Structure and Function of Neurones

A neurone is a nerve cell specialised to carry electrical impulses. Every neurone has a cell body containing the nucleus, many mitochondria and a lot of rough endoplasmic reticulum for making proteins such as the enzymes that make neurotransmitters. Thin extensions carry the impulses: dendrites carry impulses towards the cell body and the axon carries impulses away from it.There are three types of neurone.Motor neurones carry impulses from the CNS to effectors. The cell body is in the CNS and has many dendrites. A single long axon ends in axon terminals with synaptic knobs on a muscle or gland.Sensory neurones carry impulses from receptors to the CNS. A long dendron carries impulses from the receptor to the cell body, which lies just outside the spinal cord in a dorsal root ganglion, and a short axon carries them into the CNS.Relay neurones (intermediate neurones) are found in the CNS. They are short, with many branched dendrites, and connect sensory neurones to motor neurones and to other neurones.Many vertebrate axons and dendrons are surrounded by a myelin sheath formed by Schwann cells, with small gaps called nodes of Ranvier. The great length of motor and sensory neurones allows a single cell to carry impulses over long distances, such as from the spinal cord to the foot, and the many dendrites allow a neurone to receive impulses from many other neurones.