Homeostasis

• Homeostasis


  The maintenance of a stable internal environment within set limits around an optimum, regardless of environmental conditions
• Importance of a stable core temperature


  • Maintain stable rate of enzyme-controlled reactions
  • Prevent damage to membranes
• Temperature too low


  Enzyme & substrate molecules have insufficient kinetic energy; leading to hypothermia
• Temperature too high


  Enzymes denature; So chemical reactions stop; Leading to hyperthermia
• Importance of stable blood pH


  • Maintain stable rate of enzyme-controlled reactions
  • Maintain optimum conditions for other proteins
• Acidic pH


  H+ ions interact with Hydrogen & ionic bonds in tertiary structure of enzymes → shape of active site changes so no Enzyme substrate complexes form
• Importance of stable blood glucose concentration


  • Maintain constant blood water potential: prevent osmotic lysis / crenation of cells
  • Maintain constant concentration of respiratory substrate
• Negative feedback


  Self-regulatory mechanisms return the internal environment to optimum when there is a fluctuation
• Positive feedback


  A fluctuation triggers changes that result in an even greater deviation from the normal level
• General stages involved in negative feedback

  1. Receptors detect deviation

  2. Coordinator

  3. Corrective mechanism by effector

  4. Receptors detect conditions have returned to normal
• Separate negative feedback mechanisms control fluctuations in different directions as it provides more control, especially in case of 'overcorrection', which would lead to a deviation in the opposite direction from the original one
• Coordinators analyse inputs from several receptors before sending an impulse to effectors because: Receptors may send conflicting information. Optimum response may require multiple types of effector