Have you ever felt your heart racing before a big presentation or sensed a surge of energy when you see something frightening? This is the fight or flight response, which is masterminded by the sympathetic nervous system, says Dr Rohit Pai, consultant neurologist, Kasturba Medical College, and Hospitals, Mangaluru. “This response helps prepare a person to avert any danger,” he explains.
The sympathetic nervous system forms one part of the autonomic nervous system. The autonomic system regulates processes in the body that we do not consciously think about, such as breathing, digestion, and heartbeat. It has nerves that sends signals to the intestines, heart, salivary glands, pupils, lungs and genitals.
Preparing to tackle
Just like how you kick start the bike to get the engines running, the sympathetic nervous system increases blood flow to heart, muscles and brain to help the person think and run away from the danger. Dr Pai says that certain neurons of this system release noradrenaline. This neurochemical redirects the blood flow and also accelerates heart rate, blood pressure and inhibits digestion.
Dr Pai explains that there are certain conditions that specifically affect the sympathetic nerves. These include diabetes, anxiety disorders, chronic pain, adrenal tumours, hyperhidrosis (excessive sweating), and gastroparesis (trouble digesting).
All these conditions often cause or are a result of the prolonged hyperactivated fight or flight response. To balance out the revved-up effects of the sympathetic nervous system, the parasympathetic nervous system exerts relaxing effects to bring the body back to its regulated state. “If there is an imbalance between these two systems, it may result in increased morbidity and mortality,” Dr Pai says.
This infographic shows what the sympathetic nervous system does to prepare the body for a stressful situation.
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