Cardiovascular Systerm

Cards (17)

  • Cardiovascular system

    Consists of heart, blood vessels, and blood. Transports oxygen, hormones, nutrients to cells. Removes CO2 and waste from the body. Regulates body temperature via vasodilation and vasoconstriction.
  • Heart chambers

    • Right and left atrium; right and left ventricle
    • Atria act as low-pressure collecting chambers
    • Ventricles act as high-power pumps
    • Interatrial septum separates right and left atria
    • Interventricular septum separates right and left ventricles
    • Prevents oxygen-rich and oxygen-poor blood from mixing
  • Blood flow through the heart
    1. Right atrium: Deoxygenated blood enters from inferior and superior vena cava
    2. Tricuspid valve: Opens due to pressure; right ventricle fills passively. Atrial contraction completes filling
    3. Right ventricle: Contracts, tricuspid valve closes, pulmonary valve opens. Blood enters pulmonary artery
    4. Lungs: Blood oxygenated in capillaries
    5. Left atrium: Oxygenated blood returns via pulmonary veins
    6. Mitral valve: Opens due to pressure; left ventricle fills passively. Atrial contraction completes filling
    7. Left ventricle: Contracts, mitral valve closes, aortic valve opens. Blood enters aorta
    8. Aorta: Oxygenated blood distributed to body
  • Walls of the heart

    • Enclosed in fluid-filled pericardium
    • Epicardium: Outer layer, inner layer of pericardial sac
    • Myocardium: Middle layer, 2/3 of heart muscle
    • Endocardium: Innermost layer, lines chambers and valves
  • Cardiac cycle
    • Two phases: Diastole (relaxation): chambers fill with blood. Systole (contraction): chambers pump blood out
    • Cycle duration: Approx. 0.8 seconds
    • Time split: 2/3 in diastole, 1/3 in systole
  • Internal control of heart rate
    1. Pacemaker sinoatrial (SA) node: located in right atrium
    2. Sets default rate: 60-100 bpm
  • External control of heart rate
    1. Cardiac centre in medulla oblongata receives input from autonomic nervous system
    2. Adjusts heart rate, contraction strength, stroke volume
    3. Baroreceptors: monitor blood pressure
    4. Parasympathetic nervous system: dominant at rest, slows heart rate
    5. Sympathetic nervous system: active during stress/exercise, increases rate
  • Control of stroke volume

    • Preload: stretch of ventricle muscles during diastole
    • Contractility: heart muscle's ability to contract. Influenced by preload
    • Afterload: pressure to overcome aorta resistance
  • The conduction system

    1. SA Node: Initiates impulse
    2. AV Node: Delays impulse 1/10 second
    3. Bundle of His, Left/Right bundle branches: Carry impulse to ventricles
    4. Purkinje Fibres: Trigger ventricular contraction
  • Electrocardiogram (ECG)

    • Records electrical activity
    • P wave: SA node firing, atrial contraction
    • QRS Complex: impulses to Purkinje fibres, ventricular contraction
    • T wave: ventricular relaxation, chamber filling
  • Blood vessels
    • Types: arteries, capillaries, veins
    • Subdivisions: arterioles, venules
  • Layers in blood vessel walls
    • Tunica intima: smooth, frictionless surface
    • Tunica media: smooth muscle, controls vasodilation/vasoconstriction. Influences blood pressure
    • Tunica externa: fibrous tissue, adds support
  • Differences: arteries vs. veins

    Arteries: Thick, strong walls. Carry blood away from the heart. Withstand high pressure.
    Veins: Thinner, less elastic walls. Carry blood toward the heart. House 2/3 of body's blood. One-way valves assist in venous return. Skeletal muscles and respiratory system assist in pumping blood back.
  • Capillaries

    • Smallest blood vessels, 0.0025-0.25 cm. Red blood cells pass in single file.
    Function: Site for O2 and CO2 gas exchange. Pores in kidneys, liver, etc., allow passage of hormones, white blood cells.
    Blood flow control: Precapillary sphincter controls blood flow. Reacts to local chemical conditions like pH, O2, CO2, temperature.
    During exercise: Blood flow to muscles increases from 15% to 85%.
    Capillary beds: Interconnected network. Merge with venules, then larger veins, leading back to the heart.
  • Pulmonary circulation
    Entry: deoxygenated blood enters right atrium via inferior/superior venae cavae.
    Right atrium to right ventricle: through tricuspid valve.
    Pulmonary valve: right ventricle contracts, blood goes to pulmonary artery.
    Pulmonary artery: splits into smaller arteries to lungs.
    Arterioles and capillaries: merge in lungs.
    Oxygenation: blood oxygenated in lungs, moves to venules.
    To heart: via four pulmonary veins to left atrium.
  • Systemic circulatory system
    Closed-loop network: arteries, arterioles, capillaries, venules, veins.
    Functions: Transports oxygen, hormones, water, and nutrients to tissues; returns waste and CO2 to the heart.
    Start of systemic circulation: Left ventricle pumps blood to aorta. Ascending aorta rises and arches left, becoming descending aorta in thorax and abdomen.
    Major arterial branches: Right and left coronary arteries from ascending aorta -> heart. Brachiocephalic, left common carotid, left subclavian from aortic arch -> head, neck, arms. Descending aorta branches -> organs like liver, spleen, kidneys.
    Microcirculation and return: Arteries -> arterioles -> capillaries for exchange. Blood drains into venules, merges into veins.
    End of systemic circulation: Lower veins -> inferior vena cava. Upper veins -> superior vena cava. Both drain into right atrium.
  • Cardiac circulation

    Oxygen supply to the heart: Heart's oxygen not supplied by blood in its chambers. Right and left coronary arteries supply oxygen-rich blood.
    Origin and timing: Coronary arteries arise from base of aorta. Fill when ventricles are relaxed; closed during ventricular contraction.
    Drainage: Blood from coronary arteries -> cardiac veins. Drains into coronary sinus on posterior wall of right atrium.