Cardiovascular System: The Heart
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Questions and Answers

What role does the right atrium play in the cardiovascular system?

  • It pumps oxygenated blood to the body.
  • It houses the bicuspid valve.
  • It connects directly to the pulmonary trunk.
  • It receives deoxygenated blood from three sources. (correct)

    • What is the primary role of the delay at the AV node?

  • To enable atria to fully contract and fill ventricles (correct)
  • To allow ventricles to contract before atria
  • To prevent any electrical signal from reaching the ventricles
  • To shorten the duration of the cardiac cycle

    • What is the function of the pulmonary semilunar valve?

  • It prevents backflow of blood into the left atrium.
  • It opens to allow deoxygenated blood to enter the left ventricle.
  • It controls blood flow from the left ventricle to the aorta.
  • It allows blood to flow from the right ventricle into the pulmonary trunk. (correct)

    • What characterizes the refractory period in cardiac muscle?

    <p>A second contraction cannot be triggered during this time.</p> Signup and view all the answers

    Which chambers of the heart are primarily involved in systemic circulation?

    <p>Left atrium and left ventricle</p> Signup and view all the answers

    Which part of the electrocardiogram represents atrial depolarization?

    <p>P wave</p> Signup and view all the answers

    Which component of heart cells is responsible for generating spontaneous action potentials?

    <p>Autorhythmic cells</p> Signup and view all the answers

    What is the approximate stroke volume of each ventricle per beat?

    <p>70 ml</p> Signup and view all the answers

    Which structure initiates the heartbeat in the conduction system of the heart?

    <p>SA node</p> Signup and view all the answers

    What defines the end diastolic volume (EDV)?

    <p>Volume of blood in the ventricles at the end of diastole</p> Signup and view all the answers

    What is the primary function of the left ventricle?

    <p>Pumps oxygenated blood into the aorta.</p> Signup and view all the answers

    How does the autonomic nervous system influence heart rate?

    <p>It modifies both the rate and strength of contractions.</p> Signup and view all the answers

    Why does the left ventricle push blood with more force than the right ventricle?

    <p>It has a thicker wall compared to the right ventricle.</p> Signup and view all the answers

    How long does one complete cardiac cycle typically take?

    <p>0.8 sec</p> Signup and view all the answers

    What type of blood does the right ventricle pump?

    <p>Deoxygenated blood to the lungs.</p> Signup and view all the answers

    How much blood pressure is typically found in the pulmonary trunk?

    <p>30 mm Hg</p> Signup and view all the answers

    What is the formula for calculating cardiac output?

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

    How does increased preload affect stroke volume according to the Frank-Starling law?

    <p>It increases stroke volume.</p> Signup and view all the answers

    Which factor directly affects myocardial contractility?

    <p>Inotropic agents</p> Signup and view all the answers

    What does an increase in ejection fraction (EF) indicate?

    <p>Increased contractility</p> Signup and view all the answers

    What is the primary body mechanism for short-term control of cardiac output?

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

    Which statement about afterload is correct?

    <p>Afterload is the pressure that must be overcome for semilunar valves to open.</p> Signup and view all the answers

    In congestive heart failure, what effect does increased preload have on the heart?

    <p>It decreases the heart's efficiency.</p> Signup and view all the answers

    Which of the following hormones plays a role in heart rate regulation?

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

    Study Notes

    Cardiovascular System: The Heart

    • The heart's muscle cells are branched and have a single nucleus, connected by intercalated disks
    • Myocardial muscle cells are specialized for efficient pumping action
    • The heart has four chambers: right atrium, right ventricle, left atrium, and left ventricle
    • The right atrium receives deoxygenated blood from three sources (superior vena cava, inferior vena cava, and coronary sinus)
    • From the right atrium, blood flows through the tricuspid valve into the right ventricle
    • The right ventricle pumps blood through the pulmonary semilunar valve into the pulmonary trunk
    • The left atrium receives oxygenated blood from the lungs (four pulmonary veins)
    • From the left atrium, blood flows through the bicuspid (mitral) valve into the left ventricle
    • The left ventricle pumps blood through the aortic semilunar valve into the aorta
    • Blood flows through the heart in a specific path, ensuring that deoxygenated and oxygenated blood do not mix

    Cardiac Muscle Histology

    • Cardiac muscle cells are branched and have a single nucleus
    • These cells are connected to each other by specialized junctions called intercalated disks
    • The intercalated disks enable rapid transmission of electrical signals throughout the heart

    Blood Circulation

    • Pulmonary circulation: The right side of the heart pumps deoxygenated blood to the lungs for gas exchange, returning oxygenated blood to the left side of the heart
    • Systemic circulation: The left side of the heart pumps oxygenated blood to the body's tissues, returning deoxygenated blood to the right side of the heart

    Heart Cells

    • Cardiac muscle is composed of two types of cells: autorhythmic cells (10%) and contractile cells (90%)
    • Autorhythmic cells are self-excitable and generate spontaneous action potentials (pacemaker potentials), initiating and regulating the heartbeat
    • Contractile cells respond to these signals and contract to pump blood

    Conduction System of the Heart

    • The SA node (sinoatrial node) is the heart's pacemaker, firing spontaneously at 90-100 times per minute
    • Signals from the SA node spread through the atria, causing them to contract
    • The AV node (atrioventricular node) delays the signal to allow the atria to fully contract before the ventricles contract
    • Impulses move through the AV bundle (bundle of His) and its branches into Purkinje fibers in the ventricles, triggering ventricular contraction

    Action Potential in Cardiac Muscle

    • Cardiac muscle action potentials have a unique plateau phase due to calcium ion influx maintaining depolarization.
    • This plateau prolongs the refractory period, preventing tetanus and ensuring proper cardiac function

    Physiology of Contraction

    • The refractory period in cardiac muscle ensures that the heart can properly fill between contractions, preventing tetanus (sustained contraction)

    Electrocardiogram (ECG)

    • An ECG measures electrical activity spread through the heart
    • Waves on an ECG correspond to electrical events in the heart (e.g., atrial depolarization, ventricular depolarization, ventricular repolarization)
    • The ECG allows for diagnosis of various cardiac abnormalities

    P wave

    • Represents atrial depolarization, causing atrial contraction

    QRS complex

    • Represents ventricular depolarization, causing ventricular contraction

    T wave

    • Represents ventricular repolarization

    Cardiac Cycle

    • The cardiac cycle is a complete sequence of contraction and relaxation of the heart
    • One cycle typically takes around 0.8 seconds
    • Key aspects of the cycle include end-diastolic volume (EDV), end-systolic volume (ESV), and stroke volume (SV)

    Ventricular Pressures

    • The pressure in the aorta is 120 mmHg during systole
    • The pressure in the pulmonary trunk is lower, around 30 mmHg
    • Ventricular wall thickness allows the left ventricle to exert more force for systemic circulation

    Cardiac Output

    • Cardiac output (CO) is the volume of blood pumped per minute from the left ventricle into the aorta
    • CO is calculated as heart rate (HR) multiplied by stroke volume (SV)

    Influences on Stroke Volume

    • Stroke volume can be affected by preload, contractility, and afterload
    • Preload is determined by ventricular end-diastolic volume (EDV)
    • Contractility is the heart's ability to contract more forcefully at a given preload. Influenced by inotropic agents
    • Afterload is the pressure the heart must overcome to pump blood into the arteries

    Starling's Law

    • Starling's Law states that increasing preload increases stroke volume (stretch leads to more forceful contraction)

    Influences on Heart Rate

    • Heart rate is regulated by the autonomic nervous system (sympathetic and parasympathetic)

    Epinephrine (and norepinephrine)

    • Increase contractility and heart rate
    • Increase the duration of calcium channels opening

    Afterload

    • Afterload is the pressure exerted by the blood in the aorta against the closing of the semilunar (aortic) valves
    • High afterload can reduce stroke volume

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    Cardiovascular System: The Heart PDF

    Description

    Explore the structure and function of the heart with this quiz. Understand the unique characteristics of myocardial muscle cells and the flow of blood through the heart's four chambers. Test your knowledge on how deoxygenated and oxygenated blood are managed within this essential organ.

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