Homeostasis

• Homeostasis


  Keeping a constant internal environment
• Four main conditions that needs to be controlled

  • Water
  • Ion levels
  • Body Temperature
  • Glucose
• Homeostatic control


  • The endocrine and central nervous systems are the major control systems for regulating homeostasis
  • The nervous system can detect deviation from the body's normal equilibrium (state of homeostasis) and sends messages to the affected organ to counteract this disturbance
  • Over a relatively short time it restores the required balance
• Kidneys


  Regulate water & mineral salts (ion) concentration
• Skin


  Regulate body temperature
• Liver & pancreas


  Regulate blood glucose level
• Parts of the body involved in Homeostasis

  • Kidney
  • Liver
  • Pancreas
  • Skin
  • Tissue cells
  • Blood
• How Homeostasis works


  1. To maintain optimal conditions in the body, there's need to monitor changes that occur

  2. A negative feedback control system responds when conditions change from the ideal or set point and returns conditions to this set point

  3. There is a continuous cycle of events in negative feedback
• Feedback


  • A loop system in which the system responds to perturbation either in the same direction (positive feedback) or in the opposite direction (negative feedback)
  • The Receptors are in the baroreceptor system located in the walls of certain arteries
  • The control centre is the medulla oblongata
  • The Effector is the cardiovascular system
• Changes due to temperature

  1. To keep warm: Shivering, Releasing energy from food, Vasoconstriction, Hairs stand on end

  2. To keep cool: Sweating which evaporates transferring heat to the environment, Vasodilation, Hairs lie flat

  3. Controlled by the hypothalamus in the brain
• Vasoconstriction


  A response to being too cold. The process involves the narrowing of blood vessels at the skin surface to reduce heat loss through the surface of the skin.
• Vasodilation


  A response to being too hot. The process includes the widening of blood vessels at the skin surface to increase heat loss through the surface of the skin.
• Thermoregulation


  • How we keep (or maintain) a steady body temperature
  • Our body temperature is 37°C, the temperature that our chemical reactions work best at
  • We must maintain it to prevent illnesses such as hypothermia and heat stroke
  • Being too hot or cold can lead to death
  • It is negative feedback as it restores temperatures to normal- any change has a response which counteracts it
• Blood Sugar-Glucose


  1. Blood sugar is maintained by two hormones secreted by the pancreas: insulin and glucagon

  2. Blood sugar rises after digestion of food

  3. In response, pancreas cells are stimulated to secrete insulin, which enables sugar uptake by cells and the storage of sugar in the liver and muscles

  4. In effect, insulin decreases blood sugar levels to normal
• The conditions inside your body need to be kept steady, even when the external environment changes
• Examples of conditions that need to be kept steady

  • Water levels
  • Core Body Temperature
  • Blood Glucose levels
• Homeostasis

  The maintenance of a stable internal environment