Lifestyle, Health and Risk (Section 1, Topic 1)

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  • Lifestyle, Health and Risk: Topic 1
    • Circulation
      • Multicellular organisms are too large for substances to diffuse through their skin and to reach all their cells quickly enough
        • Substances need to be moved through mass flow
          • Substances are carried in the blood
        • Circulation of body fluid in insects and other small animals is mainly in the body cavities surrounding organs
          • Diffusion of substances in and out of cells in these organs is only efficient over small distances
    • Water
      • Water is a very good solvent so it can dissolve many different types of substances
        • Each water molecule consists of two hydrogen atoms joined to one oxygen atom
          • The electrons are not evenly spread, which results in the oxygen atom having a negative charge and the hydrogen atoms having a positive charge
      • Water has a high specific heat capacity meaning that it is slow to warm up and cool down
      • Molecules that will readily mix with water are salts, sugars and many proteins
        • Ioinic compounds dissolve in water because the small negative charges at the oxygen end of the water molecules are attracted to the positive ions and surround them
          • Examples of hydrophilic molecules are sugars (OH groups) and amino acids (NH2 groups)
    • Cardiac Cycle
      • Phase 1 : Atrial Systole -     Blood returns to the heart. Blood under low pressure flows into the left and right atria from the pulmonary veins and vena cava
      • Phase 2: Ventricular Systole - After a slight delay, the ventricles contract from the base of the heart upwards, increasing the pressure in the ventricles. The pressure forces open the SL valves and pushes blood through the pulmonary arteries and aorta
      • Phase 3: Cardiac Diastole - The atria and ventricles relax. Elastic recoil of the relaxing heart walls lowers the pressure in the atria and the ventricles. Blood under high pressure in the pulmonary arteries and aorta is drawn back towards the ventricles, closing the semilunar valves and preventing further backflow to the ventricles
    • Atherosclerosi-s
      • Atherosclerosis is a narrowing of an artery due to deposits of cholesterol and formation of plaques
      • The endothelium which lines the artery becomes damaged
        • White blood cells move into the damaged artery wall and cause cholesterol to be deposited n the artery wall to form an atheroma
          • A plaque then forms from deposited calcium salts and fibrous tissue
            • Atheroma's and plaques partially block arteries increasing blood pressure and leading to risks of heart disease and strokes
    • Topic 5
      • When platelets come into contact with the damaged vessel wall, they change from flattened discs to spheres with long projections
        • Clotting cascade
          • 1. Platelets and damaged tissue release thromboplastin
          • 2. Thromboplastin activates an enzyme that catalyses the  conversion of the protein thrombin into an enzyme called thrombin
            • Vitamin K and Calcium ions must be present
          • 3. Thrombin catalyses the conversion of soluble plasma protein fibrinogen to insoluble fibrin
          • 4. Fibrin creates a mesh forming a blood clot


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