Final answer:
The sympathetic nervous system and the hypothalamic-pituitary-adrenal (HPA) axis are the two systems that work in tandem to control the body's responses to stress, mediating immediate and delayed reactions like the fight-or-flight response and cortisol release.
Step-by-step explanation:
The two systems in the body that work together to control the physical responses to stress are the sympathetic nervous system and the hypothalamic-pituitary-adrenal (HPA) axis. When confronted with stress, the sympathetic nervous system prompts immediate physical responses by releasing adrenaline from the adrenal glands, leading to the fight-or-flight response, which includes effects such as an increased heart rate and respiration. Simultaneously, the slower-acting HPA axis becomes active; it begins when the hypothalamus secretes corticotropin-releasing factor (CRF), leading to the release of adrenocorticotropic hormone (ACTH) by the pituitary gland, which in turn stimulates the adrenal glands to produce cortisol and other hormones. Cortisol, known as a stress hormone, provides a burst of energy to deal with stressors but can suppress the immune system when levels remain elevated for prolonged periods.