Final answer:
Cortisol is the hormone released from the adrenal cortex during stress as part of the HPA axis response. It prepares the body to face immediate threats but can weaken the immune system if levels remain high for prolonged periods.
Step-by-step explanation:
In the Hypothalamic-Pituitary-Adrenal (HPA) axis, a hormone that is released from the adrenals when we experience a stressful event is cortisol. During stress, the hypothalamus releases corticotropin-releasing hormone (CRH), which causes the pituitary gland to secrete adrenocorticotropic hormone (ACTH). ACTH then stimulates the adrenal cortex to produce cortisol, which has several effects on the body, including providing a burst of energy, temporarily improving immune function, and decreasing pain sensitivity. However, prolonged exposure to high levels of cortisol can have detrimental effects, such as weakening the immune system and increasing the risk of depression.
The adrenal glands also produce epinephrine and norepinephrine for the short-term stress response, leading to the fight-or-flight response which includes an increased heart rate, greater respiration, and other changes that prepare the body for immediate action.