5 physiological responses of the human body to stress
Stress (biology) Physiological or biological stress is an organism's response to a stressor such as an environmental condition. Stress is the body's method of reacting to a challenge. Stimuli that alter an organism's environment are responded to by multiple systems in the body. The autonomic nervous system and hypothalamic-pituitary-adrenal (HPA) axis are two major systems that respond to stress. The sympathoadrenal medullary (SAM) axis may activate the fight or flight response through the sympathetic nervous system, which dedicates energy to more relevant bodily systems to acute adaption to stress, while the parasympathetic nervous system returns the body to homeostasis. The second major physiological stress, the HPA axis regulates the release of cortisol, which influences many bodily functions such as metabolic, psychological and immunological functions. The SAM and HPA axes are regulated by a wide variety of brain regions, including the limbic system, prefrontal cortex, amygdala, hypothalamus, and stria terminalis.[1] Through these mechanisms, stress can alter memory functions, reward, immune function, metabolism and susceptibility to diseases.[2] Definitions of stress differ; however, one system proposed by Elliot and Eisdorfer suggests five types of stress. The five types of stress are labeled "acute time limited stressors", "brief naturalistic stressors", "stressful event sequence", "chronic stressors", and "distant stressors". Acute time limited stressors involve short term challenges, while, on the other hand, brief naturalistic stressors involve an event that is normal but nevertheless challenging. Stressful event sequences are a stressor that occur, and continue to yield stress into the immediate future. Chronic stressors involve exposure to a long-term stressor and a distant stressor is a stressor that isn't immediate.[3]
Fight-or-flight response The reaction begins in the amygdala, which triggers a neural response in the hypothalamus. The initial reaction is followed by activation of the pituitary gland and secretion of the hormone ACTH.[9] The adrenal gland is activated almost simultaneously, via the sympathetic nervous system, and releases the hormone epinephrine. The release of chemical messengers results in the production of the hormone cortisol, which increases blood pressure, blood sugar, and suppresses the immune system.[10] The initial response and subsequent reactions are triggered in an effort to create a boost of energy. This boost of energy is activated by epinephrine binding to liver cells and the subsequent production of glucose.[11] Additionally, the circulation of cortisol functions to turn fatty acids into available energy, which prepares muscles throughout the body for response.[12] Catecholamine hormones, such as adrenaline (epinephrine) or noradrenaline (norepinephrine), facilitate immediate physical reactions associated with a preparation for violent muscular action andÂ :[13]