What is the Vagus Nerve?

Vagus means wanderer. I thought that appropriate, since as trauma survivors it can feel like we're wandering this earth a bit aimlessly.

The vagus nerve is the main component of the parasympathetic nervous system. The parasympathetic nervous system is the spinal nerve system that helps regulate heart and breath rhythms. But let's get back to the vagus.

The vagus is the 10th cranial nerve and the longest nerve in the body. The vagus nerve extends from the brainstem down into the muscles of the face, inner ear, throat, heart, lungs, stomach, and intestines. What's really fascinating is the vagal pathways are bidirectional, 80% of the information is traveling from the body to the brain. The vagus is divided into two parts. The ventral vagus and the dorsal vagus. In daily function, the ventral helps create homeostasis and the dorsal brings healthy digestion.

But what does all that have to do with trauma? According to Dr. Stephen Porge’s Polyvagal Theory, the autonomic nervous system comprises a three-part hierarchical structure: the dorsal vagal system, the sympathetic nervous system, and the ventral vagal system. The dorsal vagal system, which is the oldest of the systems, immobilizes the body in response to life threatening situations by facilitating a shut down response. The sympathetic nervous system, which is comparatively newer to evolve, mobilizes the body in response to threat by activating the fight-or-flight response. The ventral vagal system, which is the newest and most evolved of the structures, this “social engagement” system is the branch of the parasympathetic nervous system that helps you relax and connect to others when you feel safe.

When activated or stimulated out of normal daily function into a threat response, all kinds of things happen in the body. The breath changes, the body constricts, the heart rate increases, digestion slows, more sugar is created, pupils dilate, skin may become pale or flushed.

Think about the animal kingdom, predator and prey scenarios. When animals experience threats, their bodies release the hormone adrenaline/epinephrine which would lead to a series of bodily changes including increased heart rate and respiration. This response helps them flee or fight. In other cases, an animal will freeze which involves breathing shallowly or holding the breath in order to avoid being sensed by a predator. This freeze reaction leads the animal to stand very still which is an immobilization response to threat. Some animals will faint so that a predator who is not a scavenger might lose interest in a dead animal. Both the freeze and faint responses are facilitated by an evolutionarily older pathway of the vagus nerve and part of the parasympathetic nervous system.

Once safe, an animal will release the stress response through shaking and breathing in a way that restores regulation. However, we humans will often stay in both fight and flight or freeze and faint responses for extended periods of time. This tends to be the case when trauma is chronic and repeated, as in the case of Complex PTSD. Additionally, we often do not have sufficient opportunities to process stressful or traumatic events. This can lead to physical tension, chronic pain, restricted breathing patterns, digestion problems, and hypersensitivities to noise, just to name a few.

Understanding the body's natural responses of flight, fight, freeze, and faint can help you become more aware of your own cues of threat/stress. Then you can learn strategies that help you restore a sense of safety and explore ways to react differently.

Ah, the wonder of the wandering nerve. Keep wondering and wandering.