Nervous System Basics: Part I
article at a glance:
Basics of the autonomic nervous system and how it applies to stress, emotions, & behavior
Polyvagal Theory and brief review of the Vagus Nerve
The 3 main nervous system responses
A resilient nervous system
The Autonomic Nervous System
The autonomic nervous system operates involuntarily, and regulates many of our primary bodily functions including heart rate, breathing, blood flow, digestion, pupillary response, and sexual arousal. Its also the system that initiates and controls the fight, flight, and freeze response. This system plays an important role in our physical and mental wellbeing, and it operates beneath our conscious awareness for the most part.
Polyvagal Theory
For a long time the body has been left out of the mental health conversation and now we are just catching up. The nervous system plays an important role in creating wellbeing AND let’s also keep in mind, it’s not the only thing to consider in a healing process.
In my somatic and trauma resolution training, one of the core pillars we work from is the Polyvagal Theory (which I will occasionally refer to as ‘PVT’). Polyvagal Theory was developed by Dr. Stephen Porges and gives us a general understanding of how the autonomic nervous system functions. ‘Poly’ meaning many, and ‘vagal’ referring to the vagus nerve.
a foundation for understanding for stress, emotion, behavior and trauma
While PVT is useful to create a foundation of understanding, its also important to emphasize that PVT does not explain all of the complexities and nuances of the soma and the psyche. I do find that as I work with clients, its helpful to have a basic understanding of the nervous system and PVT to give us a framework to pull from.
*In future journal posts, I will also discuss the misconceptions of PVT and how gripping to a linear model may prevent us from true growth and transformation.
The Vagus Nerve
The ‘walkie-talkie’ system between brain & body
The Vagus Nerve is a key player in the autonomic nervous system responses, and how the body enters into different physiological states.
Vagus means ‘wanderer’ in Latin and the Vagus Nerve wanders throughout the body. It starts from the brain and runs through the face, throat, heart and all the way to the viscera in the abdomen.
It is one of the main highways of communication from brain to body. 80% of the vagus nerve’s function is to send information from the body, up to the brain. Some refer to the vagus nerve as a ‘walkie-talkie’ system between the brain & body.
The Vagal Break
The Vagal Brake is what helps to increase and decrease heart rate and helps us to move between mobilization & rest.
The Sympathetic Cardiac nerves help to increase the heart rate to mobilize the body into a Sympathetic state (i.e. pressing on the gas pedal)
The Vagus Nerve helps to decrease heart rate, and help the body enter into Parasympathetic state (i.e. pressing on the brake pedal)
Neuroception & Nervous System States
Dr. Porges describes neuroception as ‘detection without awareness’. Throughout our day, we take in information from our external environment, people around us, and also internally. As we take in this information, the body & brain work together to determine what is safe or unsafe.
Depending on what the body & nervous system detect through neuroception, we enter into a one (or a blend) of the following physiological states in the autonomic nervous system:
Sympathetic (mobilize)
Parasympathetic: Ventral Vagal (social engagement)
Parasympathetic: Dorsal Vagal (stillness or immobilize)
Each of these branches of the nervous system serves a unique purpose and plays a role in our stress response as mammals.
Sympathetic Nervous System
The Gas Pedal
Imagine the Sympathetic nervous system as the gas pedal in the body. It speeds the body up and mobilizes the body for action!
Sensory input activates the hypothalamus, and triggers hormonal, chemical, and biological responses that prepare a person for activity or for response to stress/threat.
The Sympathetic Nervous System can be activated in
MOVE & PLAY: When we are generally safe or at ease the body can mobilize in play, exercise, sexual activity, healthy aggression, focusing on a task, and even simple tasks like getting up out of bed in the morning.
FIGHT & FLIGHT: When we are in a stress or threat response the body mobilizes into fight, argue, flight, or avoid to protect us from whatever stress we are facing.
What happens physiologically in the body
Activates the HPA Axis & adrenal response
Increases heart rate, respiration, and blood pressure
Blood shifts away from digestive system and moves to our muscles to allow for quicker movement
Constriction of blood vessels, pulling blood away from periphery
Pupils dilate
Muscle tone intensifies
Increased sweating
Parasympathetic Nervous System
The Brake Pedal
Imagine the parasympathetic nervous system as the brake pedal, it slows the body down and is an energy conserving system.
There are 2 branches of the Parasympathetic Nervous System: The Ventral Vagal (Social Nervous System) & Dorsal Vagal States.
We are built to operate in our parasympathetic nervous system for most of our day.
What happens physiologically in the body:
Heart rate slows and blood pressure lowers
Blood is directed to the digestive organs to aid in digestion
Helps us to let go of muscle tension
Breathing slows and deepens
Immune system can fully function
The 2 Branches of the Parasympathetic Nervous System
The Vagus Nerve plays a significant role in the Parasympathetic Nervous System and there are two distinctive branches.
Ventral Vagal / The “Social Nervous System”
This part of the vagus nerve runs above the diaphragm and alongside the front of the body. It connects to the face, pharynx and larynx, heart, and lungs.
SOCIAL ENGAGEMENT: When we feel generally safe the social nervous system is online. It supports our ability to socially engage, bond with others, communicate, be intimate with others, and problem solve together.
FIT IN / FAWN RESPONSE: Under stress or threat the social nervous system may fall into patterns of fitting in, fawning, people pleasing, appeasing, etc. We may also experience things like imposter syndrome, isolation, and loneliness. These patterns are beautiful survival strategies and are dependent on our life experiences, attachment styles, and possibly what was modeled to us as children.
2. Dorsal Vagal
This part of the vagus nerve runs below the diaphragm and along the back of the body, connecting to the stomach, liver, spleen, kidney, colon, and intestines.
REST & DIGEST: In a safe, easeful resting state, Dorsal Vagal is responsible for rest, digestion, recovery, and healing.
FREEZE & IMMOBILITY: When we perceive or detect we are under life threat, Dorsal Vagal can take over and it slams on the break. Collapse occurs and the gut shuts down to support our freeze and immobility response. In a freeze response we may also experience resignation, procrastination, helplessness, apathy, numbness, confusion, or disorientation.
A Note on Trauma and the Nervous System
In trauma, the competing energies of mobilizing can overwhelm the nervous system which causes the body to enter the shutdown freeze response (also referred to as tonic immobility or paralysis). The freeze response creates a feeling of ‘stuck’ within the nervous system, which can also impact emotions, thought narratives, and behaviors (read more about trauma and Polyvagal theory).
A Resilient Nervous System
A resilient nervous system has cycles of sympathetic charge & parasympathetic discharge throughout the day! If a person can feel both activation and settling throughout their day without getting ‘stuck’ in any state, this is an indicator of a supported and resilient nervous system, and an expanded Window of Capacity.
Read more about the Window of Capacity and how SomaWell can help you create a resilient and supported nervous system in Nervous System Basics: Part II.