Nerves

The basic unit of the nervous system is a nerve cell or neuron. Bundles of neurons are called nerves in the PNS and tracts in the CNS

• Neurons are bound together into bundles by connective tissue called perineurium • inside the bundles the neurons are surrounded by delicate connective tissue called endoneurium • the entire nerve is surrounded by a sheath of connective tissue, the epineurium • an artery and a vein occur between the bundles, to nourish the fibres and remove waste

Nerves carry impulses from receptors to the CNS and from the CNS to effectors to bring out appropriate responses