Like all the other cells in the human body, neurons need
energy to function. In fact, neurons consume an especially
large amount of energy. The brain accounts for only 2% of
the human body's weight, but almost 20% of its energy consumption.
This energy is produced in the mitochondria, elongated organelles dispersed throughout the cell body. These mitochondria use oxygen to extract energy from sugars and fats and to produce molecules of the energy-storage compound adenosine triphosphate (ATP). These ATP molecules are then used to fuel the various chemical reactions that take place within the neuron.