biology chapter 4 gcse

• Coronary heart disease:

  • Layers of fatty acids build up inside coronary arteries, narrowing them and resulting in a lack of oxygen in the heart muscles
  • Stents are used to keep coronary arteries open but could lead to a blood clot
  • Statins are drugs that lower blood cholesterol levels, slowing down fatty material deposits but could also cause kidney or liver damage
• Heart valves:

  • Faulty heart valves can prevent opening fully or cause a leak and can be replaced with biological or mechanical valves
• Pacemakers:

  • Natural resting heart rate is controlled by a group of cells in the right atrium acting as a pacemaker
  • Artificial pacemakers are used to correct irregular heart rates but could lead to swelling or bleeding
• Heart transplants:

  • If heart failure occurs, a donor heart can be transplanted
• Artificial hearts:

  • Occasionally used to keep a patient awaiting a heart transplant alive, but it is expensive
• Plant tissues and organs:

  • Epidermal tissue covers the plant
  • Mesophyll tissue carries out photosynthesis
  • Xylem and phloem transport substances around the plant
  • Meristem tissue contains undifferentiated cells growing in root and shoot tips
  • Guard cells are adapted to close at night due to the absence of light for photosynthesis
• Transport in plants:

  • Transpiration rate is more rapid in hot, dry, windy, and bright conditions
  • Xylem tissue transports water and mineral ions through dead cells reinforced with lignin in the transpiration stream
  • Phloem tissue carries dissolved sugars from leaves to the rest of the plant in translocation
• Breathing and gas exchange:

  • The breathing system facilitates the exchange of oxygen and carbon dioxide in the bloodstream
  • Intercostal muscles contract, rib cage moves out and up, and the diaphragm becomes flatter for air to move into the lungs (ventilation)
• Blood and blood vessels:

  • Blood consists of plasma, red blood cells, white blood cells, and platelets
  • Veins have thin walls, carry blood under low pressure, and have a large lumen
  • Arteries have thick walls, a thick layer of muscle, and a small lumen
  • Capillaries have walls that are one cell thick and a narrow lumen
• The heart:

  • Deoxygenated blood enters the right atrium from the vena cava
  • Blood moves into the right ventricle
  • Blood is pumped into the pulmonary artery
  • The pulmonary artery carries deoxygenated blood to the lungs
  • Blood becomes oxygenated in the lungs
  • Oxygenated blood leaves the lungs via the pulmonary vein
  • Blood enters the left atrium
  • Blood moves into the left ventricle
• Arteries usually carry blood away from the heart
• Veins usually carry blood back to the heart
• Capillaries connect arteries and veins
• Alveoli are the site of gas exchange
• Epidermal covers the plant
• Palisade mesophyll is where most of the photosynthesis occurs
• Spongy mesophyll has air space for gases to diffuse easily
• Xylem transports water from roots to the rest of the plant
• Phloem transports dissolved sugars from leaves to the rest of the plant
• Meristem contains undifferentiated cells found at the growing tips of shoots and roots (stem cells)
• Leaf is where photosynthesis occurs
• Root absorbs water and mineral ions from the soil
• Flower are reproductive organs of the plant