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Cardiovascular System: Cardiac Function - Anatomy & Physiology

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  • Major components of the cardiovascular system

    Heart, blood vessels, and blood transport oxygen, nutrients, wastes, hormones, immune cells, and clotting proteins throughout the body.

  • Path of blood flow through the heart and vasculature

    Left ventricle → aorta → systemic circuit → vena cavae → right atrium → right ventricle → pulmonary artery → pulmonary circuit → pulmonary veins → left atrium → left ventricle.

  • Types of blood vessels and their functions

    Arteries carry blood away from the heart; arterioles have high resistance; capillaries are sites of exchange; venules and veins return blood to the heart.

  • Components of blood

    Erythrocytes transport oxygen and CO2; leukocytes defend against pathogens; platelets aid clotting; plasma is the fluid and solute medium.

  • Coronary circulation

    Heart's own capillaries supplied by coronary arteries arising from the aorta, providing nutrients to cardiac muscle cells.

  • Layers of the heart wall

    Epicardium (outer membrane), myocardium (cardiac muscle), and endocardium (inner endothelial layer).

  • Function of heart valves

    Valves ensure unidirectional blood flow by opening and closing passively based on pressure gradients, preventing backflow.

  • Types of heart valves

    Atrioventricular (AV) valves: tricuspid (right) and bicuspid/mitral (left); Semilunar valves: aortic and pulmonary valves.

  • Role of papillary muscles and chordae tendineae

    Prevent AV valves from everting by anchoring valve cusps during ventricular contraction.

  • Autorhythmicity in the heart

    Ability of pacemaker cells to generate spontaneous action potentials, coordinating heartbeat rhythm.

  • Main pacemaker of the heart

    Sinoatrial (SA) node initiates action potentials at 70–80 AP/min, setting the heart rate.

  • Conduction system pathway

    SA node → atrial muscle → AV node (delay) → bundle of His → left and right bundle branches → Purkinje fibers → ventricular muscle contraction.

  • Intercalated disks in cardiac muscle

    Contain desmosomes for mechanical strength and gap junctions for electrical coupling between cardiac cells.

  • Phases of pacemaker cell action potential

    1. Spontaneous depolarization (Na+ funny channels open)
    2. Threshold reached (Ca2+ channels open)
    3. Repolarization (K+ channels open)

  • Phases of cardiac contractile cell action potential

    Phase 0: Na+ influx
    Phase 1: Na+ channels close
    Phase 2: Ca2+ influx, K+ efflux
    Phase 3: K+ efflux
    Phase 4: resting potential

  • Excitation-contraction coupling in cardiac muscle

    AP triggers Ca2+ entry via T tubules and sarcoplasmic reticulum, Ca2+ binds troponin, enabling crossbridge cycling and contraction.

  • Electrocardiogram (ECG) waves and their meaning

    P wave: atrial depolarization
    QRS complex: ventricular depolarization and atrial repolarization
    T wave: ventricular repolarization

  • Phases of the cardiac cycle

    1. Ventricular filling
    2. Isovolumetric contraction
    3. Ventricular ejection
    4. Isovolumetric relaxation

  • Heart sounds and their causes

    First sound (lubb): AV valves closing
    Second sound (dupp): Semilunar valves closing

  • Cardiac output formula

    Cardiac output (CO) = Stroke volume (SV) × Heart rate (HR)

  • Factors affecting heart rate

    Autonomic nervous system: parasympathetic lowers HR, sympathetic raises HR; hormones like epinephrine increase HR.

  • Factors affecting stroke volume

    Ventricular contractility, end-diastolic volume (preload), and afterload influence stroke volume.

  • Starling's law of the heart

    Increased end-diastolic volume stretches cardiac muscle fibers, leading to stronger contraction and increased stroke volume.

  • Sympathetic control of ventricular contractility

    Norepinephrine binds β1 receptors, increasing Ca2+ channel opening and enhancing contraction strength.