Why does our brain consume so much energy? Scientists have found the answer

It is well known to scientists that the human brain is an energy sink. Indeed, this organ burns 10 times more energy than the rest of the human body, consuming when we are at rest up to 20% of what we absorb. Even in comatose people who are brain dead, only 2-3 times less energy is consumed by the brain.

The reason behind this heavy consumption by the brain has always been a mystery in the medical world. But a new study may have discovered the cause. This is a process that takes place in what are called synaptic vesicles.

The article reporting the results of this research was published in the journal Science Advances.

What’s going on in neurons

When a neuron sends a signal to another neuron, it happens through a synapse which is a small gap between the two brain cells.

The first step in transmission is the sending by the first neuron of a group of vesicles at the level of its tail. These vesicles will then take up neurotransmitters from the neuron, acting as “envelopes” for the messages. The “envelopes” are then transported to the edge of the neuron where they will fuse with the membrane while releasing the neurotransmitters into the synaptic gap. Afterwards, these neurotransmitters will come into contact with the receptors of the second neuron, thus getting the message across.

According to scientists, these different stages require a large amount of brain energy, especially when the vesicles merge. But this process takes place in an active brain. One can thus wonder what happens when there is no transmission of messages and when the vesicles do not fuse with the membrane. However, the brain continues to consume energy.

An uninterrupted process

To find out why the brain continues to burn fuel, researchers have developed several experiments on nerve endings. These experiments aimed to compare the metabolic state of synapses in activity and those at rest. Scientists then discovered that even when the endings do not send a message, the synaptic vesicles have high metabolic energy requirements.

The researchers explain that the “pump” that pushes protons out of the gallbladder and absorbs neurotransmitters never seems to stop. Still, it needs a stable flow of energy to function.

During the experiments, it was observed that the pump was behind half of the synapse’s metabolic consumption at rest. Scientists explain that this pump tends to leak, causing synaptic vesicles to constantly eject protons. This happens even if the vesicles are already full of neurotransmitters and the neuron is inactive.

With the high number of synapses in the brain and the presence of hundreds of synaptic vesicles at each nerve ending, this process consumes a very large amount of energy. This is the reason why the brain is so hungry for energy. The researchers say, however, that further study is needed to find out how the different types of neurons behave.

SOURCE: https://www.sciencealert.com/a-hidden-structure-in-our-neurons-could-explain-why-the-brain-guzzles-so-much-energy

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