Body organs aren't all internal like the brain or the heart. There's one we wear on the outside. Skin is our largest organâadults carry some 8 pounds (3.6 kilograms) and 22 square feet (2 square meters) of it. This fleshy covering does a lot more than make us look presentable.
The brain sends messages through the spinal cord and nerves of the peripheral nervous system to control the movement of the muscles and the function of internal organs. The basic working unit of the nervous system is a cell called a neuron.
The core component of the nervous system in general, and the brain in particular, is the neuron or nerve cell, the brain cells of popular language. A neuron is an electrically excitable cell that processes and transmits information by electro-chemical signalling.