The Science of Fainting

Do you know what happens in your body when you faint?

Photo by Mario Heller on Unsplash


You might have never passed out before but it’s highly likely you have seen or heard of someone who has. Research actually shows that ‘about one-third of people admit to have fainted at least once in their lives’. Roughly one out of three people have fainted. I have, I even wrote about what it felt like (and of course, that’s the inspiration for this post!).

Fainting is that common? Huh! What actually goes on in the body to result in blacking out?

The main gist

Turns out we faint when the brain does not get enough oxygen. Think of it as the brain gasping for air (oxygen) and then shuts down as a defense mechanism.

Entering the medical world…

The medical term for fainting is actually ‘syncope’. Makes sense given that ‘syncope’ is derived from Greek word ‘synkope’ which means ‘cutting off’ or ‘contraction’. We faint when the brain is short of oxygen, and because oxygen comes through the blood, we faint when the brain receives a reduced blood flow.

We can be out for minutes or seconds (Here’s to folks who argue that ‘it’s a lie’ because one passed out for too short a time). Now there are several reasons why blood flow to the brain can reduce; a person might not be medically fit, and a person might be healthy and still faint (75% of people fall here).

Ok, what then are the types of fainting?

Remember there are several reasons a person can faint? Well, they can be grouped into three:

  • Vasovagal syncope
  • Carotid sinus syncope
  • Situational syncope

Vasovagal syncope

This type has to do with the vagus nerve. The vagus nerve is a brain nerve responsible for sensations we feel on our skin, in our muscles and in our organs [p.s: sensation = a physical feeling resulting from something happening (in our nerves), cred to Google].

So, if the vagus nerve overreacts, it will reduce our heart rate and reduce the amount of blood the brain receives (there’s your gasping brain).

But when will the vagus nerve overreact? Due to the nature of its function, the vagus nerve can overreact when we’re stressed emotionally or physically (explains why I fainted out of hunger), when we see blood, or when we stand for long. We can also make our vagus nerve overreact when we strain ourselves using the loo (lol, explains why some faint taking a shit) or when we cough with so much vigour.

Solution: Don’t stress yourself guys, take it easy! And don’t skip meals!

Carotid sinus syncope

This type happens when we constrict the carotid artery. The carotid artery is located in the neck and supplies blood to the brain. So, we can faint if we turn our heads sideways too much or wear something too tight at the neck.

Solution: Don’t voluntarily choke.

Abnormal Heart Rhythms

Outside the 75%, if your heart is known to be faster or slower than normal, your blood pressure is bound to drop and then, gasping brain effect. In other words, you faint. Typically, abnormal heart rhythms result from heart diseases, some medications, or an overactive thyroid gland.

Solution: Go see a doctor!

Zoom out…

So, there you have it: why we could faint and what goes on in the body to result in fainting. Fascinating, right?

If you want to read more on the fainting biz, like the tell tale signs you’re about to faint, you can start from my references:

What Causes Fainting?

What happens when you faint? — Harvard Health

Vagus Nerve: Function, Stimulation, and More

Internal Carotid Artery Anatomy, Function & Diagram | Body Maps

Overactive thyroid (hyperthyroidism) — Symptoms


I am not an authority on this topic and researched credible sources to produce this write-up. There is a lightheartedness to this post. On that note, if you do faint, and you do understand your medical history, you’d know whether your loss of consciousness was due to certain actions you took or whether it’s a symptom of an underlying ailment, in which case, you need to see a doctor. But by all means, go see a doctor, panic-warranting or not. Better safe than sorry.

Stay healthy folks!

From Dayo



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