The message and the messenger
Show on a big screenA bell rings. You hear it at once. Nerve cells carry the signal fast.
- A dendrite picks up the signal.
- It reaches the cell body.
- The axon carries it, as an electrical signal.
- It reaches the nerve ending.
- Two nerve cells, almost touching.
- A tiny gap sits between them.
- A chemical crosses the gap.
- It goes one way only.
Send a signal along a neuron. Find where it turns chemical.
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A neuron is a nerve cell. Its dendrite picks up a signal. The signal moves through the cell body and along the axon. The axon is the long, thin part of the cell. It reaches the nerve ending. Inside a neuron, the signal is electrical.
Two neurons do not touch. A tiny gap lies between them. The gap is a synapse.
At the nerve ending, the signal releases a chemical. The chemical crosses the gap. In the next neuron, the chemical starts a new electrical signal. Only the first neuron's nerve ending releases the chemical. So the signal crosses one way only.
A synapse can also pass signals to muscles and to glands. Glands are parts that release chemicals.
The rule
A neuron is a nerve cell. It carries a signal as electricity, one way, dendrite to nerve ending. At a synapse, it crosses as a chemical to the next cell.
For example, incense smoke reaches the nose. Receptors there, cells that sense smell, start a signal. Neurons carry it on to the brain.
Try the lab to finish this lesson.