Biomedical research shows that the basic purpose of stress response is to make organisms adapt to the surrounding environment and make organisms respond to life-threatening challenges quickly and effectively. From struggle for existence's point of view, in the early days of animal kingdom and human society, stress response was called fight-or-flight response.
In order to escape danger, organisms will produce many physiological and psychological changes accompanied by stress response. This change can mobilize most of the body's energy, which can be immediately transformed into an appropriate form to deal with the enemy and transported to the most needed organs, especially the brain and major muscles. Therefore, when an organism is under stress, it will have the following similar physiological reactions:
(1) Shortness of breath and difficulty in breathing.
(2) Rapid heartbeat and thirst.
(3) Muscle tension, especially in the forehead, back neck, shoulders and elbows.
(4) frequent urination.
(5) Unconscious reactions, including increased gastric acid secretion, increased blood pressure, and changes in chemical composition in blood, such as increased blood sugar and cholesterol concentration.
These reactions are physical signs that the human body enters a state of tension. Stress response originates from the brain and coordinates the body through the brain. Individuals must first perceive the threat of external stimuli to health, which may involve many conscious and unconscious thoughts, beliefs, experiences, emotions and values. Many different parts of the brain play an important role in the whole information processing process, including the cerebral cortex and other higher nerve centers, which are automatically completed in an unconscious state, which is also the result of long-term evolution of organisms.
The two main biological systems that coordinate stress response are parasympathetic nervous system and hypothalamus-pituitary-adrenal system. The former connects the brain with other internal organs and transmits information to regulate basic functions such as respiration, heart rate and digestion, such as shortness of breath and dyspnea. In the process of stress reaction, bronchiectasis inhales extra oxygen to burn the energy in the body to meet the emergency needs of the body. A faster heartbeat means that the heart wants to output more blood to the brain and the main muscles of the body; Parasympathetic nervous system can cause involuntary urination and defecation. Although this method will make you have some extra activities when you are nervous, it can empty your bladder and large intestine, reduce the burden on your body and help you cope with stress.
The latter regulates the body's response by releasing hormones when the hypothalamus-pituitary-adrenal system is activated. Generally speaking, stress response includes a large number of electrical and chemical signals accumulated in the release of more than 30 chemical elements, including adrenaline, norepinephrine, cortisol, endorphins, thyrotropin, antidiuretic hormone, auxin and so on. All these have a wide range of biological effects on the target organs of the whole body, such as blood vessels, intestines, lungs, muscles, immune system and so on.