A nerve impulse is a pulse of electricity, an action potential, that passes along the nerve. The speed at which it travels is called its conduction velocity and in human nerve fibres, this velocity ranges between 1 and 3 metres per second in unmyelinated fibres and between 3 and 120 metres per second in myelinated fibres.
Conduction velocity is affected by several factors - the larger the diameter of the nerve cell axon, the faster the transmisison speed. As you can see from the figures, myelinated fibres transmit at much higher speeds than unmyelinated ones. The speed also depends on the number of nerve cells strung together - When they meet at synapses, the transmission slows down because chemicals need to be used to get the nerve signal across the gap. The greater the number of synapses, the slower the overall speed of nerve signal transmission.
Conduction velocity is affected by several factors - the larger the diameter of the nerve cell axon, the faster the transmisison speed. As you can see from the figures, myelinated fibres transmit at much higher speeds than unmyelinated ones. The speed also depends on the number of nerve cells strung together - When they meet at synapses, the transmission slows down because chemicals need to be used to get the nerve signal across the gap. The greater the number of synapses, the slower the overall speed of nerve signal transmission.