You don't need to to be an expert about one single nerve in your body, to continue being a good teacher or to make the most of your movement practice.
However, If your social media feed is anything like mine, you can be left with a sense of insufficiency about your anatomical knowledge. I'm here to encourage you to stop scrolling and consider what you know already and how it may well be enough to serve you and your students well. Here are a few practical insights that I have found helpful
1. THE LONG AND WINDING RIVER
You probably know the headline (no pun) information about the vagus: it’s the number 10 of 12 cranial nerves. and it meanders like a river, flowing from your brainstem. One tributary branches into the region of your heart and lungs, another finds its way through your diaphragm to wander the abdominal organs. It also branches towards various facial nerves. If you've come across something called Polyvagal Theory (ref Dr Stephen Porges), you'll know something of the Social Engagement System that can regulate our sympathetic and parasympathetic responses to stress and establishing safety.
The etymology of "vagus" is the Latin vagus meaning things like roaming, wandering, straying (it can also have the sense of vague, uncertain, unspecific). We see it in English in words like vagrant and vagabond.
It is a major player in your parasympathetic system (the rest & digest one) which is the sibling to your sympathetic system (the fight or flight one). I like to call them the Perfect Twins. These systems come under the umbrella term: autonomic, as the processes are largely being orchestrated unconsciously (and reflexively) - you don't need to think about breathing, or digesting, or the hundreds of things your liver does. Thankfully, the systems have their own intelligence, as it were.
3. BALANCE & TONE
If you have a balanced practice of activiity and rest (being wakeful and busy, and able to relax, able to sleep) then you don’t need to “stimulate” the vagus nerve - your systems will work this out for themselves. When these systems are functioning well for us, when we are able to up- and down-regulate without effort, the term you will hear is Autonomic Tone.
4. OUT OF BALANCE?
If, however, you are feeling out of balance (can't rest or relax, fairly tense or stressed most of the time), then the parasympathetic systems states are not so accessible or seem depleted. The simplest (and yet, not always easiest) thing to do is engage in something that makes you happy, makes you smile on the inside (or half smile on the outside). Friends are good, stepping into nature also, and pets can be great.
5. HOW YOUR YOGA PRACTICE HELP
If you really want to “stimulate” your vagus nerve through yoga i.e. let your parasympathetic come forward in your practice, then you have all these techniques and more already in your toolbox:
max out your time in Savasana, maybe shift the balance so your practice is more stillness than movement
do a Restorative practice, like putting your Legs up the Wall or supported on a chair and props (as in Waterfall), for 15 minutes or so
create a playlist of calming music or steady chanting
listen to a guided Yoganidra practice and don't worry if you fall asleep (maybe set a timer before you settle)
practice Brahmari PY (humming bee breath): the vagus passes close to your larynx, the humming creates a soothing vibration close by
encourage your exhalation to lengthen, a very light 'ujjayi' contraction can delicately extend it - go little by little.
And on a final note, the wisdom of the innate balance of the autonomic systems is articulated in the philosophy of asana: the sthira sukham asanam (YSOP 2:46). The essence perhaps of any asana is a process of embodiment that allows the duality of the systems to find their own harmony - and I'm pretty sure Patanjali was not a neuroscientist.