Sympathetic Nervous System (SNS)
Definition - What does Sympathetic Nervous System (SNS) mean?
The Sympathetic Nervous System (SNS) is a division of the Autonomic Nervous System (ANS), responsible for many of the body's regulatory mechanisms. Otherwise known as the 'fight or flight response,' the SNS is activated when the brain perceives threat, danger or stress.
SNS activation results in increased heart rate and blood pressure, as well as secretion of hormones, such as adrenaline and epinephrine. Energy levels are elevated, digestion slows, muscles tighten and blood flow to the extremities is decreased. These reactions rapidly prepare the body for imminent danger, creating the conditions necessary to fight or run away.
Yogapedia explains Sympathetic Nervous System (SNS)
SNS activation is an automatic response, operating through a system of neurons in the spinal cord. Without conscious direction, the SNS harmonizes with the other division of the ANS, called the Parasympathetic Nervous System (PNS). Generally, the two systems work together to create homeostasis, essentially balancing the body's regulatory mechanisms.
Chronic stress caused by modern living tends to result in long-term over-stimulation of the SNS. The day-to-day challenges we face get misinterpreted by the brain as life-threatening, sounding the body’s alarm whether we are faced with a tiger or a traffic jam. Over time, the physiological reactions of repeated SNS activation can take their toll on overall health, leading to a variety of disorders and illnesses such as high blood pressure, asthma and autoimmune disease.
The way to counter over-stimulation of the SNS is to regularly activate the PNS. This can be done through practices such as yoga, meditation, mindfulness, pranayama, Tai Chi and Qigong, as well as simple deep breathing and guided relaxation techniques. With regular practice, it is possible to rebalance the divisions of the ANS.