Mapa mental

Cardiovascular system

Gillian C Inglês

Mind map: Cardiovascular system

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heart
- 4 chambers
  - right atrium
    - receives blood from systemic circuit
  - right ventricle
    - pumps blood into pulmonary circuit
  - left atrium
    - receives blood from pulmonary circuit
  - left ventricle
    - pumps blood into systemic circuit
- base
  - superior
  - where great vessels connect
- apex
  - inferior
  - pointed tip
- sits between 2 pleural cavities in mediastinum
  - mediastinum: space between both lungs inside the chest cavity
- valves
  - atrioventricular
    - tricuspid
    - mitral
    - folds of fibrous tissue that extends into opening between atria and ventricles
    - permit blood flow in one direction: atrium->ventricle
  - semilunar
    - pulmonary
    - aortic
    - prevents backflow of blood into ventricles
- conducting system
  - heartbeat
    - a single cardiac contraction
    - cardiac cycle
      - from start of one heartbeat to beginning of next
        including alternating periods of contraction and relaxation
      - phases within chambers
        systole
        1.atrial
        1)atrial contraction begins
        2)right and left AV valves open
        3)atria eject blood into ventricles
        4)ends
        2.ventricular
        4)ventricle contracts and builds pressure
        5)AV valves close
        producing isovolumetric contraction
        ventricular pressure exceeds arterial pressure
        6)opens semilunar valves
        7)ventricular ejection
        amount of blood ejected = stroke volume (SV)
        ventricular pressure falls, ventricles contain end-systolic volume (ESV) (40% of end-diastolic volume)
        8)Seminlunar valves close
        blood pressure rises
        diastole
        2.atrial
        4)begins
        ventricles contain maximum blood volume (EDV)
        3.ventricular
        isovlumetric relaxation
        all heart valves are closed
        ventricular pressure is higher than atrial pressure
        blood cannot flow into ventricles
        9)AV valves open
        ventricles fill passively
        atrial pressure is higher than ventricular pressure
        blood pressure falls
      - 75 heart beats per minute (bpm)
      - a cycle lasts 800 ms
      - blood flows from an area of higher pressure to one of lower pressure
        controlled by timing of contractions and directed by one-way valves
      - when heart rate increases all phases of cycle shorten, particularly diastole
  - cardiac muscle cells
    - autorhythmic
      - control and coordinate heartbeat
    - contractile
      - produce contraction that propel blood (99%)
        role of calcium ions
        extracellular Ca2+ crosses plasma membrane during plateau phase
        provides 20% of Ca2+ required for contraction
        entr
        entry of extracellular Ca2+ from sarcoplasmic reticulum
        SR is a specialized type of smooth ER that regulates the calcium ion conc. in the cytoplasm of muscle cells
        cardiac muscle tissues are very sensitive to extracellular Ca2+ conc.
        as slow calcium channels close, intracellular Ca2+ is pumped back into SR or out of cell
      - form bulk of atrial and ventricular walls
      - receive stimulus from Pukinje fibres
      - resting membrane potential
        ventricular cell
        -90mV
        atrial cell
        -80mV
      - action potential
        1.rapid depolatization
        massive influx of Na+ through fast sodium channels
        2.plateau
        extracellular Ca2+ enters cytosol through slow calcium channel
        3.repolarization
        K+ rushes out of cells through slow potassium channels
        refractory
        absolute (200ms)
        cardiac contractile cells cannot respond
        relative (50ms)
        cells respond only to strong stimuli
  - pacemaker cells
    - establishes normal cardiac rhythm
    - found in
      - Sinoatrial (SA) node
        in wall of right atrium
      - atrioventricular (AV) node
        at junction between atria and ventricles
    - potential
      - gradual depolarization
        do not have a stable resting membrane potential
      - rate of spontaneous depolarization
        SA node faster than AV node
      - SA node depolarizes first
        establishing sinus rhythm
      - parasympathetic stimulation slows heart rate
  - conducting cells
    - found in
      - internodal pathways of atria
      - atrioventricular bundle, bundle branches, Purkinje fibres of ventricles
  - impulse conduction
    - 1.SA node activity and atrial activation begins
      - 2.stimulus spreads across atria and reaches AV node
        3.impulse is delayed for 100ms at AV node
        atrial contraction begins
        4.impulse travels in AV bundle to left and right bundle branches in interventricular septum
        to Purkinje fibres and to papillary muscles via moderator band
        5.Purkinje fibres distribute impulse to ventricular myocardium
        atrial contraction is completed; ventricular contraction begins
  - electrocardiogram (ECG)
    - a recording of electrical events in the heart
      - obtained by placing electrodes at specific locations on body surface
    - abnormal patterns are used to diagnose damage
    - P wave
      - depolarization of atria
    - QRS complex
      - depolarization of ventricles; ventricles begin contracting shortly after P wave
    - T wave
      - repolarization of ventricles
    - P-R interval
      - from start to atrial depolarization; to start of QRS complex
    - Q-T interval
      - time required for ventricles to undergo a single cycle of depolarization and repolarization
  - intercalated discs
    - unique structural formations found between the myocardial cells of the heart
    - bond cardiac muscle cells together
    - membranes of adjacent cells are held together by desmosomes; linked by gap junctions
    - transfer force of contraction from cell to cell
    - propagate action potentials
- heart sounds
  - detected withh a stethoscope
  - S1
    - loud sounds as AV valves are closed
  - S2
    - loud sounds as semilunar valves close
  - S3, S4
    - soft sounds - blood flowing into ventricles and atrial contraction
blood
- flow
  - 1.superior and inferior vena cava
    - 2.right atrium
      - 3.right ventricle
        4.left pulmonary arteries
        5.pulmonary circuit (lungs)
        gas exchange occurs in the pulmonary capillaries: oxygen into blood, carbon dioxide out)
        6.left pulmonary veins
        7.left atrium
        8.left ventricle
        9.aorta
        10.systemic circuit
        exchange in systemic capillaries: oxygen and nutrients out, carbon dioxide and wastes in
        back to 1. = cycle is repeated
        blood high in oxygen and low in carbon dioxide
        blood is low in oxygen but relatively high in carbon dioxide
- specialized connective tissue
  - contain cell suspended in a fluid matrix
- function
  - 1.transporting dissolved gases, nutrients, hormones and metabolic water
  - 2.regulating pH, ion composition of interstitial fluids
  - 3.restricting fluid losses at injury sites
  - 4.defending against toxins and pathogens
  - 5.stabilizing body temperature
- components
  - whole blood
    - plasma
      - fluid
      - 55% of blood volume
      - >90% is water
        rest contains dissolved plasma proteins and other solutes
    - similar in composition to interstitial fluids because water, ions and small solutes are exchanged across capillary walls
  - fractionation
    - process of separating whole blood into plasma and formed elements
      - plasma proteins
        10% of plasma
        Albumins (60%)
        plasma osmolarity
        transport insolubles (fatty acids, thyroid hormones, steroid hormones)
        Globulins (35%)
        immunoglobulins
        antibodies
        transport globulins
        hormone-binding proteins, metalloproteins, apoliopoproteins (lipoproteins), steroid-binding proteins
        Fibrinogen (4%)
        soluble protein that functions in clotting
        converted to insoluble fibrin during injury
        leave serum (fluid) in blood sample
        Other (1%)
        varying concentrations of enzymes and hormones
      - haemopoiesis
        process of producing formed elements
      - formed elements
        red blood cells (erythrocytes
        haemoglobin (Hb) (280 billion)
        red pigment that gives blood its color (iron)
        protein that transports respiratory gases
        12-18 g/dL whole blood
        complex quaternary structure
        4 globular protein subunits
        2 alpha chains
        2 beta chains
        each with 1 molecule of haem
        each haem contains 1 iron ion
        iron interacts with oxygen to form oxyhaemoglobin, HbO2
        dissociate easily to form deoxyhaemoglobin
        in peripheral capillaries (low O2)
        releases O2
        binds CO2
        carbaminohhaemoglobin
        at lungs (high O2)
        binds O2
        releases CO2
        99.9% of formed elements
        4.2-6.3 million per mcL of whole blood
        small, highly specialized cells
        large SA:V
        quickly absorb and release oxygen
        biconcave discs
        thin central region and thicker outer margin
        form stacks called rouleaux
        smooth blood flow through narrow blood vessels
        binds and transports oxygen and carbon dioxide
        bend and flex when entering small capillaries
        mature RBCs - anucleate
        lack nuclei, mitochondria, ribosomes
        unable to divide, synthesize proteins or repair damage
        live 120 days
        white blood cells (leukocytes)
        have nuclei and other organelles
        lack Hb
        functions
        defending body against pathogens
        removing toxins and waste
        attacking abnormal or damaged cells
        most are in connective tissue proper and organs of lymphatic system
        constitute small fraction of whole blood - 5000-10000 per mcL
        all
        can migrate out of the bloodstream
        are capable of amoeboid movement
        are attracted to specific chemical stimuli (positive chemotaxis)
        some are phagocytic
        platelets (thrombocytes)
        cell fragments
        involved in clotting system
        circulate for 9-12 days
        removed by phagocytes
        mainly (1/3) in spleen (vascular organs)
        150,000-500,000 per mcL of blood
        mobilized in circulatory crisis
        functions
        release important clotting chemical
        temporarily patch damaged vessel walls
        reduce size of break in vessel wall
- Haemostasis/ BLOOD CLOTTING/ cessation of bleeding
  - phases
    - 1.vascular
      - 1.a cut triggers vascular spasm: contraction of smooth muscle fibres of vessel wall (lasts about 30 mins)
        2.endothelial cells contract and expose basement membrane to bloodstream
        3.endothelial cells release chemical factors and local hormones (ADP, tissue factor and prostacyclin; endothelin (peptide hormones))
        4.cause smooth muscle contraction and cell division
        5.endothelia plasma membranes become 'sticky', seal off tear and prevent blood flow
    - 2.platelet
      - platelet adhesion
        1.platelets attach to exposed surfaces = platelet aggregation
        2.platelets stick to each other
        3.forms platelet plug that closes small breaks
      - activated platelets release clotting compounds (ADP, clotting factors)
      - 15s after injury
    - 3.coagulation
      - 30s or more after injury, depends on clotting factors (procoagulants)
        procoagulants: Ca2+, 22 other proteins, inactive proenzymes converted to active enzymes that direct reactions in clotting response
      - fibrinogen -> fibrin
      - cascade
        chain reactions of 3 pathways
        extrinsic
        occurs when damaged cells release factor III
        produces lots of thrombin
        thrombin cleaves fibrinogen to fibrin
        intrinsic
        occurs during exposure to negatively charged molecules e.g. molecules on bacteria and lipids
        common
        begins with the activation of factor X by factor III
        converts prothombin (proenzyme) to thrombin
        thrombin converts fibrinogen to insoluble fibrin
        blood clot
        1)stimulates formation of factor III
        2)stimulates release of PF-3 platelets
        =3)form positive feedback loop that accelerates clotting process
        feedback control of blood clotting
        anticoagulants: enzymes that inhibit clotting)
        antithrombin-III
        heparin
        accelerates activation of antithrombin-III
        thrombomodulin
        activates protein C
        inactivates clotting factors
        stimulates formation of plasmin (breaks down fibrin)
        prostacyclin
        inhibits platelet aggregation
        oppose factors
  - Calcium ions
    - required in all 3 pathways
  - vitamin K
    - required for synthesis of 4 clotting factors
  - clot retraction
    - pulls torn edges of vessel closer together
      - reduces residual bleeding and stabilizes injury site
      - reduces damaged area, easier for fibroblasts, smooth muscle cells and endothelial cells to complete repair
  - fibrinolysis
    - gradual process of dissolving clot
    - thrombin and tissue plasminogen activator (t-PA) activate plasminogen, producing plasmin
      - plasmin digests fibrin strands
blood vessels
- arteries
  - carry blood away from heart
- veins
  - return blood to heart
- capillaries
  - interconnect smallest arteries and veins
  - exchange dissolved gases, nutrients and wastes between blood and surrounding tissues

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Descrição: Mapa Mental sobre Cardiovascular system, criado por Gillian C em 09-05-2019.
Criado por: Gillian C
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Cardiovascular system

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