More biology

• The heart pumps blood around the body

  1. In a double circulatory system (two circuits joined together)

  2. Right ventricle pumps deoxygenated blood

  3. Left ventricle pumps oxygenated blood

  4. Right ventricle pumps blood into the lungs

  5. Left ventricle pumps blood to the body
• The atria contract


  1. Pushing the blood into the ventricles

  2. The ventricles contract

  3. Forcing blood out of the pulmonary artery and aorta
• Pulmonary artery


  Transports blood to the lungs where gas exchange takes place
• Natural resting heart rate


  Controlled by a group of cells in the right atrium that act as pacemakers
• Artificial pacemakers


  Electrical devices to control heartbeat if a person's natural ones do not operate properly
• Blood vessels


  • Arteries
  • Capillaries
  • Veins
• Arteries


  • Carry blood away from the heart
  • Have strong and elastic walls
  • Have thick walls compared to the lumen
  • Have thick layers of muscle to make them strong
  • Have elastic fibres to stretch and spring back
• Capillaries


  • Extremely small
  • Have a very small lumen
  • Have permeable walls one cell thick so substances can diffuse in and out
• Veins


  • Carry blood to the heart
  • Have a large lumen to help blood flow
  • Contain valves to keep blood flowing in the right direction
• Rate of blood flow

  Volume of blood per minute
• Blood


  A tissue consisting of plasma in which red blood cells, white blood cells and platelets are suspended
• Red blood cells


  • Carry oxygen
  • Have a biconcave shape for large surface area
  • Have no nucleus to allow more room for haemoglobin to bind to oxygen
• White blood cells


  • Defend against infection
  • Some change shape to engulf harmful microorganisms
  • Others produce antibodies and antitoxins to fight them
• Platelets


  • Help blood clot at a wound to prevent blood loss and microorganisms entering it
  • Are small fragments of cells
• Coronary heart disease


  When the coronary arteries (that supply blood to the heart) get blocked by layers of fatty material building up, restricting blood flow and causing a lack of oxygen for the heart
• Coronary arteries get blocked

  Higher risk of a heart attack
• Stents


  Keep the coronary arteries open, are effective for a long time and have a relatively quick recovery time
• Risks of stents

  • Heart attack
  • Infection
  • Blood clot
• Statins


  Drugs widely used to reduce blood cholesterol levels, preventing the rate of fatty material deposit
• Statins


  Prevent strokes, coronary heart disease, heart attacks and other diseases
• Statins


  • Long-term drug that must be taken regularly
  • Could cause kidney failure, liver damage or memory loss (negative side effects)
  • Take time to work
• Non-communicable diseases


  Risk factors can be aspects of a person's lifestyle or certain substances in their body or environment, and are often caused by the interaction of multiple risk factors
• Smoking


  Damages the walls of arteries, the lining of the lungs, and directly causes cardiovascular disease, lung disease and lung cancer
• Obesity


  Directly causes type 2 diabetes by making the body less resistant to insulin
• Alcohol


  Can cause liver disease and can damage nerve cells in the brain, causing it to lose volume
• Cancer


  Caused by changes in cells that lead to uncontrolled cell growth and division.
• Benign tumors


  • Contained in one area (usually within a membrane) and do not invade other tissues in the body, not cancerous
• Malignant tumors


  • Invade neighbouring healthy tissues and spread to different parts of the body through the bloodstream where they form secondary tumours, malignant cells are cancers
• Risk factors of cancer

  • Smoking
  • Obesity
  • UV exposure
  • Viral infections
• Waxy cuticle

  • Reduces water loss by evaporation
• Epidermal tissue


  • Transparent for light to pass through to the palisade layer
• Palisade mesophyll


  • Contains many chloroplasts to absorb light for photosynthesis
• Spongy mesophyll


  • Contains large air spaces which increases the rate of diffusion
• Lower epidermal tissue


  • Contains stomata to control the release or entry of gases into the leaf, controlled by guard cells
• Vascular bundles


  Network of xylem and phloem that delivers water and nutrients