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Cardiovascular System and Heart Physiology - Anatomy & Physiology

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  • Functions of the cardiovascular system

    The cardiovascular system transports nutrients, gases, and wastes; regulates body temperature and pH; and protects against blood loss and infection.

  • Organization of the cardiovascular system starting and ending in the aorta

    Blood flows from the aorta to arteries, arterioles, capillaries, venules, veins, and returns to the heart via the venae cavae, completing the circuit back to the aorta.

  • Relationship between pressure and flow in the cardiovascular system

    Blood flows from areas of higher pressure to lower pressure; flow rate depends on pressure gradients, resistance, and vessel radius.

  • Definition of hydrostatic pressure in blood vessels

    Hydrostatic pressure is the force exerted by blood against vessel walls, driving fluid out of capillaries.

  • How vessel radius affects resistance and flow

    Resistance is inversely proportional to the fourth power of the radius; small changes in radius greatly affect flow and resistance.

  • Internal anatomy of the heart

    The heart has four chambers: two atria and two ventricles, separated by valves that ensure unidirectional blood flow.

  • External anatomy of the heart

    The heart is enclosed by the pericardium and has major vessels including the aorta, pulmonary arteries, and veins attached externally.

  • Two types of myocardial cells

    Autorhythmic cells generate electrical impulses; contractile cells produce force for heart contractions.

  • Arrangement of myocardial cells in the heart

    Myocardial cells are arranged in layers with contractile cells forming the bulk of the myocardium and autorhythmic cells forming the conduction system.

  • Membrane proteins involved in myocardial excitation-contraction coupling

    Voltage-gated sodium, calcium, and potassium channels regulate ion movement triggering contraction and relaxation in myocardial cells.

  • Ion movement during myocardial excitation-contraction coupling

    Depolarization opens sodium channels; calcium influx triggers contraction; potassium efflux repolarizes the cell for relaxation.

  • Action potentials of autorhythmic vs contractile myocardial cells

    Autorhythmic cells have spontaneous depolarization; contractile cells have a stable resting potential and longer action potentials.

  • Conduction pathway of electrical signals in the heart

    Signals start at the sinoatrial node, pass to the atrioventricular node, then through the bundle of His, bundle branches, and Purkinje fibers.

  • Parts of an electrocardiogram (ECG)

    The ECG includes the P wave (atrial depolarization), QRS complex (ventricular depolarization), and T wave (ventricular repolarization).

  • Relationship between ECG electrical events and cardiac mechanical events

    Electrical depolarization triggers atrial and ventricular contraction; repolarization corresponds to relaxation phases.

  • Pressure changes during the cardiac cycle

    Pressure rises during ventricular systole to eject blood and falls during diastole to allow filling.

  • Relationship between heart rate, cardiac output, and stroke volume

    Cardiac output = heart rate × stroke volume; it measures blood volume pumped per minute.

  • Role of autonomic nervous system in heart rate control

    Sympathetic stimulation increases heart rate and contractility; parasympathetic stimulation decreases heart rate.

  • Factors influencing stroke volume

    Stroke volume is affected by venous return, preload, afterload, contractility, skeletal muscle pump, respiratory pump, and inotropic agents.

  • Length-Tension

    Stretching heart muscles optimizes overlap of actin and myosin, producing stronger contraction and larger stroke volume

  • Afterload

    Resistance or blood pressure in arteries and ventricles push to eject blood; increase in it decreases stroke volume

  • Contractility

    Mechanical strength of heart contraction is independent on preload or afterload increase causes increase in stroke volume

  • Inotropic Agents

    Chemical substances/drugs (epinephrine) after contractility; positive increases stroke volume, negative decreases

  • Venous Return

    Increase causes increase in filling ventricles, raising end diastole volume and increasing preload

  • Preload

    Degree of strength on ventricles at the end of diastole increasing causes increases in stroke volume

  • Skeletal Muscle Pump

    Contracting leg and body squeeze veins, pushing blood towards heart and increasing venous and stroke volume

  • Respiratory Pump

    Breathing changes pressure in chest; inhalation lowers pressing, pulling blood towards the heart and enhancing venous