NERVE IMPULSES
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.
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