Nerve cell / Neuron
- The neuron or nerve cell is a structural and functional unit of the nervous tissue.
- These neurons help to transmit signals to and from different parts of the body
- These signals are in both electric and chemical forms . (We will discuss this a little later in this chapter)
Structure of Neuron
A neuron has three parts — the cell body , dendrites and axon .
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Part |
Details |
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Dendrites |
Branched structure that collects information from previous neuron and passes on to the cell body . |
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Cell body |
It is the broad, rounded part of the neuron that contains the nucleu s,abundant cytoplasm ( neuroplasm ) and other organelles like mitochondria, endoplasmic reticulum, Golgi body etc. |
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Axon |
It is a long tube-like structure that carries information from the cell body to the nerve endings . Axon is covered by 1-2 sheaths called nerve fiber . A number of nerve fibers joined together to form a nerve . |
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Nerve endings |
The axon is branched terminally in muscle fibers, glands, other structures or forms synapse with the dendrites of other neurons. |
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Synapse |
There is a gap between the nerve endings of one neuron and dendrite of the following neuron where signals are transmitted as chemical signals called neurotransmitters. |
How exactly do these signals pass through and between neurons?
To sum up,
- Signals go from;
Dendrites → cell body → Axon → Nerve endings → Synapse → Dendrite of next neuron.
- Signals are in the form of electric impulses as they pass from dendrites to nerve endings .
- Signals are in the form of chemicals called neurotransmitters during transmission of messages across the synapse .
Different types of neurons
The different types of neurons are
1. Sensory neurons - They carry information from the receptors in the sense organs to the brain .
These are also called Afferent neurons.
Example: When we hear a sound, the signal is carried from the inner ear to the brain.
2. Motor neurons - They carry information from the brain cells to the effector organ that need to respond according to the signal sensed.
These are also called Efferent neurons.
Example: The brain cells transmit signals to the muscle cells in the hand enabling us to remove our hand from a hot surface
3. Interneurons - They carry information from the sensory neuron to motor neurons.
