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Get to know your Autonomic Nervous System: Sympathetic vs Parasympathetic (and how to influence it)

If you’ve ever felt that rush when you have to slam on the brakes while driving, you’ve met your sympathetic nervous system. If you’ve slid into a genuinely restorative nap while sitting in the sun, you’ve met its quieter counterpart, the parasympathetic. These are the two main branches of your autonomic nervous system — the behind-the-scenes circuitry that keeps you alive without you having to think about it. They’re both essential; the magic is in the balance.


Sympathetic (fight/flight/focus)

Think: mobilise, protect, perform. In short bursts, sympathetic activation is brilliant — your pupils widen, heart rate and blood pressure rise, airways open, glucose is released for fast fuel, all of the things that will better enable you to run from a tiger. Digestion, salivation, and longer-term repair step back so you can handle the moment. Great for presentations, sprints, and sudden swerves on the motorway — not great as a permanent address.


Parasympathetic (rest/digest/restore)

Think: soothe, digest, repair. Heart rate slows, blood pressure eases, gut motility and enzyme release rise, saliva returns, pupils constrict, and the body leans into recovery, neural plasticity, and connection. This branch (largely via the vagus nerve) is your happy place for healing, learning, and sleep quality.


Why both matter

Living entirely sympathetic burns you out; living only in parasympathetic leaves you flat and unresponsive. If a tiger is chasing you you really do not want to be in a meditative state. Equally, if you are in no imminent danger you really do need to digest your food, get a good night's sleep and build neural connections for all the new things you have learned in the day. A resilient system switches freely between the two — up when life asks more of you, down when it’s time to digest, repair, and sleep.



Daily life and your total stress load

Modern life layers multiple stressors. None of these are bad in isolation; it’s the stack that counts — what stress scientists call allostatic load (the wear-and-tear of chronic activation).


  • Artificial light after sundown. Evening light (especially from screens) suppresses melatonin and shifts circadian timing, which can fragment sleep and nudge up next-day stress reactivity. Dim the lights and use warmer tones after dusk or buy yourself a pair of blue-light-blocking glasses.

  • 'Food-like' ultra-processed options. Diets high in ultra-processed foods are associated with low-grade inflammation and metabolic stress — both raise the body’s baseline stress trigger, meaning your stress response is more easily triggered. Prioritise minimally processed meals most of the time.

  • Environmental and psychological stressors. Noise, pollutants, workload, financial worries, and micro-stresses all add up. Over time, the body pays a biological price unless we insert regular downshifts to recover.


The takeaway... You don’t have to eliminate stress; you just need reliable ways to complete the stress cycle and tip back into a parasympathetic state.


How to actively engage your parasympathetic system

So, if the autonomic nervous system is controlled without you having to think about it, can you influence which branch you are activating? Absolutely! Below are evidence-informed practices you can try today. Keep it simple: pick one, weave it into an existing routine (after your evening cuppa, post-school run, pre-bed), and let consistency do the heavy lifting.


1) The Physiological Sigh (60–120 seconds)

A rapid, mechanical way to downshift—especially when you feel keyed up.


How to do it

  1. Inhale through the nose.

  2. Without exhaling, take a second, shorter nasal inhale to 'top up' the lungs.

  3. Long, unhurried exhale through the mouth until empty.

  4. Repeat 1–5 times as needed (or do 3–5 minutes as a mini-practice).


Why it works

The double inhale helps reopen tiny air sacs in the lungs (alveoli) that can partially collapse during stress or shallow breathing. Re-inflating them improves gas exchange and naturally lengthens the exhale — signals that cue the parasympathetic system and slow the heart rate. Research also shows exhale-emphasised cyclic sighing can lower breathing rate and improve mood more than generic mindfulness in brief daily bouts.


Tip: Use this before your meals to give your digestive system the best chance of getting the goodness out of your food.


2) Non-Sleep Deep Rest (NSDR) (10–30 minutes)

A guided, eyes-closed protocol designed to place your brain and body into a deeply relaxed, learning-friendly state — excellent for restoring energy after a poor night’s sleep or a demanding day. Try one of Dr Andrew Huberman’s free tracks:



These protocols are essentially modern, science-framed relaxations closely related to Yoga Nidra (below).


How to use: Lie down in a comfortable position, use a blanket to keep warm if you prefer, put your headphones on, press play and let Dr Huberman do the work.


3) Yoga Nidra (15–35 minutes)

A deeply restful, guided body-scan practice from the yogic tradition. It reliably increases parasympathetic tone and can support sleep quality. For a free, reputable sample, explore the Yoga Nidra Network library (many lengths and voices): Yoga Nidrā Network


How to use: Choose a 20–30 minute track in the afternoon or early evening, or as a wind-down before bed.


4) Breath-and-body down-regulation (Jill Miller’s Body by Breath)

Jill Miller blends breathwork, positional release, and gentle rolling to coax the diaphragm and ribcage out of bracing, which can flip you back into parasympathetic. Start with resources here:


Try this simple set-up (5–8 minutes):

  • Lie on your back, calves on a chair, hands on low ribs.

  • 4 seconds nasal inhale, 6–8 seconds gentle exhale; feel ribs move wide, back, down.

  • Optional: place a soft ball or folded towel under the mid-back for feedback (comfort first!). Aim for zero strain, jaw unclenched, eyes soft.

Gentle note: Nothing here is medical advice. If you have a respiratory, cardiovascular, pregnancy-related, or mental-health condition, or you feel worse during any practice, pause and check in with a qualified clinician.


To Wellness!


April

Want to learn more?


Effects of light on human circadian rhythms, sleep and mood (Somnologie)


 
 
 

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