Yoga and the Nervous System: Why a Slow Practice Settles You

Everybody who has finished a long savasana knows the feeling of getting up as a slightly different person than the one who lay down. The vocabulary for what happened there comes from the nervous system, and it is the part of anatomy that explains most about why yoga does what it does.

This is the fourth post in our anatomy series. It covers the structure a training course teaches — central and peripheral, somatic and autonomic, sympathetic and parasympathetic — and what each part has to do with a class.

One boundary first, and it is firmer in this post than in any other in the series. A yoga teacher understanding the autonomic nervous system is not a yoga teacher qualified to treat anxiety, trauma or any diagnosed condition. This is anatomy for teaching. Anybody managing a condition should be talking to their doctor, and a teacher's job is to make the room safe for them rather than to treat them.

What the nervous system is

The nervous system is the body's main controlling and coordinating system. It regulates every activity, voluntary and involuntary, and adjusts you to your surroundings. It does that on three properties: sensitivity (it registers what is happening), conductivity (it carries the signal), and responsiveness (it acts on it).

That is worth reading twice, because it is also a fair description of what a practice trains. Noticing a sensation, letting the information travel, responding rather than reacting.

The two main divisions

Central nervous system (CNS)

The brain and the spinal cord. It controls the body's biological processes and all conscious thought, and because of that importance both parts are encased in bone — the cranium around the brain, the spine around the cord.

Two regions of the brain come up in a yoga context. The brainstem is the connection between the rest of the brain and the central nervous system, and it is primarily concerned with life support: cardiovascular control, respiratory control, pain sensitivity, alertness, awareness and consciousness. The cerebral cortex handles the higher functions — it is what takes the flood of incoming information from the peripheral nerves and turns it into something you can actually feel and think about.

That the brainstem handles both breath and alertness, in the same small structure, is not a coincidence a yoga tradition would find surprising.

Peripheral nervous system (PNS)

Everything else — every part of the nervous system that is not the brain or the spinal cord. A nerve is a bundle of peripheral axons wrapped in connective tissue, carrying signals out to the body and back again.

The spinal cord is the main pathway connecting the brain to all of it. It is considerably shorter than the bony column that houses it, which is one of those facts that stops a student assuming the cord runs the full length of the back.

The peripheral system divides again, into two.

Somatic and autonomic: the voluntary and the involuntary

The somatic nervous system is responsible for the voluntary movement of the body — movement you consciously thought about doing. Lifting an arm into the first position of a sun salutation is somatic.

The autonomic nervous system controls the unconscious functions: sweating, salivation, the peristalsis that moves food along the digestive tract. Nobody decides to do any of it.

The breath is the interesting case, and it is the reason pranayama exists as a subject at all. Breathing happens perfectly well without attention — and it is also the one autonomic function you can take deliberate hold of whenever you choose. It is the doorway between the two systems, and every breathing practice in a syllabus is working that doorway.

Sympathetic and parasympathetic: the pair that matters most

The autonomic system is made of two coordinating systems that adjust automatically to the environment.

Sympathetic. Its activities are widespread and diffuse, and they exist to meet acute emergencies. This is the branch that mobilizes the body's resources under stress — the fight-or-flight response. It spends.

Parasympathetic. Its activities are discrete and isolated, and they provide a comfortable environment. It is responsible for stimulating the activities that occur when the body is at rest, and its main goal is to conserve the body's resources so that they last longer. It restores.

Both are necessary. The sympathetic branch is not a malfunction — it is what gets you out of the road. The difficulty is one of proportion: the stress of modern life keeps the sympathetic system activated by conscious and unconscious stimuli far more of the time than a body is built for, and the parasympathetic side gets very little room.

What a slow practice, a long exhale and an unhurried savasana are doing is giving it that room. Not fixing anything, not treating anything — providing the conditions for rest that a normal day does not.

What follows for the way a class is built

Once you understand the pair, several things that look like tradition turn out to have structure behind them.

• Savasana is not the optional part. It is the part of the class the restoring branch actually gets. A class that runs long and drops it has taken out the one section that was doing that job.
• The exhale is the settling half of the breath. It is why slow, even breathing appears in every tradition's instructions for calming down, and why a practice like Nadi Shodhana is taught slowly rather than forcefully.
• Pace is a teaching decision, not a style preference. A fast, hot, loud class and a slow, quiet one are asking two different branches of the same system to work. Both are legitimate; teaching only one to everybody is not.
• The end of the class is where the day is decided. Students carry out whatever state the last ten minutes left them in.

And a practical one for teachers: your own nervous system is in the room too. A teacher who arrives rushed and talks fast teaches a fast class regardless of what the sequence says.

Where meditation and Yoga Nidra fit

The practices aimed most directly at this system are the ones where the body stops moving entirely. Meditation, guided relaxation and Yoga Nidra — lying still, awake, while a teacher walks the attention through the body — are all working on the restoring side of the pair rather than the mobilizing one.

That is also why they are so often the practices a tired student resists and then benefits from most. Doing less is not intuitive when you are already depleted.

Studying this properly

The nervous system is the system where reading and experiencing are furthest apart. You can learn the two branches in an afternoon. Recognizing, in a room of fifteen people, which ones are still braced and which have actually let go — and knowing what to change about the next ten minutes because of it — is a different skill.

On our 200 hour yoga teacher training in Rishikesh, anatomy and physiology runs as a daily class over 27 days, alongside pranayama, meditation and Yoga Nidra — so the theory of this system and the practices aimed at it are taught in the same week rather than in different years.

Next in the series

The somatic nervous system moves the body by way of muscles, which is the next post: the muscular system in yoga. The cord running through the column is covered in spine anatomy for yoga, and the overview of all seven systems is yoga anatomy for teachers.