When the brain senses a stressor which system is activated?

When the brain senses a stressor, the hypothalamic-pituitary-adrenal (HPA) axis is activated. This triggers the release of stress hormones, primarily cortisol, from the adrenal glands. Additionally, the sympathetic nervous system is activated, leading to the "fight or flight" response, which prepares the body to respond to the perceived threat. Together, these systems facilitate both immediate and prolonged responses to stress.