6.4.1 principles of homeostasis

• describe homeostasis in mammals

  maintenance of a stable internal environment within restricted limits

  by physiological control systems (normally involve negative feedback)

  e.g core temperature, blood pH, glucose concentration, blood water potential
• 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 - hypoglycaemia)

  not enough glucose (respiratory substrate) for respiration

  so less ATP produced

  active transport (ect) cant happen so cell death
• explain the importance of maintaining stable blood glucose concentration (too high - hyperglycaemia)

  water potential of blood decreases

  water lost from tissue to blood via osmosis

  kidneys can't absorb all glucose so more water lost in urine causing dehydration
• describe the role of negative feedback in homeostasis

  receptors detect change from optimum

  effectors respond to counteract change

  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

  receptors detect change from normal

  effectors respond to amplify change

  producing a greater deviation from normal