How well do you really know your nervous system?

The human nervous system can be understood simply as a sort of command center of the body. Through a complex network of electrical impulses, we sense, process, respond to, and act upon stimuli that allow us to engage in life.

The nervous system is divided into two primary subdivisions:

• the central nervous system: composed of the brain and the spinal cord

• the peripheral nervous system: composed of the somatic and autonomic nervous systems

The somatic nervous system controls voluntary input and output, including sensation and movement.

The autonomic nervous system controls automatic functions of the body and can be further divided into the sympathetic and parasympathetic nervous systems (and some researchers include the enteric nervous system as a third subdivision).

The sympathetic nervous system is primarily responsible for the fight-or-flight response to stress. Through cascading events in response to a stressor, an acute stress response is elicited. If your brain interprets the stressor to be a legitimate threat then the stress response is sustained and your body prepares for action by diverting, oxygen-rich blood towards your extremities, by increasing your heart rate, respiration rate, and blood pressure. The stress response happens relatively quickly and can even occur before you are consciously aware that a stressor is present. Some individuals have a hyperactive sympathetic nervous system, resulting from chronic stress that can be related to a whole host of physiological and emotional symptoms, including high blood pressure and digestive issues.

The parasympathetic nervous system, the antagonist of the sympathetic nervous system, has the primary function of promoting rest and digestion. While the sympathetic nervous system increased heart rate and respiration rate and put a pause on any nonessential or restorative functions, the parasympathetic nervous system allows us to digest, recover and rest by lowering heart rate, respiration rate, and blood pressure, and increasing digestion and nutrient absorption.

Both the sympathetic and parasympathetic nervous systems are necessary to maintain homeostasis. We simply couldn’t live without either one of them. However, like all things in life, moderation is key. Over and under-responsive systems can lead to dysfunction, but we'll cover this later.