The Circulatory System

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  • The Circulatory System
    • Single-celled organisms
      • Diffusion -quick because of short distance
    • Multicellular organisms
      • Mass transport system
        • Carry raw material from specialised support organs
        • Remove metabolic waste
    • Heart pumps blood
      • Right side- deoxygenated blood to lungs
      • Left side- oxygenated blood to the whole body
        • Left ventricle has thicker, more muscular walls than right ventricle
          • Because it needs to contract powerfully to pump blood all around body, -whereas right side is only to lungs
        • Ventricles have thicker walls than atria
          • Because they need to push blood out of heart
      • AV valves
        • Prevent back-flow  of blood from ventricles to the atria
        • Open one way
          • SL valves
            • Prevent back-flow blood from arteries to ventricles (when ventricles contract)
      • SL valves
        • Prevent back-flow blood from arteries to ventricles (when ventricles contract)
    • Blood vessels
      • Arteries
        • Carry blood from heart to the rest of the body
        • Thick-walled, muscular and have elastic tissue in walls
          • Cope with high pressure caused by heartbeat
        • Endothelium folded
          • Allows artery to exapnd and cope w/ high pressure
      • Veins
        • Take blood back to the heart
        • Larger lumen than arteries
        • Little elastic/ muscle tissue
        • Valves- to prevent back-flow of blood
        • Contraction of surrounding body muscles allow blood flow
      • Capillaries
        • Smallest blood vessel
        • where metabolic exchange occurs
        • Network of capillaries in tissue- capillary beds
          • Increase surface area
        • One cell thick
          • Increases speed of diffusion
    • Cardiac cycle
      • Ventricular diastole & atrial systole
        • Ventricles relaxed and atria contract
          • Decreases volume and increases pressure in chamber
            • Contracing atria pushes blood into ventricles
              • Increase in ventricular pressure and chamber volume
      • Ventricular systole & atrial diastole
        • Atria relax and ventricles contract
          • Decreasing volume and increasing pressure
            • Pressure higher in ventricles than atria, so AV valves shut to prevent back-flow
            • Pressure also higher in ventricles than in pulmonaryartery and aorta, so SL valves open, forcing out blood
      • Ventricular and atrial diastole
        • Both relax
        • Higher pressure in pulmonary artery and aorta causes SL valve to shut (prevent back-flow into ventricles)
        • Blood returns to heart, and arteries fill again due to the higher pressure in vena cava and pulmonary vein
          • As ventricles continue to relax, pressure falls below pressure of atria, and so AV valves open
            • This causes blood to flow passively from atria to ventricles
        • Atria contract, and whole process starts again
    • Daphnia experiment
      • Ethical issues with using invertebrates
        • Scientists can do experiments on animals to study things which would be unethical to do on humans
        • Others could argue it's unethical to do on animals
          • They can't give consent
          • They could be put through painful procedures
        • Some people believe it is more acceptable to do experiments on invertebrates rather than animals
          • Because the're considered to be simpler organisms, with less sophisticated nervous systems, so may feel less or no pain
            • They're also less distant to humans
        • Although some people may argue it is unethical to put any organism through suffering or distress
          • Subjecting them to extreme temperature or depriving them of food

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