Heart’s Blood Supply and Circulation
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Questions and Answers

What is the primary function of the coronary circulation in the heart?

  • Supply deoxygenated blood to the heart
  • Supply deoxygenated blood to the brain
  • Supply oxygenated blood to the heart muscle (correct)
  • Supply oxygenated blood to the lungs

    • Which artery carries the greatest blood volume in the heart's coronary circulation?

  • Left coronary artery (correct)
  • Right coronary artery
  • Carotid artery
  • Pulmonary artery

    • Where does the blood leave the tissues of the left ventricle and right ventricle?

  • Coronary sinus and anterior cardiac veins (correct)
  • Pulmonary artery
  • Renal artery
  • Aorta

    • What percentage of oxygen does the myocardium extract from blood in coronary vessels at rest?

    <p>70-80%</p> Signup and view all the answers

    How does coronary blood flow increase to provide more oxygen supply to the myocardium during exercise?

    <p>By dilating coronary vessels</p> Signup and view all the answers

    Why does the myocardium depend on adequate oxygen supply?

    <p>It has limited anaerobic capacity</p> Signup and view all the answers

    What is the significance of a blood clot in a coronary vessel?

    <p>Impairs normal heart function</p> Signup and view all the answers

    What is the formula for Rate-Pressure Product (RPP)?

    <p>RPP = SBP x HR</p> Signup and view all the answers

    What fuels are primarily used by the myocardium during rest?

    <p>Fat/lipids</p> Signup and view all the answers

    What is the purpose of using exercise to evaluate myocardial blood flow?

    <p>To determine if blood flow meets myocardial demands</p> Signup and view all the answers

    How does intense exercise affect myocardial metabolism?

    <p>Shifts to glucose and lactate utilization</p> Signup and view all the answers

    What is the role of the Sinoatrial (SA) node in cardiac muscle?

    <p>Generating the electrical impulse that initiates the heart's contraction</p> Signup and view all the answers

    How does an Electrocardiogram (ECG) monitor heart rate during physical activity?

    <p>By recording the heart's electrical activity during a cardiac cycle</p> Signup and view all the answers

    What happens when an impulse originates from the sinoatrial (SA) node in the right atrium?

    <p>The right atrium contracts first</p> Signup and view all the answers

    Why does cardiac muscle maintain its own rhythm?

    <p>To ensure continuous blood circulation</p> Signup and view all the answers

    How does an ECG lead create a composite electrical '3D picture' of myocardial activity?

    <p>By visualizing the electrical field created by myocardium's activity</p> Signup and view all the answers

    What is the primary function of repeating electrical impulses traveling through the heart in cardiac conduction?

    <p>To control muscle contraction and dilation of the heart</p> Signup and view all the answers

    What is the function of the atrioventricular bundle in the heart's electrical conduction system?

    <p>To facilitate the spread of impulses into the ventricles</p> Signup and view all the answers

    What does the QRS complex in an ECG represent?

    <p>Ventricular depolarization before ventricular contraction</p> Signup and view all the answers

    How would a large low space in the heart affect its function based on the text?

    <p>Result in the heart not being told to contract, leading to potential issues</p> Signup and view all the answers

    Which phase of the normal ECG represents ventricular repolarization?

    <p>T-wave</p> Signup and view all the answers

    What is a key indicator of allowing the cardiac system to relax and recover, based on HRV information provided in the text?

    <p>Regular R to R intervals</p> Signup and view all the answers

    How does the Sinoatrial node (SA) contribute to cardiac functioning?

    <p>Initiates impulse that starts each heartbeat</p> Signup and view all the answers

    What is the main function of the Sinoatrial (SA) node in the heart?

    <p>Creating electrical impulses to control heart muscle contraction</p> Signup and view all the answers

    How does an Electrocardiogram (ECG) represent the heart's electrical activity?

    <p>By creating a composite record of electrical events during a cardiac cycle</p> Signup and view all the answers

    What causes a slight asynchrony in the contraction of the right and left sides of the heart?

    <p>Nerve impulse transmission timing</p> Signup and view all the answers

    What is the role of the ECG leads in creating an electrical '3D picture' of myocardial activity?

    <p>Transmitting electrical signals to a recorder</p> Signup and view all the answers

    Where does the impulse originating from the Sinoatrial (SA) node travel first in the heart?

    <p>Across the atria causing them to contract</p> Signup and view all the answers

    What characterizes a valid ECG tracing according to the text?

    <p>'3D picture' creation and proper electrode placement</p> Signup and view all the answers

    What is the purpose of the P wave in an ECG?

    <p>Depolarization of atria before atria contract</p> Signup and view all the answers

    Which structure allows the impulse to pass from the atria to the ventricles in the heart?

    <p>Atrioventricular bundle (bundle of His)</p> Signup and view all the answers

    What is the primary role of Purkinje's fibers in the heart's electrical conduction system?

    <p>Facilitate ventricular depolarization</p> Signup and view all the answers

    During which phase of a normal ECG does ventricular diastole occur?

    <p>T-wave</p> Signup and view all the answers

    How does a heart block, as mentioned in the text, impact cardiac functioning?

    <p>Causes large low spaces that prevent contraction signals</p> Signup and view all the answers

    What does a greater Heart Rate Variability (HRV) indicate about the cardiac system's condition?

    <p>Improved ability to relax and recover</p> Signup and view all the answers

    What is the role of the Sinoatrial (SA) node in cardiac muscle?

    <p>It provides the inherent stimulus for heart action.</p> Signup and view all the answers

    What happens when an impulse originates from the Sinoatrial (SA) node in the right atrium?

    <p>It causes the atria to contract.</p> Signup and view all the answers

    How does the myocardium's electrical activity affect an Electrocardiogram (ECG)?

    <p>Forms an electrical field throughout the body.</p> Signup and view all the answers

    What characteristic makes the Sinoatrial (SA) node stand out in terms of heart function?

    <p>It maintains the heart's intrinsic rhythmicity.</p> Signup and view all the answers

    Why is proper electrode placement essential for obtaining a valid ECG tracing?

    <p>To ensure accurate transmission of electrical signals.</p> Signup and view all the answers

    How does myocardial impulse transmission differ from regular tissue impulse transmission?

    <p>It repeats to control rhythmic contraction and dilation of heart muscle.</p> Signup and view all the answers

    What is the main role of the Atrioventricular bundle (bundle of His) in the heart's electrical conduction system?

    <p>Facilitating the contraction of the ventricles</p> Signup and view all the answers

    During which phase of a Normal ECG does the QRS complex occur?

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

    What is the primary function of Purkinje's fibers in the heart?

    <p>Facilitating rapid transmission of impulses for coordinated ventricular contraction</p> Signup and view all the answers

    What happens during atrial repolarization in an ECG?

    <p>It makes the T wave smaller</p> Signup and view all the answers

    How does Heart Rate Variability (HRV) typically indicate the condition of the cardiac system?

    <p>Greater HRV suggests better ability to relax and recover</p> Signup and view all the answers

    What does a large low space in the heart suggest based on the text?

    <p>Potential issues with heart contraction signaling</p> Signup and view all the answers

    Study Notes

    Heart's Blood Supply

    • The heart has its own circulatory network, the coronary circulation, which arises from the heart's top portion.
    • The right and left coronary arteries supply blood to the heart muscle.
    • The left coronary artery has the greatest blood volume flow, feeding the left atrium and left ventricle, and the right ventricle.
    • Blood leaves the tissues of the left ventricle through the coronary sinus and the right ventricle through the anterior cardiac veins, both dumping into the right atrium.
    • Normal blood flow to the myocardium at rest is 200-250 ml/min (5% of total output).

    Myocardial Oxygen Supply and Use

    • At rest, the myocardium extracts 70-80% of oxygen from the blood in coronary vessels.
    • Proportionate increase in coronary blood flow during exercise provides the sole mechanism to increase myocardial oxygen supply.
    • Two factors increase myocardial blood flow:
      • Increase in metabolism dilates coronary vessels.
      • Increase in aortic pressure during exercise forces a proportionately greater volume of blood into the coronary circulation.

    Impaired Myocardial Blood Supply

    • The myocardium depends on adequate oxygen supply because it has limited anaerobic capacity and can't make an extensive switch.
    • Extensive vascular perfusion supplies at least one capillary to each of the heart's muscle fibers.
    • Tissue hypoxia provides a potent stimulus to myocardial blood flow, which can produce chest pains (angina pectoris).
    • A blood clot in a coronary vessel can impair normal heart function, leading to a myocardial infarction, where heart tissue will die due to lack of oxygen.

    Rate-Pressure Product (RPP)

    • RPP is an estimate of myocardial workload and VO2.
    • RPP is computed from the product of peak SBP measured at the brachial artery and heart rate.
    • RPP is an index of relative cardiac work and relates closely to directly measured myocardial VO2 and coronary blood flow in healthy subjects over a wide range of exercise intensities.
    • RPP ranges from 6000 at rest to greater/equal to 40,000 during exercise, depending on intensity and mode.

    Myocardial Metabolism

    • At rest, the heart muscle uses fat/lipids as fuel.
    • During moderate exercise, glucose and lactate are used more.
    • During intense exercise, lactate is oxidized.

    Intrinsic Regulation of Heart Rate

    • Unlike other tissues, cardiac muscle maintains its own rhythm.
    • Left to its inherent rhythmicity, the heart would beat around 100 bpm.
    • The sinoatrial (SA) node provides the innate stimulus for heart action and is the "heart's pacemaker".

    Normal Route of Myocardial Impulse Transmission

    • The sinoatrial node (SA) in the right atrium is the origin of the impulse.
    • The impulse spreads across the atria, causing them to contract.
    • The impulse passes to the atrioventricular node (AV), travels along the atrioventricular bundle into its two branches (right and left crus), and spreads into the ventricles, causing them to contract.
    • Dissipation of the impulse causes the atria and ventricles to relax or dilate.

    Electrocardiogram (ECG)

    • The myocardium's electrical activity creates an electrical field throughout the body.
    • ECG represents a composite record of the heart's electrical events during a cardiac cycle.
    • These electrical events can monitor HR during physical activity and exercise stress testing.
    • A valid ECG tracing requires proper electrode placement.
    • ECG leads transmit the electrical signal to a recorder, which creates a composite electrical "3D picture" of myocardial activity.

    ECG Waves

    • P wave: depolarization of atria before atria contract.
    • QRS complex: signals electrical changes from ventricular depolarization before ventricles contract.
    • Atrial repolarization after P wave, but it's obscured by the QRS complex.
    • T-wave: represents ventricular repolarization that occurs during ventricular diastole.

    Electrocardiogram (ECG) and Heart Rate

    • Typically, R to R measurement is used to measure HR, which is typically irregular, indicating decent recovery.
    • Greater HRV (heart rate variability) is a better indication of allowing the system to relax and recover.

    Electrocardiogram (ECG) and Pathology Detection

    • Large low spaces on the ECG can indicate that the heart is not told to contract, which can be an issue (e.g., heart block).

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    Description

    Explore the coronary circulation network providing blood supply to the heart, including the right and left coronary arteries. Learn about the distribution of blood to different parts of the heart and the role of coronary sinus and cardiac veins in returning blood to the right atrium.

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