Homeostasis and response

• Homeostasis is maintaining a stable internal environment
• Homeostasis


  Maintaining a Stable Internal Environment
• The body needs to be kept at the right conditions for it to function properly
• Control system


  Made up of receptor, coordinator (brain and nerves) and effector
• Negative feedback


  1. Detects change

  2. Processes information

  3. Effector produces response to counteract change

  4. Restores optimum level
• Negative feedback stops things getting out of balance
• The central nervous system coordinates the response
• Receptors and effectors form part of the control system
• Reflexes bypass the central nervous system
• Reaction time can be measured by a computer
• The brain controls many functions of the body
• The eye responds to light
• There are treatments available for vision defects
• The body has mechanisms to control its temperature
• The endocrine system uses hormones to control the body
• Nerves and hormones have different effects
• Blood glucose levels are controlled by the body
• The kidneys control the concentration of urine
• Kidney transplants can be rejected
• Puberty and the menstrual cycle are controlled by hormones
• IVF can help couples have children
• There are other ways to avoid pregnancy
• Adrenaline and thyroxine are released by negative feedback
• Plant hormones control plant growth and development
• Gibberellin stimulates plant stems to grow
• Ethene stimulates the ripening of fruit
• Commercially, ethene can be used to speed up or delay fruit ripening