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.
Names and functions of the 31 pairs of spinal nerves
The 31 pairs of spinal nerves are named based on the vertebral levels they emerge from, and they have both sensory and motor functions. Here is a list of names and functions of the 31 pairs of spinal nerves:
Cervical Nerves (C1-C8):
- C1 nerve: Suboccipital nerve, responsible for controlling the movement of the head
- C2 nerve: Greater occipital nerve, responsible for providing sensation to the back of the head
- C3-C5 nerves: Responsible for controlling the diaphragm, the main muscle involved in breathing
- C5-C8 nerves: Brachial plexus nerves, responsible for controlling the shoulder, arm, and hand muscles
Thoracic Nerves (T1-T12):
- T1-T6 nerves: Intercostal nerves, responsible for providing sensation to the chest wall and controlling the muscles involved in breathing
- T7-T12 nerves: Thoracoabdominal nerves, responsible for controlling the abdominal muscles and providing sensation to the abdomen and back
Lumbar Nerves (L1-L5):
- L1-L2 nerves: Iliohypogastric and ilioinguinal nerves, responsible for providing sensation to the lower abdomen, groin, and upper thigh
- L2-L3 nerves: Genitofemoral nerve, responsible for controlling the muscles involved in hip and knee flexion and providing sensation to the groin and inner thigh
- L3-L4 nerves: Femoral nerve, responsible for controlling the quadriceps muscle and providing sensation to the front of the thigh
- L4-S1 nerves: Sciatic nerve, responsible for controlling the hamstrings and calf muscles and providing sensation to the back of the thigh and leg
Sacral Nerves (S1-S5):
- S1-S2 nerves: Superior and inferior gluteal nerves, responsible for controlling the gluteal muscles and providing sensation to the buttocks and posterior thigh
- S2-S4 nerves: Pudendal nerve, responsible for controlling the pelvic floor muscles and providing sensation to the genitalia and anus
- S2-S5 nerves: Sciatic nerve, responsible for controlling the hamstrings and calf muscles and providing sensation to the back of the thigh and leg
Coccygeal Nerve (Co1):
- The coccygeal nerve controls the skin around the coccyx and the muscles of the pelvic floor.
The sciatic nerve starts just outside the base of your spine (lumbar spine and sacral region). It runs through the top of your gluteus muscles (butt) and down the back of your thighs (hamstrings) and lower legs (calves).
Conclusion
The human nervous system is a complex and highly specialized network of cells and structures that allow us to interact with our environment and control our bodily functions. Moreover, the spinal nerves are responsible for transmitting sensory information from the skin, muscles, and organs to the spinal cord and the brain, as well as carrying motor impulses from the spinal cord to the muscles and glands.
Additionally, these nerves also regulate involuntary functions such as digestion, breathing, and heart rate through the autonomic nervous system. Understanding the cranial and spinal nerves and their functions is important in understanding how our body works.