Simon Laughlin , professor in the department of zoology at Cambridge University, explains why the brain needs so much energy, how it uses energy, and how those needs have affected our evolution.
The exact percentages are difficult to ascertain, but we have pretty good estimates of where that energy is going, though it varies by the area of the brain. These numbers seem to be very similar in humans. The bulk of that energy is consumed at the synapses — the tiny gaps between brain cells where signals are sent and received.
There, the cells are steadily pumping ions into the gap between cells — exchanging potassium and sodium to create electrical charges. This pumping action is fundamental to the operation of brain circuits, but they are very energy intensive.
Between the two major types of tissue in the brain — gray matter and white matter — gray matter requires far more energy than white matter. White matter, made up of bundles of axons, contains large amounts of myelin, the fatty substance that wraps around axons to insulate them and keep electricity from leaking out. Because of this insulation, white matter uses about 20—25 percent as much energy as gray matter, which is made up of dendrites, cell bodies, and the sites of synapses.
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. There are two important factors to keep in mind. The brain requires this expensive electrical power to operate.
And your brain never shuts off. While you rest, your neurons are constantly communicating, updating each other on what is happening. Their constant vigilance is where the bulk of the energy is consumed. You can see the increase on an fMRI scan — the area will be bright red where the circuits are especially active. Despite what you might assume from the bright colors, the energy increase is minor — about eight percent at most.
For all of the agony, and the diets, and the money spent on weight loss products, losing weight is really pretty simple. If the body burns more calories than it takes in, the body will lose weight. It turns out that when the body is resting—not doing anything besides the requirements of basic living such as breathing, digesting food, maintaining body temperature and keeping the blood flowing—the body burns about to percent of its overall energy simply coordinating those activities.
Children use even more brain energy as their brains develop. They need our cells and our cells need them. However, mitochondria can deteriorate as we age. This is why mitochondrial dysfunction lies at the core of many human diseases, including inherited mitochondrial diseases and possibly more common age-related diseases such as dementias and cancer. Understanding how cells can adapt and repair mitochondria is important for improving outcomes for people with mitochondria-related disorders.
The next frontier is to understand the nanoscopic mechanics of how this occurs and identify possible interventions to prevent mitochondrial damage, or improve damage repair, so that we can treat disease and, ultimately, prolong cell and neuron function in the face of ageing and disease.
Main image: A mitochondrion, seen by coloured transmission electron micrograph TEM. Mitochondria are found inside cells and are the energy powerhouses. Credit: Science Photo. Support our research Give now. QBI newsletters Subscribe. Skip to menu Skip to content Skip to footer.
0コメント