Organisation

• Double circulatory system


  Blood is pumped by the heart twice - once to the lungs, once to the body
• Function of the heart

  • Right side pumps deoxygenated blood to the lungs to become oxygenated
  • Left side pumps oxygenated blood around the body
• Heart contraction


  1. Blood from vena cava and pulmonary vein fills the atria

  2. Contractions in the atria increase pressure and push blood into the ventricles

  3. Contractions of the ventricles increase pressure and push blood out of the heart into the pulmonary artery and aorta
• Heart valves


  Keep blood flowing in the correct direction and stop backflow
• Pacemaker


  Small group of cells in the right atrium that initiate contraction
• Smaller organisms have a single circulatory system where blood passes through the heart, to gills, then distributed to the body
• Levels of organisation


  • Cell
  • Specialised tissue
  • Organ
  • Organ system
  • Organism
• Larger organisms require a circulatory system to deliver nutrients and oxygen to cells
• Functions of blood


  • Transport
  • Protection
  • Regulation
• Components of blood


  • Plasma (55%)
  • Red blood cells (45%)
  • White blood cells
  • Platelets
• Plasma


  Fluid part that carries the blood cells and dissolved substances
• Red blood cells


  Only human cell without a nucleus, carry oxygen using haemoglobin
• White blood cells


  Help defend against diseases
• Platelets


  Help the blood to clot
• Arteries


  • Thick elastic layer to withstand high pressure
  • Small lumen
  • Thick walls with muscle and elastic fibres
• Capillaries


  Thin walls allow diffusion of nutrients and oxygen
• Functions of blood vessels

  • Arteries - carry blood away from the heart
  • Veins - carry blood back to the heart
  • Capillaries - form a network to allow substances to pass between cells and blood
• Heart valve problems


  Can become leaky over time, reducing heart efficiency and causing breathlessness
• Heart rate and pacemaker

  Pacemaker cells in the right atrium initiate contractions, but these cells lose ability to contract regularly as you get older
• Artificial pacemaker


  Wires threaded into the heart to electrically stimulate regular contractions
• Coronary heart disease


  Lumen of coronary arteries narrowed by fatty deposits (cholesterol)
• Risk factors for coronary heart disease

  • High fat diet
  • Lack of exercise
  • Hereditary (genes)
• Symptoms and effects of coronary heart disease

  Lack of blood supply makes exercise difficult, can cause muscle tissue to die and lead to heart attack
• Statins


  Drugs that lower blood cholesterol, slowing plaque build-up but not reversing existing plaque
• Stents


  Used to mechanically increase the width of the artery lumen
• Heart failure


  Heart can't pump enough blood to meet the body's needs, often requiring a heart transplant
• Non-communicable disease


  Disease not caused by a pathogen that cannot be spread from one organism to another
• Mortality data


  Describes the causes of death in a population, showing non-communicable diseases are responsible for the majority of deaths
• Hazard


  Something with the potential to cause harm, e.g. a Bunsen burner
• Risk


  The probability that a hazard may cause harm, e.g. risk of burns from using a Bunsen burner
• Risk factors


  • Lifestyle choices that increase the chances of developing a disease, e.g. smoking for cancer
• High fat diet


  Increases cholesterol in the blood
• Lack of exercise


  Means cholesterol remains high, increasing chances of build-up in coronary arteries
• What are the basic building blocks of all living organisms?

  Cells
• What happens to cells as an organism develops?

  Cells differentiate to form specialized types
• When do most types of animal cells differentiate?

  At an early stage of development
• What is the primary function of mature animal cells?

  Cell division and repair
• What changes occur as a cell differentiates?

  Shape changes and new structures develop
• Name three specialized animal cells.

  Sperm, nerve, and muscle cells
• What is the function of the tail in a sperm cell?

  To propel the sperm to fertilize the egg