Why does the brain need so much energy?
The fact that the brain consumes more energy than any other organ, and spends up to 20% of all the capacities produced by the body has been known for a long time. Until now, experts have been of the opinion that the bulk of this energy is spent on the interaction of neurons with each other.
Scientists at the University of Minnesota have found that the brain spends about two–thirds of its energy budget on generating nerve impulses, and the remaining third on maintaining the normal state of cells. The authors came to this conclusion based on the processing of images obtained using magnetic resonance spectroscopy, used to assess the level of energy production during changes in brain activity. They claim that this method, which has been used for more than 30 years and allows tracking the fate of metabolic products in various tissues, may be useful in the future for detecting brain defects, tumors or early symptoms of neurodegenerative diseases.
Scientists used magnetic resonance spectroscopy to study the activity of synthesis of adenosine triphosphate (ATP) – the main source of cell energy – in the brain of rats. To do this, the equipment was programmed to detect a combination of three phosphorus atoms in the body, which is part of each ATP molecule. The aim of the work was to study the possible relationship between ATP production and brain activity by measuring the amount of energy released by the brain at different levels of activity.
As expected, the level of ATP production varied significantly depending on brain activity. When knocking out rats, ATP was produced in their brains 2 times less than in a state of mild anesthesia. The authors argue that in an inactive state, the brain spends energy mainly on maintaining the vital activity of cells, while additional ATP synthesized in a more conscious state is spent on other brain functions. According to their estimates, only about a third of the ATP synthesized by the fully awake brain is spent on maintaining the vital activity of cells, and the rest is spent on other functions.
Maintaining the normal state of neurons is necessary for the full functioning of brain tissue and the normal course of many biological processes in the brain, including interneuronal interactions. Charged ions of sodium, potassium and calcium constantly move through the membranes of nerve cells, ensuring their recharge and generation of nerve impulses. These processes require significant energy expenditure, and their violations can lead to the accumulation of ions inside cells, their swelling and death.
The authors obtained similar results when studying the energy expenditure of the cat's brain, which increased significantly with visual stimulation of the animal. In the near future, they plan to conduct similar experiments involving humans.
Portal "Eternal youth" www.vechnayamolodost.ru based on the materials of Scientific American07.05.2008