Our autonomic nervous system runs all our organs and systems, automatically: that’s why its name is derived from the word autonomous. It does this based on feedback from our organ systems, and in response to what’s going on in our environment.
It’s pretty amazing: our temperature, blood pressure and other vital systems are kept within healthy parameters, with no conscious effort or even thought on our parts. When our brain perceives danger in our environment, it revs us up to be able to respond fast, and to take action. Once we are safe, a whole different part of the autonomic nervous system kicks in.
The part that revs us up is called the sympathetic nervous system (SNS).
The part that comes into play when we are safe and relaxed is called the parasympathetic nervous system (PSNS).
The classic short mnemonic for their actions is:
SNS: Fight or flight
PSNS: Rest and digest
And you can’t be in both at the same time!
The Sympathetic Nervous System
We have all heard of the “fight or flight” state, when we are scared or threatened. Our adrenal glands respond by pumping out adrenaline to help us react and move faster. In extreme danger people have even been known to exhibit super-human strength, and time may seem to slow down.
So our age-old survival instinct is to lash out or run away from danger, but neither of those is acceptable in polite company, or at work. We have to "bite our tongues", and instead of working off that adrenaline rush by turning it into physical activity, we are left sitting at our desks, swallowing our stressors, and maybe even feeling shaky from all the circulating adrenaline.
In the fight or flight response, our bodies prioritise sending blood to the muscles, by increasing the how hard and fast our heart pumps and tightening blood vessels to increase blood pressure. The lungs assist by taking in more oxygen. We divert blood from systems that aren’t important for immediate survival, including the digestive system. After all, there’s no point putting energy into digesting, when it is more important to escape!
That stress response is meant to be short term, to help us get out of the stressful situation, so that we can then de-stress and get on with the rest of our lives in a calm manner.
But the mnemonic isn’t complete: It’s not just fight or flight, it is fight or flight, or freeze or please.
For some people, being scared or threatened triggers immobilisation, while others put effort into pleasing the person who is the source of the stress. Those may be more common in children, but behaviours learned in childhood continue to play out in us as adults.
And not all stress is bad! Eustress (healthy stress) includes the stress around happy events such as starting a new job, getting married, or moving house.
The Parasympathetic Nervous System, on the other hand, increases gut motility and the release of digestive secretions. It prioritises blood flow to the digestive organs, and it also causes blood vessels to relax, allowing more blood to carry more nutrients.
This is why you may have heard the advice to not eat when you are highly stressed: because your digestive system isn’t working as well when you are stressed as when you in the calmer parasympathetic state.
This rest and digest state is the state in which the vagus nerve can work, because the vagus nerve is part of the PSNS. This makes sense when you think how much the vagus nerve helps with digestion.
Parasympathetic is the state in which we can heal
Historically if we ran away successfully, then we could relax, feed ourselves, and heal any wounds we had incurred in our fight and our flight.
It’s all about balance. The SNS helps us get things done, the PSNS helps us rest and recuperate. We function best when we can flip into SNS when needed, then relax into PSNS.
But the modern world doesn’t always make that balance easy to achieve. The stressors we encounter in everyday life can trigger our SNS over and over. Having a strip torn off you by your boss, being cut-off in traffic, being unavoidably late for an appointment, working in a noisy crowded environment, worrying about your child coming home late: so many different stressors can mount up through the day, without the opportunity to calm down between them. The result is that many people spend much of their time with their sympathetic nervous system activated.
You can see why it is so useful to learn ways to help yourself move from SNS to PSNS. Here are some suggestions to help with that:
Dance or exercise off your adrenaline at the end of the day
Practice meditation or yoga
Try the vagus nerve reset exercise
Take a hot bath with an enjoyable book and candles
Walk in the woods, or lie out on the grass for 10-15 mins
Pet your dog or cat
Get a massage, or exchange back rubs with your partner
Take deep breaths with a focus on longer (gentle) outbreaths
Why is breathwork helpful?
Our breathing rate is generally set by our autonomic nervous system, automatically. But this is one system that we can also consciously control. This enables us to hack into the feedback loop, changing the message to our CNS. Slowing our breathing can thus help us move into a calmer state.
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