Your brain is greedy! It accounts for only about 3 per cent of your body weight, but receives about 30 per cent of the blood being pumped by your heart. “The brain is like a spoiled and demanding child, but yet it is extremely smart and efficient,” explains Bennet Omalu, MD, neuropathologist and clinical professor at the University of California. “It takes the brain about 1/10,000th of a second to respond to something and generate an action.”
Certain functions require more energy than others. The brain areas responsible for auditory processing require more energy than the olfactory system or the areas of the brain responsible for memory. Hearing requires very fast and precise signaling — it wouldn’t be advantageous for the sound of danger to be delayed in any way. Relatively slow processes like smell don’t have the same intense energy needs.
The brain doesn’t have a reserve of energy to store away for when it needs it. Unlike muscles, which can store excess carbohydrates, the brain needs to be constantly supplied with oxygen and energy in order to run properly. If the blood supply to the brain is cut off or disrupted — like during a stroke or head injury — neurons start shutting down quickly. This may seem like a flaw, but it is integral to the working of the brain. If the brain contained cells that stored backup power, those cells would take up space in between neurons. This would increase the lengths that electrical signals would have to travel, and they would need more energy to do so. Early organisms may have had nervous systems that included these kinds of fail-safes, but over millions of years of evolution, we sacrificed this backup power for efficiency. It makes us susceptible to injury, but it also allows us to take advantage of the brain’s complex circuitry.
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