Nervous system

The human nervous system consists of:

  • the central nervous system (CNS) – the brain and spinal cord
  • the peripheral nervous system – nerve cells that carry information to or from the CNS
Human body showing the nervous system with the brain and spinal cord labelled.  The brain and spinal cord comprise the central nervous system.

Nerve cells

Nerve cells are also called neurones. They are adapted to carry electrical impulses from one place to another:

  • they have a long fibre (axon) which is insulated by a fatty sheath
  • they have tiny branches (dendrons) which branch further as dendrites at each end
Motor neurone. At one end there is a nucleus surrounded by cytoplasm and dendrite.  All enclosed by a cell membrane.  There is a long tail holding the Axon which connects with the nerve endings.