6.4.1 principles of homeostatis and negative feedback

describe homeostasis in mammals

maintenance of a stable internal environment within restricted limits

by physiological control systems (normally negative feedback)

examples of homeostasis in mammals

core temperature

blood pH

blood glucose concentration

blood water potential

what happens 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 E-S complexes

what happens if temperature is too low

not enough KE so fewer E-S complexes

explain the importance of maintaining a 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

whta happens if blood glucose conc. is too low

hypoglycaemia

not enough glucose for respiration

so less ATP produced

active transport can’t happen, cell death

what happens if blood glucose conc. is too high

hyperglycaemia

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

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

example of negative feedback in homeostasis

control of blood glucose concentration

blood pH

core temperature

blood water potential

explain the importance of conditions being controlled by separate mechanism involving negative feedback

departures in different directions from the original state can all be controlled

giving a greater degree of control

describe positive feedback

1. receptors detect change from normal

2. effectors respond to amplify change

3. producing a greater deviation from normal

examples of positive feedback

blood clotting