NERVE IMPULSES

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What are nerve impulses?

A nerve impulse is an electrical signal that travels along an axon. There is an electrical difference between the inside of the axon and its surroundings, like a tiny battery. When the nerve is activated, there is a sudden change in the voltage across the wall of the axon, caused by the movement of ions in and out of the neuron. This triggers a wave of electrical activity that passes from the cell body along the length of the axon to the synapse.
The speed of nerve impulses varies enormously in different types of neuron.For the impulse to travel quickly, the axon needs to be thick and well insulated. This uses a lot of space and energy, however, and is found only in neurons that need to transfer information urgently.

HOW DO NERVE IMPULSES CODE INFORMATION?



Nerve impulses are a way of coding information, in a similar way to FM radio, allowing information to be transmitted both quickly and accurately. Each impulse is the same size so it is the frequency that carries information about the intensity of the signal. For example, as you turn up the dimmer switch on your bedroom light, the size of the nerve impulses from your eye stays the same but the rate at which they are generated increases.

WHAT IS MYELIN?

Neurons that need to transmit electrical signals quickly are sheathed by a fatty substance called myelin. Myelin acts as an electrical insulator, and signals travel 20 times faster when it is present



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