What is the nervous system? by Dr. Hailey Jackson

ByTaylor Nye

PublishedJuly 28, 2023

What is the nervous system?

The nervous system includes the brain, spinal cord, and nerves that course from the spinal cord to the muscles. Basically, it’s the electricity in the human body that allows our muscles to move. Additionally, it allows for digestion, plays a role in cardiac function, respiration, and plays a major role in one’s ability to rest. Within the nervous system are the autonomic nervous system (this works automatically) and the somatic nervous system (this works volitionally).

What is the sympathetic nervous system?

The sympathetic nervous nervous system is a branch of the autonomic nervous system.

It is responsible for the fight, flight, freeze, and/or fawn response. Fibers from the SNS innervate almost every organ system.

What is the parasympathetic nervous system?

The parasympathetic nervous system is responsible for resting and digesting (includes defecation & urination). The vagus nerve is the primary nerve of the PNS, as it carries 75% of all parasympathetic fibers. Most people have an underactive parasympathetic nervous system and an overactive sympathetic nervous system.

What happens at the organ level when the sympathetic nervous system is activated?

The sympathetic nervous system should be preparing the body for physical activity by affecting many organ systems to redirect oxygen rich blood to the areas of the body that need it during said activity. We are wired for survival!

What causes the sympathetic nervous system to be activated?

The SNS responds to neural or hormonal responses to stress (increases in corticotropin & cortisol). When it is activated, heart rate increases, lung passageways expand, the large intestine motility decreases, blood vessels constrict, pupils dilate, and blood pressure is elevated among other things.

What are the long term adverse effects of a chronically overactive sympathetic nervous system?

Chronic stress can result in long-term stimulation of the fight or flight response, which leads to consistent production and secretion of catecholamines and hormones like cortisol. Long term production of these substances can lead to high blood glucose levels, which can in turn lead to type 2 diabetes and hypertension, which can lead to cardiovascular disease.

What can you do about it?

My favorite recommendation for sympathetic nervous system over activation is breathing exercises. One of my favorite breathing exercises is box breathing. Try inhaling for 4 seconds, hold for 4 seconds, exhale for 4 seconds, and hold for 4 seconds. This is challenging at first, so repeat as many times as you comfortably can. By altering the way you breathe, you send safety signals to your nervous system essentially telling it to chill out. The cool thing about it is, by changing the way you breathe, you can alter the nervous system, which then affects several systems. Afterall, the nervous system is the queen bee!