In the BBC radio series, The Curious Cases of Rutherford and Fry, the presenters have been on hand to solve everyday mysteries sent in by our readers and the listeners of BBC Radio 4. One question was posed by Philip Le Riche:

“Why do some people faint at the sight of blood, or a hypodermic needle, or even if they bash their funny bone? Does it serve any useful evolutionary purpose, or is just some kind of cerebral error condition?”

Watch the animation above to find out what’s happening in the brain when we fall unconscious.

You can also listen to the Radio 4 series podcast to discover much more about fainting: Adam Rutherford is strapped onto a hospital tilt table in an attempt to make him black out and Hannah Fry receives an aromatic surprise.

If you have any scientific cases you would like the team to investigate please email: curiouscases@bbc.co.uk

Watch another animation from the Rutherford and Fry series: Are you a redhead without realising?

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