The human nervous system is a complex network of cells and structures that is responsible for transmitting electrical impulses throughout the body. It is made up of neurons and nerve fibers that allow us to interact with our environment and control our bodily functions. In this article, you will learn two important components of the human nervous system: the 12 pairs cranial nerves and the 31 pairs spinal nerves.
The 12 Pairs Cranial Nerves
The human body has 12 pairs of cranial nerves that emerge directly from the brain. Each cranial nerve has a specific function, such as controlling facial movements and expressions, transmitting the sense of smell, or helping with hearing and balance. The cranial nerves are as follows:
- Olfactory nerve – responsible for the sense of smell
- Optic nerve – transmits visual information from the eyes to the brain
- Oculomotor nerve – controls eye movements and the size of the pupil
- Trochlear nerve – controls eye movements
- Trigeminal nerve – controls sensations in the face and mouth, as well as chewing
- Abducens nerve – controls eye movements
- Facial nerve – controls facial movements and expressions
- Vestibulocochlear nerve – helps with hearing and balance
- Glossopharyngeal nerve – controls swallowing and taste sensations
- Vagus nerve – controls many internal organs, including the heart, lungs, and digestive system
- Accessory nerve – controls movements of the neck and shoulders
- Hypoglossal nerve – controls movements of the tongue and swallowing
The 31 Pairs Spinal Nerves
The human body also has 31 pairs of spinal nerves that emerge from the spinal cord. The spinal nerves are responsible for controlling functions in the rest of the body, including the arms, legs, and internal organs. Spinal nerves are divided into five main categories based on where they emerge from the spinal cord: cervical nerves, thoracic nerves, lumbar nerves, sacral nerves, and coccygeal nerves.
In total, there are 31 pairs of spinal nerves grouped regionally by spinal region. More specifically, there are eight cervical nerve pairs (C1-C8), twelve thoracic nerve pairs (T1-T12), five lumbar nerve pairs (L1-L5), 5 sacral (S1-S5), and a single coccygeal nerve pair.