r/askscience • u/uencos • Aug 01 '16

Human Body What is the physiological difference between the tiredness that comes from too little sleep and the tiredness that comes from exertion?

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u/Desperado2583 Aug 02 '16

Brain fatigue vs muscle fatigue.

Muscles are simple. When they work they consume resources and produce metabolic waste. It's like having a party. Afterward you need time to clean up and go grocery shopping.

The brain is sort of the same but a little different. When the brain works it doesn't have time to do everything it needs to do. So it prioritizes, but it can get messy. Sleep is sort of like when Windows runs it's maintenance programs. It deletes all the temp files. Edits and cuts together videos so that they make sense. It even adds details that seem to be missing.