We love talking about muscles and fat when discussing our fitness goals.
We tend to focus on well-known organs like the heart and lungs when working to improve our health.
One system that doesn’t get nearly the love it deserves is the nervous system.
In this article, we’ll briefly cover some main points about the nervous system and explore an example of how your nervous system interacts with the rest of your body.
The nervous system is a network of nerve cells called “neurons” that controls how our bodies interact with the environment and maintain internal homeostasis (keep us alive).
The two primary parts of the nervous system are the central nervous system, comprising the brain and spinal cord, and the peripheral nervous system, the remaining nerves throughout the body.
“Afferent” neurons bring information from the body back to the central nervous system while “efferent” neurons carry signals from the central nervous system out to the body.
These neurons communicate with organs, muscles, and glands through chemical neurotransmitters and electrical signals.
The peripheral nervous system has a “somatic” component and an “autonomic” component.
The somatic component of the peripheral nervous system controls the organs and tissues involved in the actions and behaviors that we engage in consciously and voluntarily (e.g. muscles and skin).
The autonomic component of the peripheral nervous system controls all of the internal processes – breathing, swallowing, digestion, heart rate, and hormonal secretion – involved in maintaining homeostasis.
The autonomic nervous system has three branches:
The sympathetic branch of the autonomic nervous system is often referred to as the “fight or flight” component, as it prepares us for action and halts “non-essential” functions in the face of a threat.
The sympathetic branch initiates increased heart rate, pupil dilation, perspiration, relaxation of veins and arteries, liver glucose production, and fatty acid mobilization, while inhibiting digestion and suppressing immune function.
The parasympathetic branch works reciprocally to the sympathetic branch and is often referred to as the “rest and digest” component.
The parasympathetic branch slows heart rate, constricts the pupils, initiates liver glycogen synthesis, promotes digestion, activates the immune system, and promotes sexual arousal.
The enteric nervous system communicates with the central nervous system through the vagus and pelvic nerves, but largely operates independently to control digestive tract motility.
Now that we’ve covered the basics, let’s pull this all together in a practical example.
Imagine you just smashed a plate of barbecue, sweet potato fries, and roasted brussels sprouts.
You’re propped up under a tree, completely relaxed, so there’s not a whole lot of somatic peripheral nervous system action.
Your autonomic nervous system is primarily in a parasympathetic state and your enteric nervous system is doing its thing to help keep your meal moving along.
Your heart rate is low, you’re digesting your food, replenishing glycogen stores, and you’re generally enjoying life.
You notice in the distance a police officer pulling up to your car and realize that you didn’t pay the meter when you parked.
Your eyes pick up the light reflecting off of the officer and transmit that signal to your central nervous system, which filters shapes and colors to confirm that you are, indeed, about to get a ticket.
Your central nervous system then kicks your peripheral system into high gear.
Neurons start firing, sending and receiving signals between your central nervous system and your body so that you stand up and start sprinting towards your car (this is somatic).
As your energy demands skyrocket, your autonomic nervous system dials down its parasympathetic activity and dials up its sympathetic action to halt digesting your meal, release stored glucose from your liver, increase your heart rate, open your blood vessels, and sharpen your senses.
You start to sweat because you’ve been slacking in the gym and it’s hot AF outside.
Throughout this entire process, your central nervous system and peripheral nervous system are processing information from your body and your surroundings – position, speed, direction, balance – to guide you towards your car.
When you get to your car, out of breath and breathing heavily, you explain to the officer that you forgot to pay and proceed to put some money in the meter.
The officer is having a pretty good day and decides to leave without writing you a ticket.
With the whole ordeal coming to an end, your autonomic nervous system shifts back towards parasympathetic activity, so your breath slows, your muscles relax, your heart rate decreases, and you stop sweating.
You return to your tree and get back to enjoying your afternoon.
The nervous system is complex, but hopefully this helps clarify some of its major components and activities.
We’ll be referring back to this article in the future as we explore other ways the nervous system is involved in your efforts to look and feel awesome.
Until then, have a most excellent day!
Buchanan TW, Tranel D. Central and peripheral nervous system interactions: from mind to brain to body. Int J Psychophysiol. 2009;72(1):1–4. doi:10.1016/j.ijpsycho.2008.09.002
Catala, M., & Kubis, N. (2013). Gross anatomy and development of the peripheral nervous system. Peripheral Nerve Disorders, 29–41. doi:10.1016/b978-0-444-52902-2.00003-5
Furness J.B., Callaghan B.P., Rivera L.R., Cho HJ. (2014) The Enteric Nervous System and Gastrointestinal Innervation: Integrated Local and Central Control. In: Lyte M., Cryan J. (eds) Microbial Endocrinology: The Microbiota-Gut-Brain Axis in Health and Disease. Advances in Experimental Medicine and Biology, vol 817. Springer, New York, NY
InformedHealth.org [Internet]. Cologne, Germany: Institute for Quality and Efficiency in Health Care (IQWiG); 2006-. How does the nervous system work? 2009 Oct 28 [Updated 2016 Aug 19]. Available from: https://www.ncbi.nlm.nih.gov/books/NBK279390/
LeBouef T, Whited L. Physiology, Autonomic Nervous System. [Updated 2019 Feb 12]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2019 Jan-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK538516/