Bio Paper 2

• homeostasis 


  maintaining a stable internal environment (by regulating conditions inside the body as a response to internal and external conditions)
• give 3 automatic control systems

  receptors, coordination centres, effectors
• what do receptors do


  detect a change
• what do co-ordination centres do?

  interpret and decide what needs to be done about the change
• what are effectors?


  muscles or glands which carry out change by contracting or secreting hormones
• nervous system


  very fast electrical impulses through nerves
• endocrine system


  slower, longer lasting, using hormones in bloodstream
• negative feedback


  does the opposite of the change
• how does negative feedback regulate (eg blood pressure)

  receptor detects high blood pressure and sends a signal to coordination centre. This processes info and simulates effector. the effector produces a response to (decrease blood pressure)
• sensory neurones


  carry information from receptors to central nervous system, for example temperature changes or CO2 levels in blood
• Motor neurones


  after the central nervous system has decided what to do about information, it sends impulses back out to the body by motor neurones to effectors.
• relay neurone


  inside spinal chord, passes impulses from sensory to motor neurones
• Thyroxine

  • produced by thyroid in the neck
  • helps to regulate metabolism, heart rate and temperature
• adrenaline

  • produced by adrenal glands near kidneys
  • prepares body for a fight or flight response
• insulin

  • produced by pancreas
  • regulated blood glucose levels
• what does the pituitary gland do?

  produces many hormones which regulate body conditions. These hormones act on other glands to bring about change
• Oestrogen

  • produced in the ovaries
  • involved in menstrual cycle
• Testosterone

  • produced by testes
  • controls puberty and sperm production in males
• why are people with type 1 diabetes encouraged to exercise regularly?

  because muscles absorb more glucose from the blood when exercising
• why does type 2 diabetes occur?

  insulin resistance, so cells won’t take in so much glucose from the bloodstream
• why does type 1 diabetes occur?

  they can’t regulate blood glucose
• describe what happens to excess glucose in the blood.

  moves into the liver and muscle cells and then is converted into glycogen for storage
• what effect does insulin have on liver cells


  it stimulates them to store glucose as glycogen
• where do glands release hormones to

  into the bloodstream
• what is the definition of a hormone

  a chemical messenger produced by a gland which travels to its target organ through the blood
• where is luteinising hormone produced

  pituitary gland
• what does luteinising hormone do

  stimulates the release of an egg
• what does Follicle Stimulating Hormone do


  causes the egg to develop
• why can we use oestrogen to prevent release of an egg?

  because high levels of it (every day) inhibits FSH
• why can we use Progesterone to reduce fertility?

  produces thick mucus which prevents sperm reaching egg
• what does the oral pill contain

  oestrogen and progesterone
• what does the contraceptive patch contain

  oestrogen and progesterone
• what is a contraceptive implant?

  • releases continuous progesterone
  • stops ovaries producing eggs
  • lasts for up to 3 years
• contraceptive injection contains?


  progesterone
• what does an IUD do?

  kills sperm and prevents a fertilised egg from implanting
• what is the name of a substance which kills sperm

  spermicide
• cons of fertility drugs

  low success rate, unexpected multiple births
• what do low levels of FSH mean?

  eggs cannot mature, so no eggs are released and the woman cannot become pregnant
• why would a couple use Intra-cytoplasmic sperm injection? (sperm injected straight into egg)

  if the man has a low sperm count
• cons of IVF

  • multiple births can occur
  • only 26% success rate
  • some women have strong side effects for hormones taken like abdominal pain and vomiting