Homeostasis

• What is homeostasis ?

  When the internal environment is maintained within set limits around the optimum.
• Why is it important to keep temperature controlled ?

  Because it affects enzyme activity, diffusion, osmosis and nerve transmission.

  Too high = enzymes denature

  Too low = enzymes and substrates have an insufficient amount of kinetic energy
• Why is it important to control glucose concentration ?

  Respiratory substances, for growth and repair, maintains blood water potential
• Why is it important to control CO2?

  CO2 lowers pH affecting enzyme action
• Why is it important to control water potential ?

  Dehydration, thickening of blood, increased blood pressure, affects water potential.
• Why is it important to control the pH ?

  To maintain a stable environment for enzyme controlled reactions.

  Too low = Hydrogen bond and ionic bonds break, altering the tertiary structure which means the active site is no longer complementary so no E-S complexes can form.
• What is positive feedback ?

  When a stimulus is detected and the change is amplified. The system will only revert back to normal once the stimulus has been removed.
• How is blood clotting an example of positive feedback ?

  When you get a cut, platelets become activated and release a chemical which triggers more platelets to be activated, and so on. This means platelets form a blood clot very quickly.
• What is negative feedback ?

  A system which detects when the value of a factor has falls outside of its range and activates mechanisms to bring it back within range.
• Outline the general stages involved in a negative feedback loop.

  Stimulus -> Receptors -> Coordinating system -> Effector -> Receptors monitor the stimulus
• What structure in the brain controls your body temperature ?

  hypothalamus
• What is glucoregulation ?

  Regulation of blood glucose concentration.
• What is glucose stored as ?

  glycogen
• What cells are islets of langerhans made up of ?

  Alpha and beta cells
• What two factors mainly affect the concentration of glucose ?

  Eating carbohydrates and exercise