B5

• Homeostasis consists of automatic control systems making sure the bodies internal conditions stay consistent
• automatic control system

  • receptor cells: detect changes in the environment
  • stimulus: change to the environment
  • co-ordination centre: receives and processes information
  • effector: carries out the responce
• Central nervous system (CNS) is the brain and spinal cord.
• neurone: nerve cell
• Sensory neurones carry messages from receptors to co-ordination centres
• Neurones are specialised cells that transmit electrical impulses along their length, from one neurone to another or between a neurone and an effector organ.
• Motor neurones carry messages from co-ordination centres to effectors
• Required practical- reaction time

  • test is repeated several times so a mean is calculated
  • test is repeated on another person
• independent variable: what is changed
• dependant variable: measured for each change
• control variable: what stays the same
• endocrine system is a system of glands that secrete hormones into the bloodstream
• placement of glands: pancreas ovaries testes thyroid adrenal pituitary
• glucose

  • monitored by pancreas
  • if too high insulin is released
  • muscle cells and the liver store extra glycogen
• type 1 diabetes: pancreas does not produce enough insulin

  • insulin injections after meals
• type 2 diabetes: body cells do not respond to insulin

  • restricted diet
  • obesity factor