AQA biology 5.3 heart disease

Atheroma
1. start as fatty streaks of white blood cells that take up LDL's
  1. LDL = low-density lipoproteins
  2. grows and forms and atheromatous plaque
    1. made up of cholesterol, fibres and dead muscle cells
      1. bulges into lumen of artery
        this narrows the artery
        this reduces the blood flow
        this increases risk of aneurysm and thrombosis
thrombosis
1. when an atheroma breaks through the lining of a blood vessel.
  1. this rough surface interrupts smooth blood flow
    1. this leads to formation of a thrombus (blood clot)
      1. this thrombus may block blood vessels
        this reduces/prevents blood flow to tissues beyond
        tissue deprived of blood often dies
        this is due to lack of oxygen and glucose and other nutrients.
        sometimes, they are carried by the blood and become lodged in another artery
aneurysm
1. form because atheromas weaken artery walls.
  1. weakened points swell to for a balloon-like structure
    1. these are filled with blood
      1. this is the aneurysm
        they frequently burst
        this causes a haemorrhage
        this causes a loss of blood to the region of body served my that artery
        a brain aneurysm is known as a cerebrovascular accident (CVA)
        better known as a stroke
myocardial infarction
1. commonly known as a heart attack
  1. reduced supply of oxygen to the heart muscle
    1. result of blockage in coronary arteries
      1. blockage close to junction of aorta and coronary artery will stop the heart
        because blood supply will be completely cut off
      2. blockage further down coronary artery, symptoms are milder
        because a smaller area of the muscle will suffer oxygen deprivation
risk factors
1. smoking
  1. carbon monoxide
    1. combines easily to haemoglobin
      1. forms carboxyhaemoglobin
        reduces oxygen-carrying capacity of haemoglobin
        to supply sufficient oxygen to tissues, the heart has to work harder
        this leads to raised blood pressure
        this increases risk of CHD and strokes.
        can also cause insufficient supply of oxygen to heart during exercise
        this leads to chest pain and in severe cases, a myocardial infarction
        chest pain is know as angina
  2. nicotine
    1. stimulates production of adrenaline
      1. this increases heart rate and raises blood pressure
        this increases risk of CHD
    2. makes red blood cells 'sticky'
      1. makes them coagulate
        higher risk of thrombosis, hence strokes or myocardial infarction
2. high blood pressure
  1. can be due to genes
  2. there are lifestyle factors
    1. prolonged stress
    2. certain diets
    3. lack of exercise
  3. high pressure in arteries makes them more likely to develop an aneurysm and burst
  4. to resist higher pressure, artery walls thicken and harden, restricting blood flow
3. blood cholesteral
  1. high-density lipoproteins
    1. remove cholesteral and transport it to liver for excretion
      1. help protect arteries from heart disease
  2. low-density lipoproteins
    1. transport cholesterol from liver to tissue
      1. this infiltrates and builds up in artery walls
        this leads to the development of atheromas
4. Diet
  1. high levels of salt
    1. raises blood pressure
  2. high levels of saturated fat
    1. increase LDL's
      1. this increases blood cholesterol concentration

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AQA biology 5.3 heart disease

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