As I recall the stressful experiences that I had, I remember the usual responses that my body exhibits during those moments. Some are shortness of breath and rapid breathing, rapid heart rate, and muscle contractions. These responses can be classified as part of the flight-or-flight responses, the first stage of the stress response, that were initiated by nerve impulses originating in the hypothalamus. The heart pumps blood vigorously to supply blood and oxygen to the brain and muscles while shortness of breath and rapid breathing occurs as a result of low oxygen levels in the body. These responses are prolonged through the secretion of epinephrine and norepinephrine hormones in the adrenal medulla. To be able to respond to stressors for long periods of time, the body goes into a resistance stage of the stress response initiated by the CRH, TRH, and GHRH secreted by the hypothalamus. These hormones are longer lasting, compared to the initial flight-or-flight response, and promote the breakdown of different macromolecules to provide ATP for counteracting stress.
References:
Tortora, G. J., & Derrickson, B. (2014). Chapter 18: The Endocrine System. In Principles of Anatomy and Physiology (14th ed.). Wiley.