The Social Nervous System

Feeling more connected in the body is at the core of Craniosacral Therapy. When we feel safe with the connections in our body, we feel safer with other people and can have more choice in our relationships. Prof Stephen Porges has described  how the human nervous system has evolved to respond to stress with his ‘Polyvagal Theory & the Social Nervous System‘ model. This understanding of how the nervous system helps to regulate and support social interactions, emotions and sensations underpins much of my clinical work, below is a summary of the main points.

In Polyvagal Theory, Porges discusses some of the evolutionary differences between humans and other animals in adapting to our environment and coping with stressful and threatening situations. For humans, he suggests there is a three-tier hierarchy of responses to stress, I’d like to focus on the first response, Communication or the Social Nervous System:

Porges’ three-tier hierarchy of responses to stress

1. Communication – using negotiation, social skills, vocalisation, listening and facial expression to resolve the stressful situation through social engagement and relationships (Social Nervous System)
2. Mobilisation – fight/flight, energy is mobilised to defend or escape from the threat physically (Sympathetic Nervous System)
3. Immobilisation – freeze response, body systems (digestion, respiration, movement) slow or shut down ie ‘playing dead’ (Parasympathetic Nervous System)

Mammals (especially humans) have developed the ability to use their social networks and skills to find safety from threats in their environment. In humans, this has deepened further with the complex social structures and behaviours that we use to ‘be’ safe and in a more nuanced way, to ‘feel’ safe. In an ideal situation, mammals will use communication and their social group in response to stress or threat, however, if this strategy is unsuccessful mobilisation or resources by fight or flight becomes the ‘next best’ option. If this response is overwhelmed (eg fighting becomes ineffective and/or there is no escape route)  the mammal will immobilise until the threat is gone (as in the freeze response video below). Non-social animals like fish and repitles only have mobilisation and immobilisation responses.

In his model of  the Social Nervous System, Porges describes the neurological features of humans that allow us to respond through social engagement. He highlights the relationships between the Cranial Nerves (CN) of the Autonomic Nervous System (ANS), and includes the CNs in the neck, the throat, the face and the middle ear.

How does the Social Nervous System enable us  to respond to stress?

ANS – (CN X vagus nerve) heart and breathing rates are slowed down while we assess if a situation is threatening. If there is no threat, both rates return to ‘normal’. If there is a threat, the heart and breathing rates are fine-tuned to enable a social  response (see throat, face, ears section), as we need different ways of breathing for speaking than for running, fighting or playing dead. To enable a more flexible response to stress, humans have an extra cluster of nerve tissue in the brain stem where the sensory nerves from the heart feedback to, called the nucleus ambiguus, unlike non-social animals like fish and reptiles who only have the dorsal motor nucleus.

Neck – (CN XI accessory nerve) the trapezius and sternomastoid muscles are activated, enabling us to turn our heads to orient towards a potential threat and also to members of our group to engage socially (see below).

Throat, Face & Ears – (CN V trigeminal, VII facial & IX glossopharyngeal nerves) In the throat, swallowing and vocal prosody are adjusted so that we can give a specific vocal response to stress, eg a rousing scream or a soothing whisper. Muscles of the face and jaw help with the articulation and pronunciation of words as well as facial expression, the movement of the muscles around the eyes are particularly important in social engagement and communication. One of the most interesting connections that Porges has made is the passage of the facial nerve through the muscles of the middle ear which enable us to attune to sounds so that we can distinguish the human voice from background noise. Facial expression is hard-wired into the recognition of the human voice.

The Social Nervous System helps us to appreciate the heart, digestive organs, face, voice and ears as a unified system which can be affected by a vast array of factors including stress, shock & trauma, ear issues, surgery, digestive issues, dental work and developmental conditions. Mobilisation and immobilisation are vital responses for survival and are to be appreciated. Social engagement enables us to move beyond survival to being able to thrive in our lives and relationships. As a Craniosacral Practitioner, the Social Nervous System helps me understand the importance of feeling safe and finding support in human connection and social engagement. I’m privileged to see the sense of health and wellbeing growing in my clients when stimulating these amazing neurological mechanisms through touch and communication in our sessions. As this happens, there is a greater capacity and flexibility to move between all three responses.