b3

• The Nervous System


  Coordinates a response to what goes on around you
• The Central Nervous System (CNS)


  • Coordinates a response
  • Made up of the brain and spinal cord
• How the nervous system works

  1. Receptors detect a change in the environment

  2. Impulses are sent along neurones

  3. CNS decides the response

  4. Impulses travel along effectors

  5. Effectors carry out the response
• Neurones


  Transmit information as electrical impulses
• How neurones transmit information

  1. Electrical impulses pass along the neurone

  2. Neurones have branched endings to connect with other neurones

  3. Myelin sheath speeds up impulse transmission

  4. Impulses cross synapses via chemical signals
• Reflex actions


  Automatic responses that stop you injuring yourself
• How reflex actions work

  1. Receptor detects stimulus

  2. Impulses sent to CNS

  3. CNS sends impulses to effectors

  4. Effectors contract to move body part away
• Hormones


  Chemical messengers sent in the blood
• Endocrine glands


  • Pituitary gland
  • Pancreas
  • Ovaries
  • Testes
• Pituitary gland


  Releases hormones that act on other glands
• Pancreas


  Produces insulin to control blood glucose level
• Ovaries


  Produce oestrogen and progesterone
• Testes


  Produce testosterone
• The menstrual cycle


  1. Menstruation (day 1-4)

  2. Follicular stage (day 4-14)

  3. Ovulation (around day 14)

  4. Luteal stage (day 14-28)
• Hormones in the menstrual cycle

  • FSH stimulates ovary
  • Oestrogen thickens uterus lining
  • Progesterone maintains uterus lining
• Contraceptive methods


  • Hormonal (pills, implants, injections)
  • Non-hormonal (condoms, IUDs)
• Contraceptive methods


  • Hormonal methods more effective but can have side effects
  • Non-hormonal methods protect against STIs
• Insulin


  Controls blood glucose level
• Diabetes


  Condition where you can't control blood glucose level
• Types of diabetes


  • Type 1 (no insulin production)
  • Type 2 (cells don't respond to insulin)
• Individual


  A single organism
• Species


  A group of similar organisms that can interbreed
• Habitat


  The place where an organism lives
• Population


  All the organisms of one species in a habitat
• Community


  All the organisms of different species living in a habitat
• Ecosystem


  A community of organisms and their non-living environment
• Levels of organisation in an ecosystem

  1. Individual

  2. Population

  3. Community

  4. Ecosystem
• Organisms compete for resources

  • Plants need light, space, water, minerals
  • Animals need space, food, water, mates
• Competition between species


  One species is better at competing for resources, leading to decline of the other species