Cardio 2

  • Created by: Mohsin
  • Created on: 08-04-18 14:46
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  • Cardio Therapeutics 2
    • Cardiac Anatomy
      • Double circulatory system
      • LV thicker muscle
        • Left side pumps blood into systemic circulation
          • Lots of resistance to flow which the heart has to overcome
      • Pressure is Pulmonary circulation LOWER than systemic
      • At rest blood flow = 5L/min
      • SYSTEMIC circulation
        • Arteries = carry oxygenated blood AWAY from the left side of the heart
        • Veins = carry de-oxygenated blood to the right side of the heart
        • Parallel - allows finer control of blood flow
          • Kidney - needs high blood flow to allow adequate excretion of urea
      • Distribution of cardiac output is not constant - changes to maintain internal environment
      • Most of the blood is held in the veins
    • Blood pressure (BP)
      • Normal BP = 120/80; sys/dia
      • Systolic = contraction
      • Diastolic = relaxation
    • Electrical conduction in the heart
      • SA generates AP (action potential)
        • Initiates rise in intracellular Ca+ which activates contraction
          • Causes depolarisation across the atria = contraction
            • Ventricles contract bottom upwards
      • At rest = 60/70 BPM
    • Myocardium and myocyte structure
      • Desmosomesjoin adjacent myocytes
        • Provide mechanical strength
        • Junction transmit ionic currents (electrical excitation) between myocytes
          • Gap made of protein (connexion) allows flow of ion
            • Ensures myocytes in ventricles activated together
      • Myocytes filled with myofibrils - consist if sarcomeres
        • T-tubules transmit electrical stimulus into cell - activate myofibrils
        • Shortening of sarcomere - contraction of the heart
    • Electro -cardiograph
      • P wave =  atrial fill with blood - atria depolarise
      • P-Q wave = atrial contraction
      • QRS wave = firing of AV node and ventricular de-polarisation
      • S wave = last phase of ventricular de-polarisation
      • ST wave = ventricles contract and eject blood
        • ST segment is isoelectric
          • If region of the ventricular myocardium is damaged by ischaemia (immediately after an MI)
            • causes ST elevation
            • in chronic myocardium ischaemia the ST segment is depressed
            • the myocyte in an ischaemic zone have:
              • smaller resting potential
              • smaller action potential
      • T wave = ventricular diastole
      • PR interval = time taken for excitation to spread through atria, AV node and His-Purkinje system into the ventricle
        • PR interval mainly caused by the delay at the AV node


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