Homeostasis & Response

• Homeostasis

  All of the processes that happen in a cell or organism to maintain (keep) conditions optimal
• Homeostasis is needed to respond to changes in the internal and external environment
• Enzyme functioning

  Humans must regulate their body's internal conditions to make sure their enzymes and cells function well
• Denaturing

  If conditions are not optimal, then our enzymes can denature (change shape), reducing their ability to catalyse (speed-up) metabolic reactions (chemical reactions in organisms)
• Conditions that need to be regulated

  • Internal body temperature
  • Urea concentration (in urine)
  • Water levels
  • Blood sugar levels
  • Carbon dioxide levels
• Control systems

  Use both nervous and chemical responses
• Parts of control systems

  • Receptors
  • Coordination centres
  • Effectors (muscles or glands)
• Receptors

  Receptor cells detect changes in the environment
• Coordination centres

  Receive and process information arriving from receptor cells
• Effectors

  Carry out responses to stimuli (events or things) that help to restore optimum levels
• Negative feedback

  The process that responds to changes in internal conditions away from the optimum and returns these conditions to their optimal range
• Detecting change

  1. When internal conditions are optimal, the body does not need to respond

  2. If an internal condition changes and is no longer optimal, the body detects this change using receptors
• Responding to change

  1. After a change has been detected, the body works to counteract (reverse) the change

  2. The change is reversed and conditions are returned to the optimum
• Negative feedback needs all of the components of the nervous system to work together
• Negative feedback process

  1. A stimulus (a change in the body) is detected by receptors

  2. Receptors relay the information to the central nervous system

  3. The CNS coordinates a response through effectors
• Nervous system

  Protects organisms from harm by responding to changes in the environment, coordinates communication between different parts of organisms
• Nervous system

  • Made up of the brain, the spinal cord, and neurones (nerve cells)
• Brain

  One of the components of the central nervous system (CNS), coordinates the response of effectors
• Effectors

  Muscles or glands that act in response to a change in the internal or external environment
• Spinal cord

  The other component of the CNS, important in coordinating the response of effectors to changes in the environment
• Neurones (nerve cells)

  Carry electrical impulses (signals) between receptors, the central nervous system (CNS) and effectors