6.4.1 Principles of homeostasis and negative feedback

Question 1

Homeostasis

Answer 1

Homeostasis in mammals involves physiological control systems
that maintain the internal environment within restricted limits.

Question 2

Why is homeostasis important?

Answer 2

It is important to maintain a stable core temperature and
stable blood pH to optimize enzyme activity.
It is important to maintain a stable blood glucose
concentration because (a) glucose is a respiratory substrate and needs to remain available and (b) glucose is a solute and so affects
the water potential of blood.

Question 3

Negative feedback

Answer 3

Negative feedback restores systems to their original level. A departure from an original state triggers a response which reduces the effect of the departure, because any deviation of the state from its norm initiates a corrective mechanism.

The possession of separate mechanisms involving negative
feedback in different directions from the original state (ie a having one mechanism for reversing increases and another for reversing decreases) gives a greater degree of control.

Question 4

Positive feedback

Answer 4

Positive feedback happens when a departure from an original state triggers a mechanism which results in further change in the same direction.