homeostasis

Question 1

define homeostasis

Answer 1

the maintenance of a constant internal environment ensuring reactions continue at a constant and appropriate rate allowing cells to function normally despite changes in the external environment

Question 2

define negative feedback

Answer 2

a change in a system which produces a second change which reverses the first change

Question 3

outline the process of negative feedback

Answer 3

1) a receptor detects the level of the factor and its deviation from a set point
2) the receptor sends instructions to a co-ordinator or controller
3) the co-ordinator communicates with one or more of the effectors such as glands which alter responses to be correct
4) the factor then returns to normal which is fed back to the effectors to stop making the change

Question 4

provide some examples of negative feedback mechanisms

Answer 4

1) glucose concentration in the plasma- as it increases above set point insulin is secreted reducing its concentration, if levels fall below a set point glucagon increases the conc
2) body temp- if it falls below a certain point increasing respiration generates heat and constriction of blood vessels retains it

Question 5

what is positive feedback

Answer 5

when the effector increases the original change - so when there is movement away from the set point the effector causes even more movement away rather than returning back to normal

Question 6

give some examples of positive feedback

Answer 6

1) oxytocin stimulates the contraction of the uterus, the contractions cause the release of even more oxytocin which stimulates even more contractions