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What is the primary energy source for the human brain?Fabian van den Berg:
The brain mainly relies on glucose, a type of sugar. This glucose is broken down, generating a gradient of hydrogen ions, a process that also requires oxygen, explaining our need to breathe. This creates a dam-like effect with hydrogen concentrated on one side and minimal on the other. The hydrogen ions can only pass through a specialized structure, and as they do, their movement generates ATP, which powers many biological functions, including the activity that keeps neurons firing. (See Fabian van den Berg's answer to "Why do we inhale oxygen and exhale carbon dioxide?" for more information.)
Neurons use a similar gradient mechanism to function. When a signal's voltage becomes sufficient, voltage-gated channels open, allowing sodium to flow in, making the inside more positive. The process continues to adjacent gates, and this chain reaction persists until it reaches the synapses, where neurotransmitters are released to trigger the next neuron (see Fabian van den Berg's answer to "How does opening a sodium channel cause depolarization in a neuron?" for further details).
To maintain a negative charge and reset the neuron after it fires, an active transport process moves ions across the membrane, which consumes energy. This energy is supplied by ATP.
In the end, your brain operates on sugar and oxygen, which fuel the ATP production process in your mitochondria.
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