It produces all your thoughts and controls nearly all your actions by communicating with the rest of the body through the nervous system. This consists of the brain plus the spinal cord , which is the bundle of nerves running down the spine. From the central nervous system, tiny threads of nerves branch out all over the body. Then motor nerve s carry instructions from the brain to prod the muscles into motion. Nerve cells Signals pass through nerve cells as impulses of electrical energy.
Every neurone is made up of a cell body and long thread-like fibres.
A nerve contains many nerve fibres, each with its own insulating sheath. Inside the main cell body of every neurone is a nucleus, which controls the activity of the cell. Nerve fibres end in a network of fine branches called dendrites , that make contact with dendrites from other cells to form a synapse . At each synapse there is a small gap, across which a chemical transmitter passes to take the signal to the next neurone. The human brain looks rather like a huge walnut, with a wrinkled surface split into two halves.