What does it mean, biologically, when your brain is "fried"?

Answered on August 19, 2014
Created March 12, 2013 at 2:04 AM

Anybody ever had a long day when at the end your brain is just completely done?

What's really going on biologically? Does anyone know?

My guess is that this simply means your brain has used up all available energy, specifically glucose and ketones. However, this probably assumption probably doesn't hold up as there are I can probably go run a couple miles after work. This would mean that my blood supply still has plenty of glucose and ketones, and other sources of energy. Perhaps I need to wait a while until these resources cross my blood brain barrier? If there is some sort of a short time delay in provided resources from the blood to the brain, then perhaps this is why taking a short "power" nap could provide one with another several hours of mental stamina.

I guess from knowing the reason why this problem occurs, I'd hope to better understand how we can extend mental stamina.

People take Adderall to stay focused longer, and apparently that increases the concentration of certain neurotransmitters. But what is a more natural approach?

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2 Answers


on March 12, 2013
at 02:32 AM

At the end of a long, stressful day, you likely haven't been breathing adequately. When we are healthy and relaxed, we breath through our nose, but stress and exhaustion make us breathe through our mouths. Breathing through your nose keeps your brain cool and alert. Yawning is thought to be a way cool the brain down, as it warms when we are breathing through our mouths which makes us foggy. If you feel foggy, breathe through your nose and see if it helps.



on March 12, 2013
at 02:43 AM

Typically a "fried brain" at the end of the day is the symptom of a sugar crash -- your blood sugar is too low. You can still run because muscles have their own supply of glycogen and are not as dependent on blood sugar as brain is, but I bet if you actually try to do it, chances are you'll feel weak/faint-y very soon.

Of course it's also possible to be "just" mentally tired if you didn't get enough sleep, had a truly stressful, exhausting day, etc.

If it happens to you regularly, you can try a little experiment. About an hour before your brain usually konks out, eat some carbs/sugar. A few fruits or a bowl of rice, or something like that. If that does prevent your brain from going into zombie mode, well, now you know the cause.

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