Question

Identify which example below describes resetting of a set point

a. Decreased core body temperature causes arterioles of the skin constrict, reducing blood flow and heat loss across the skin.
b. Dehydration stimulates the feelings of thirst and the retention of water in the kidneys which together prevent further fluid loss.
c. When experiencing stress, the plasma levels of cortisol increase many times over baseline.
d. If the filtration rate of the kidneys increases, the kidneys release a chemical signal that decreases blood flow to the kidneys, which in turn reduces the filtration rate

Answer 1

The correct option that describes resetting of a set point is (c), where stress causes a significant increase in plasma levels of cortisol, indicating a new equilibrium point for hormonal balance. This is an example of the hypothalamus resetting the set point for cortisol levels in response to stress.

Step-by-step explanation:

The concept in question relates to the resetting of a biological set point, which is a central aspect of homeostasis. The resetting of a set point implies a change in the normal target range for a physiological function. In the given examples, only one describes a change in the set point itself, rather than simply a response to maintain homeostasis.

Option (c), where the plasma levels of cortisol increase significantly during stress, indicates a resetting of the hormonal balance, which suggests a new homeostatic set point is established during a stress response. This is an instance where the hypothalamus adjusts the set point for a physiological process (the level of cortisol) in response to stress, which is a change to the body's homeostatic balance.

The other options, namely (a), (b), and (d) describe the negative feedback mechanisms to maintain existing physiological set points rather than resetting them. For example, in option (a), vasoconstriction in cold conditions is part of the standard negative feedback response to maintain the preestablished body temperature set point, not to change or reset it.