• Question: What makes humans feel tiredness?

    Asked by Zealousy to Susan, Chris on 15 Jun 2015.
    • Photo: Chris Armstrong

      Chris Armstrong answered on 15 Jun 2015:

      Oh man, you’ve asked a big one there.

      Seriously experts in the field in the world still say “because we get sleepy” is the best reason that humans need to sleep.

      ** I will say that this is not my field at all, and what I’m about to say is things I learnt from looking into caffeine addiction… for no reason… **

      The feeling of tiredness though has a better answer than that, theres a drug/hormone in your brain called adenosine which is produced pretty much throughout the day and production of it increases through muscle use and various other factors. This drug/hormone latches on to receptors and slow nerve cell activity causing the drowsiness.

    • Photo: Susan Cartwright

      Susan Cartwright answered on 15 Jun 2015:

      I defer to Chris on this one – I’m not a biologist, a physiologist or a physician!

      However, it does seem that sleep is necessary to good health: people who are subjected to sleep deprivation become seriously unwell, especially as regards mental functioning: they can’t concentrate, have difficulty learning new skills or remembering new information, and experience problems with mood (mood swings, depression, etc.). So feeling tired when you have not had enough sleep is a good evolutionary adaptation, just like feeling hungry when you haven’t has enough to eat: it’s basically a warning sign saying “you are not attending properly to your physical needs: DO SOMETHING.”

      There is a very rare inherited disease called Fatal Familial Insomnia, in which people have a damaged gene for the prion protein (the same one that causes Creutzfeld-Jakob disease and “mad cow” disease). Sufferers become unable to sleep, even with the assistance of sleeping pills. As the name suggests, it is lethal – once the symptoms start, sufferers live for only a year or two. So sleep is necessary, even though we don’t fully understand why, and so feeling sleepy is an essential early-warning sign.

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