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| Parts of the Nervous System - Peripheral Nervous System |
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| The peripheral nervous system is made up of nerves that connect the different parts of the body (peripheral tissues) to the central nervous system. |
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| As mentioned earlier, there are three types of nerves based on their composition: |
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 sensory (afferent) |
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motor (efferent) |
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mixed |
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| The nerves are also classified as follows: |
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| Cranial nerves are those that connect the different parts of the body to the brain. There are 12 pairs of cranial nerves. Cranial nerves may be sensory, motor or mixed. |
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| For example: |
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| 1st and 2nd pairs of cranial nerves are Olfactory (pertaining to smell) and Optic (pertaining to sight) respectively. They are both sensory in nature. |
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| The 4th pair is trochlear nerves that are motor and help in the movement of the eyeball muscle. |
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| The 7th pair of nerves is the facial nerves that control the taste buds, salivary glands, facial and neck muscles. These nerves are mixed nerves. |
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| There are 31 pairs of spinal nerves. The spinal nerves are all mixed having both sensory and motor fibres. The sensory fibres and motor fibres separate just before entering the spinal cord into dorsal root and ventral root. |
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| The Dorsal Root |
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| The dorsal root is made up of the following: |
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| Dorsal Root Ganglion |
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| It is a collection of the sensory nerve cell bodies. (Ganglia are centres of collection of nerve cell bodies). |
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| Sensory or Afferent Nerve Fibres |
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| Sensory or afferent nerve fibres conduct messages from the peripheral tissues to the spinal cord. They finally join the grey matter of the spinal cord. They produce the sensation of touch, pain or reflex actions (involuntary movements). |
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| The Ventral Root |
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| The ventral root contains only the motor nerve fibres that conduct messages from the spinal cord to the peripheral tissues. The nerve cell bodies of the motor nerves are in the grey matter of the spinal cord. |
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