Final answer:
Under acute stress, blood glucose levels increase as part of the fight-or-flight response, facilitated by adrenaline and cortisol. This physiological response is crucial for providing energy to meet the demands of the stressor. The HPA axis plays a key role in this process by stimulating gluconeogenesis and breaking down energy stores.
Step-by-step explanation:
In a person with a properly functioning Hypothalamic-Pituitary-Adrenal (HPA) axis, blood glucose levels should increase in response to an acute stressor such as encountering a predator. This elevation in blood glucose is part of the fight-or-flight response, a physiological reaction to stress. When the sympathetic nervous system is activated, it causes a release of adrenaline and cortisol, which together promote the breakdown of glycogen into glucose, increasing the availability of energy for the body to react.
The glucocorticoids such as cortisol have multiple roles. They promote gluconeogenesis—the production of glucose from non-carbohydrate sources—and stimulate the breakdown of fat and protein stores. These processes supply the body with the necessary fuel to manage the stressor, be it running away or confronting the danger.
Maintenance of blood glucose during stress is crucial as it provides the energy required by the body and particularly the brain, which is highly reliant on glucose. Therefore, during acute stress, the body has mechanisms like the HPA axis in place to ensure that energy levels are sufficient to meet the demands of the situation.