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Above: Structure of a typical neuron
Neurons – A whistle-stop Tour
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stained pyramidal neurons in
cerebral cortex
By the end of this session you should be able to
answer the following:
What is: An axon?
What is a ‘spike’?
How many molecules are there in a
neurotransmitter?
What does a dendrite do?
Why is there a picture of a AA battery on this page?
What is in the synaptic cleft?
Is synaptic transmission electrical, chemical, or both?
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How Neurons Work
Synaptic Transmission
Neurons communicate by chemical and electrical synapses when
an electrical impulse is transmitted from one neuron to another
along the AXON. This happens at a molecular level.
At synapses, the ends of axons (called axon terminals)
nearly, but not actually touch the next neuron.
Axon terminals contain many synaptic vesicules loaded
with 2000 molecules of a specialised compound called
a neurotransmitter.
An electrical impulse called a ‘spike’ sends electrical
impulses down the axon.
Waiting for the ‘spike’ from the neurotransmitter is a
receiver, called the dendrite.
Between the axon terminal of one neuron and the
dendrite is a tiny saltwater-filled gap called the
synaptic cleft.
The brain can transmit between 400 to 1,200 spikes per
second, but cannot go at the top rate for more than a
few seconds. A typical ‘spike’ requires 70 millivolts , or
one-twentieth of the power in an AA battery.
(adapted from The Accidental Mind, D.J. Linden)