ABSTRACT
A neuron consists of a cell body (perikaryon) and its processes. Neurons vary considerably in shape and size, ranging from the small granule cells of the cerebellum that measure about 5m in diameter to the larger motor cell in the ventral horns of the spinal cord that measure up to 120m in diameter. Each possesses a single axon that also varies considerably in length, ranging from a few millimeters to up to 90 cm. The number of its dendrites varies from one to as many as 80, according to the type of neuron. Whatever their size or function, neurons share certain features: they have a high metabolic rate, they are vulnerable to lack of oxygen and/or glucose, and in postnatal life they lose the ability to multiply.
