    What condition produces the dicrotic wave seen in aortic pressure?

    <p>Elastic rebound of the aorta.</p> Signup and view all the answers

    What primarily regulates the SV/DV variation?

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

    What characterizes the pulmonary pressure curve compared to the aortic pressure curve?

    <p>It is identical but with lower values.</p> Signup and view all the answers

    What heart sound is produced by the closure of the A-V valves?

    <p>B1</p> Signup and view all the answers

    Which of the following heart sounds is not audible through auscultation?

    <p>B3</p> Signup and view all the answers

    What is the primary cause of cardiac work (W) as described in the content?

    <p>Pressure difference and volume difference</p> Signup and view all the answers

    During which condition does cardiac output increase significantly?

    <p>During exercise</p> Signup and view all the answers

    What does the term 'pre-load' refer to in the context of cardiac physiology?

    <p>The tension in cardiac muscle at the start of contraction</p> Signup and view all the answers

    What is a characteristic feature of heart murmurs?

    <p>They indicate aortic valve incompetence.</p> Signup and view all the answers

    What physiological event generates the B2 heart sound?

    <p>Sigmoid valve closure</p> Signup and view all the answers

    What does the Frank-Starling mechanism indicate about the relationship between cardiac muscle fiber length and contraction force?

    <p>Longer fibers lead to increased contraction force.</p> Signup and view all the answers

    What is the formula for Stroke Volume (SV)?

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

    Which factor does NOT directly affect end systolic volume (ESV)?

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

    During which physiological condition is cardiac output (Qc) expected to increase the most?

    <p>Physical exercise</p> Signup and view all the answers

    What relationship exists between preload (VTD) and contractility in terms of intracellular Ca2+ availability?

    <p>Increased preload enhances Ca2+ availability.</p> Signup and view all the answers

    What is the normal cardiac output (Qc) for an adult male at rest?

    <p>5-6 l/min</p> Signup and view all the answers

    Which statement accurately describes the role of afterload in cardiac function?

    <p>It is the load against which the ventricle must contract.</p> Signup and view all the answers

    What does the cardiac index measure?

    <p>Cardiac output in relation to body surface area.</p> Signup and view all the answers

    Which condition is NOT a cause of low cardiac output of cardiac origin?

    <p>Chronic Obstructive Pulmonary Disease (COPD)</p> Signup and view all the answers

    What is primarily measured using the Fick method?

    <p>The difference in oxygen concentration</p> Signup and view all the answers

    Which factor is responsible for high cardiac output in cases of anemia?

    <p>Reduced blood viscosity</p> Signup and view all the answers

    What does the term 'arterio-venous difference' refer to in the context of the Fick method?

    <p>Difference in oxygen levels between arteries and veins</p> Signup and view all the answers

    What is a disadvantage of the Echo-Doppler method for measuring cardiac output?

    <p>It provides low accuracy due to variability</p> Signup and view all the answers

    What is the principle behind thermodilution as a method for measuring cardiac output?

    <p>It monitors temperature changes after injecting cold saline</p> Signup and view all the answers

    Which of the following substances is commonly used for dilution indicators in cardiac output measurement?

    <p>131I-labeled plasma albumin</p> Signup and view all the answers

    In acute venous vasodilatation leading to low cardiac output, what is primarily affected?

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

    Study Notes

    Cardiac Revolution Overview

    • The heart functions as a pump through two phases: systole (contraction) and diastole (relaxation).
    • A cardiac cycle consists of electrical and mechanical phenomena.
    • Systole: Involves the contraction of ventricles and ejection of blood.
    • Diastole: Involves relaxation and filling of the ventricles.
    • The cardiac revolution is the time between successive heart contractions.
    • Under normal heart rates, ventricular diastole lasts longer than ventricular systole.
    • Flow increases with increasing heart rate, peaking at a maximum age-dependent frequency (220 - age).
    • Trained athletes adapt better to exercise with lowered resting heart rates.

    Ventricular Systole

    • Initiates with closure of the atrioventricular (A-V) valves.
    • Comprises two parts:
      • Iso-volumetric contraction: Ventricles contract without changing volume.
      • Systolic ejection: Blood is expelled into the aorta and pulmonary artery, concluding when the sigmoid valves close.

    Ventricular and General Diastole

    • Begins with the closure of the sigmoid valves; consists of four stages:
      • Iso-volumetric relaxation: Valves closed, cardiac muscle relaxes, and residual volume is impacted by contraction strength.
    • Aortic valve closes when left ventricular (LV) pressure falls below aortic pressure (approximately 80 mmHg).
    • During this phase, mitral atrial pressure rises due to venous return.

    Cardiac Pressures

    • There is variability in cardiac pressures throughout the cycle:
      • Systolic pressure in ventricles and aorta reach approximately 120 mmHg during contraction.
      • Diastolic pressure in the aorta ranges between 70-80 mmHg.

    Heart Sounds

    • Heart sounds are detected via auscultation; produced by valve closures.
    • Audible Sounds:
      • B1: Closure of A-V valves.
      • B2: Closure of sigmoid valves.
    • Non-audible Sounds:
      • B3: Rapid ventricular filling.
      • B4: Atrial contraction.
    • Abnormal heart sounds could indicate valve lesions, such as aortic insufficiency.

    Cardiac Work and Function

    • Cardiac work is the energy used for blood ejection per heartbeat.
    • Defined as: Cardiac Work (W) = Pressure Difference (PD) × Volume Difference (VD).
    • The heart has limited energy reserves, but can efficiently use various substrates, such as fatty acids and lactates.

    Preload and Afterload

    • Preload: Muscle tension at the start of contraction, dependent on LV blood volume at diastole.
    • Afterload: Load the heart must overcome for contraction, correlated with systolic pressure in the aorta.

    Frank-Starling Mechanism

    • Suggests contraction energy relates to the initial length of cardiac muscle fibers.
    • Increased venous return enhances filling and subsequently increases ejection volume (VES).

    Cardiac Output (Qc)

    • Defined as the volume of blood ejected by the ventricle per minute (average 5-6 l/min in adults).
    • Regulated according to body needs, adaptable during physiologic changes:
      • Increases significantly during pregnancy, stress, or physical exercise.

    Measurement of Cardiac Output

    • Fick Principle: Measures oxygen consumption related to arteriovenous oxygen difference and cardiac output.
    • Other methods include:
      • Echo-Doppler: Common but less precise.
      • Thermodilution: Utilizes temperature change for cardiac output estimation.

    Clinical Relevance

    • Low cardiac output can result from conditions like myocardial infarction or hypovolemia.
    • High cardiac output may occur in anemia or reduced afterload conditions.

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    Related Documents

    The Cardiac Cycle 2023.docx.pdf

    Description

    Explore the mechanisms of the cardiac revolution, which includes the phases of systole and diastole. Understand the dynamics of the cardiac cycle as it relates to heart contractions, blood ejection, and the significant differences in duration between systole and diastole. Learn how heart rates affect these phases, especially in trained athletes.

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