WHAT IS THE NERVOUS SYSTEM?

August 7, 2025 * Written by Katherine Kraft

Hello and welcome to KMK Coaching! Since my specialty is helping children and families build a healthy and resilient nervous system, I thought first it would be important to understand what the nervous system is all about and why it is the foundation for change and healing from the inside out! So, that is the topic for my first blog - read on:

The nervous system consists of the brain, spinal cord and nerves which work together as a communication network for the body.  It is composed of both the Central Nervous System which includes the brain and spinal cord as well as the Peripheral Nervous System which includes the nerves extending from the CNS throughout the body.  The nerves are bundles of neurons that both carry signals from the brain and spinal cord through the body as well as receive signals from the body to transmit for processing in the brain.  Information that the nerves carry can be either sensory input information which the brain then processes and generates an appropriate response (i.e., hand touches hot object, brain tells hand to move off hot object) or motor output which gives us the ability to move all parts of our body.

How The Nervous System Develops

The first part of the fetus to develop in utero is the neural tube which becomes the brain and spinal cord.  The brain and spinal cord begin forming around the same time as the heart (3rd week of gestation).  Fetal reflexes are present by the end of the first trimester of pregnancy and the senses of hearing, smell and touch are functioning at the end of the second trimester.  The nervous system is developed from another layer of embryonic tissue; then muscles, bones and all the other systems of the body (circulatory, respiratory, urinary, reproductive, digestive and other organs) are developed from other embryonic tissue layers.  The nervous system continues to develop and become more refined throughout the duration of pregnancy and further into early childhood.

Obviously, without our nervous system we would not be able to be the complex human beings we were created to be.  Everything we do – all the senses we take in, process and all of our motor movements – is processed, communicated to the brain, and regulated by our amazing nervous system!

Toxin & Trauma Impact on Nervous System

It is well-known that certain events a pregnant mother experiences or certain toxins/chemicals she is exposed to can cause damage to the central nervous system of the brain and spinal cord.  These can include severe infections (rubella, CMV, toxoplasmosis), nutritional deficiencies especially folic acid, exposure to radiation, medications or illicit drugs and any physical trauma to the baby that occurs during pregnancy or during birth.  But what about the peripheral nervous system, specifically the autonomic nervous system, the one that is responsible for regulating heartbeat, respiration, blood pressure, stress response, etc.?  Can that be “damaged” or negatively affected during pregnancy or birth?  YES absolutely!

 The Autonomic Nervous System (“ANS”) is very susceptible to injury, especially in cases of prematurity or birth complications (dropped heart rate, emergency C section, stuck in the birth canal, lack of oxygen or other fetal distress resulting in NICU hospitalization, etc.).  These situations can lead to an injured ANS and result in issues with not only the physiology of heart rate variability, blood pressure and respiratory rate but can also impact brain development, stress response, mood regulation and overall neurological development.

For a more in-depth discussion of the development of the sympathetic and parasympathetic states of the nervous system during pregnancy, check out this article which also includes a description of the role the vagus nerve plays in the nervous system development: 

“A Review on the Vagus Nerve and ANS During Fetal Development:  Searching for Critical Windows”, Frontiers in Neuroscience, 9/20/21

https://pmc.ncbi.nlm.nih.gov/articles/PMC8488382/

Mother’s Nervous System = Infant’s Nervous System

It is clear that physical incidents, events or situations (toxins, trauma) can harm the fetus and the developing nervous system.  As the above article states, the nervous system can also be adversely affected by chronic emotional stress or trauma.  This can incorporate a multitude of stresses or events in life that impact the mother’s nervous system:  change in job situation, a move, death of a family member, trauma to family member or friend, financial stress, emotional stress from job or family situation, etc.  All of these stresses impact the vagus nerve of the mother’s nervous system.  The vagus nerve (more on that later) is responsible for regulating the nervous system and keeping it in a calm, regulated state.  When a stressful event occurs, a well-regulated nervous system will be able to manage the stress and return to a calm, regulated state through the vagus nerve.  However, if the perceived threat/danger is not able to be addressed, then the vagus nerve will continue to shut down other unnecessary systems (reproduction, digestion, etc) as the focus is solely on survival.  This is why some of us can experience chronic fatigue and burnout – the body’s resources become depleted over time with chronic physical, chemical or emotional stress.

In utero and during infancy, a child is not able to regulate their own nervous system.  They are completely dependent on the nervous system of their mom/caregiver to keep them calm and regulated.  If a pregnant mom is experiencing chronic emotional stress or has a traumatic event that causes her nervous system to have a significant trauma response, the baby’s nervous system in utero will also experience that stress.  Likewise, once born, an infant will reflect the parent’s or caregiver’s nervous system state – whether calm and regulated or stressed and activated.  This is part of how a child’s nervous system is “wired” and shapes their behavior, actions and relationships as they grow into adults.

In the development of the nervous system, there is something called a “window of tolerance.”  This is the determination of how much stress the infant can handle before going into a stress response.  As the infant gets older and becomes a toddler and young child, their tolerance may be noticeably narrow if they become upset easily, are unable to calm down, have extreme mood swings, etc.  – emotional dysregulation  if you will.  Whereas, conversely, in a child with a healthy, resilient nervous system, they may become upset as all infants and toddlers do but are easily calmed down and regulated again – they don’t become stuck in the “upset” stage.  Children can also have a dysregulated nervous system if they tend to withdraw, isolate, not communicate, not show emotion, etc.  All of that is determined by how their nervous system is developed in utero according to the experience of their mother as well as their birth experience.

 We will dive more into the states of the nervous system in the next blog, but for now, I hope this gives you an understanding of what the nervous system is, why it is important, how it can be negatively affected in utero and at birth and what behaviors in children can look like as a result.  All hope is not lost!  The beautiful thing about our brain is that change can happen at ANY age thanks to neuroplasticity – both parents’ and children’s nervous systems have the ability to make change and widen their window of tolerance to improve their ability to handle stress and their emotional dysregulation.  I was able to change mine, so I hope you will join me in this journey as we explore how that can be done!