The Autonomic Nervous System Explained

Autonomic Nervous System: The autonomic nervous system regulates bodily functions and is largely unconscious/involuntary. It is regulated by the Hypothalamus. It is made up of three sections: Sympathetic and Parasympathetic and Enteric (which is confined to the gut). We will focus on the first two.

Sympathetic Nervous System: Accelerates heart rate, constricts blood vessels and raise blood pressure.

Parasympathetic nervous system: Slows heart rate, increased intestinal activity, relaxes muscles These both work together to regulate..

Polyvagal Theory: Stephen Porges developed Polyvagal theory, which explains the physiological aspect of social engagement - in terms, safety and danger. Here are some key terms and explanations:

Vagus Nerve: Also known as the tenth cranial nerve, the vagus nerve travels from the brain stem, and supplies nerve fibers to the pharynx (throat), larynx (voice box), trachea (windpipe), lungs, heart, esophagus, and intestinal tract, as far as the transverse portion of the colon. The vagus nerve also brings sensory information back to the brain from the ear, tongue, pharynx, and larynx.

Ventral Vagal: When our system experiences safety and regulation in the external environment, we operate in ventral vagal. It is also known as ‘rest and digest’. In this mode, we are safe and well. The body is able to send resources where, needed. We are also better able to respond rather than react here. It is also the place where can most easily connect with both ourselves and others. This is the place of social engagement.

Sympathetic Activation: When an external stimulus interacts with our nervous system, it starts to respond or ‘activate’. There is a level of alertness that builds within our system. We need to go into sympathetic activation daily – to do our work, exercise and socially interact. A healthy nervous system will move easily between ventral vagal and sympathetic activation.

Fight or Flight Response: When there is too much external stimuli or stress, sympathetic activation turns into a danger response ‘fight or flight’.  The body experiences danger/threat and kicks into survival mode. In fight or flight mode, our body sends resources to the places that are in danger. And it may deplete resources from other areas. It is trying to survive. In primitive times, fight or flight would be a response to presumed danger or death. In today’s society it is a trauma and stress response. Many of us live in a permanent state of fight or flight.

Dorsal Vagal Response: When the level of threat becomes too high, the nervous system activates the dorsal vagal response like a hard brake. It is also known as shut down or freeze response. The nervous system says ‘No. I cannot take anymore stimulation.’ Symptoms of dorsal vagal response vary and may include: collapse/fainting, emotional shut down or dissociation, inability to speak or move certain parts of the body.