Homeostasis U1AOS2

• Homeostasis


  The process that maintains the internal environment of an organism within set limits, to ensure proper functioning of cells, despite what else is going on in the world
• Stimulus-Response model


  • Stimulus - a change in the environment
  • Receptor - the stimulus is detected and translated into a chemical or electrical signal
  • Modulator - information from receptors is sent to a modulator, where they are compared to an ideal value. The modulator is often a part of the brain. The signal is sent back from the modulator to an effector
  • Effector - responds to the signal from the modulator
  • Response - the effector makes a change in response to the stimulus
• Positive feedback


  Occurs when the response increases the initial stimulus signal
• Negative feedback


  Occurs when the response reverses the initial stimulus signal
• Ways heat can enter or exit the body


  • Conduction
  • Convection
  • Evaporation
  • Radiation
• Metabolism


  The set of chemical reactions within cells that help maintain the body's normal functioning including converting food and drink to energy
• Thermoregulation


  The homeostatic process of maintaining a constant internal body temperature
• Endotherm


  An animal that produces the majority of its own heat via metabolic processes
• Ectotherm


  An animal that obtains heat primarily from the environment, rather than its own metabolic heat
• Regulating Body Temperature


  1. Stimulus - a change in core body temperature or the environmental temperature

  2. Receptor - thermoreceptors near the brain or in the skin detect temperature changes and send messages to the modulator

  3. Modulator - the hypothalamus

  4. Effector - sends messages to a variety of effector cells and tissues throughout the body

  5. Response - creates a change in heat transfer, helping to maintain a core body temperature of 37 °C
• Glucose


  A type of sugar that we get from the food we eat when carbohydrates are broken down by our digestive system. It is the main source of energy for the cells in our body.
• Hyperglycaemic


  When the blood glucose concentration is too high
• Hypoglycaemic


  When the blood glucose concentration is too low
• Glycogen


  Glucose can be stored in cells in this form
• Control of blood glucose


  1. Stimulus - change in blood glucose levels

  2. Receptor and Modulator - the pancreas

  3. Effector - insulin causes blood glucose to fall, glucagon causes blood glucose to increase

  4. Response - glucose moves into or out of the bloodstream and body cells
• Antidiuretic Hormone (ADH)


  Hormone released when water levels decrease, causing increased water reabsorption in the kidneys and a feeling of thirst
• Cells need to contain a certain amount of water for them to function correctly
• Our body needs water to produce urine, remove heat via sweat and maintain blood volume
• When water levels decrease, the concentration of solute in the blood will increase and blood pressure will decrease