Principles of Homeostasis and Negative Feedback

• What is Homeostasis?

  Maintenance of a constant internal environment around a set point using negative feedback
• Explain the importance of maintaining stable core temperature:

  ● If temperature is too high:

  ○ Hydrogen bonds in tertiary structure of enzymes break

  ○ Enzymes denature; active sites change shape and substrates can’t bind

  ○ So fewer enzyme-substrate complexes

  ● If temperature is too low:

  ○ Not enough kinetic energy so fewer enzyme-substrate complexes
• Explain the importance of maintaining stable blood pH:

  ● Above or below optimal pH, ionic / hydrogen bonds in tertiary structure break

  ● Enzymes denature; active sites change shape and substrates can’t bind

  ● So fewer enzyme substrate complexes
• Explain the importance of maintaining stable blood glucose concentration (Too low):

  ● Not enough glucose (respiratory substrate) for

  respiration

  ● So less ATP produced

  ● Active transport etc. can’t happen → cell death
• Explain the importance of maintaining stable blood glucose concentration (Too High):

  ● Water potential of blood decreases

  ● Water lost from tissue to blood via osmosis

  ● Kidneys can’t absorb all glucose → more water

  lost in urine causing dehydration
• What is Negative Feedback?

  End point of a process inhibits process
• Describe the role of negative feedback in homeostasis:

  1)Receptors detect change from optimum

  2)Effectors respond to counteract change

  3)Returning levels to optimum / normal
• Explain the importance of conditions being controlled by separate

  mechanisms involving negative feedback:

  ● Departures in different directions from the original state can all be controlled / reversed

  ● Giving a greater degree of control (over changes in internal environment)
• Describe positive feedback:

  1)Receptors detect change from normal

  2)Effectors respond to amplify change

  3)Producing a greater deviation from normal