The Stress ResponseThe Stress Response is the second part of the Stress and Health series. In this section we take a look at the mind and body's response to physical and psychological stress. Things happen very quickly in the brain and body when there is a perceived threat or stressor. Probably the best known of these responses is the flight-fright response. It stems from the days of "survival of the fittest". Individuals who was able to get away from predators and could act quickly when in danger were the one who lived on to reproduce and raise another generation. Today, most of us don't live under this constant threat, but a part of the subconscious brain, called the amygdala, remains on the job. It constantly scans our environment for danger, focusing on and finding problems that may threaten our survival. It does this by alerting us to danger when we face small conflicts and problems, turning them into big ones. For example, instead of letting insults or other ego threats go by, we respond by getting angry. This gets the stress response rolling. Yes, we all know people with "over-zealous" amygdalas, including ourselves sometimes! When the danger message is sent out, a complex chain of events takes place. It starts in the brain and sets off a multitudeof chemical reactions throughout the entire body. The Locus Coeruleus, a nucleus in the brain stem, sends the stress alert by increasing norepinephrine secretion.Different parts of the brain respond. Dopamine is released, exciting areas of the brain. Cognitive function and motivation improve. The brain is aroused and ready for action. A major part of the stress response is carried out by the Hypothalmic-Pituitary-Adrenal Axis (HPA axis)
The HPA axis is a part of the endocrine system that's under the control of the nervous system. It controls long-term reactions to stress. It regulates body processes including the immune system, sexuality, mood and digestion. It decides when you should store energy and where to send energy if more is needed. When norepinephrine is sent to the hypothalamus,it signals the pituitary gland. The pituitary gland sends a signal to the adrenal glands to release cortisol and androgens (weak steroids). Elevated cortisol levels due to chronic stress can have significiant long-term effects on your health. Members: Watch Dr. Lipton demonstrate this process in his Biology of Perception video located in the Members Area. Not a member yet? Join here. The autonomic nervous system responds even faster than the HPA. The ANS is responsible for the subconscious functioning of vital organ systems. During the stress response, norepinephrine signals the sympathetic part of the nervous system (SNS) to increase activity. Likewise, parasympathetic (PNS) activity decreases. The SNS sends a signal down the spinal cord to the adrenal glands to release adrenaline (epinephrine). It speeds up metabolism and provides extra energy. Digestive processes stop, breathing, heart rate and blood pressure go up. Blood flow to the skeletal muscles increases. Glucose (sugar) is released into the blood stream to fuel the muscles needed to run or fight. This is the classic flight-fright mechanism at work. To counter-balance the effects of the stress response, serotonin is released. The PNS releases acetylcholine by way of the largest nerve in the body, the vagus nerve. This nerve starts in the brain and extends to the organs. Taking a deep relaxing breath stimulates the vagus nerve and tells it to send a calming message.
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