Believe it or not, there are over 7 trillion nerves in the human body. All these nerves are part of what’s known as your body's nervous system. You can think of nerves as your body's electrical wiring — they transmit signals between your brain, spinal cord, and the rest of your body. Find out more about what these nerves do and what makes them important below.
What Is the Nervous System?
The nervous system consists of two components:
- The central nervous system, which is made up of the brain, spinal cord, and nerves
- The peripheral nervous system, which is made up of sensory neurons, clusters of neurons called ganglia, and other nerves that connect to one another as well as the rest of the central nervous system
These nerves and cells, called neurons, send messages throughout your body. All nerves are important for proper day-to-day functioning, but there are two groups of nerves chiropractors focus on the most: cranial and spinal nerves.
Cranial nerves are located on the bottom surface of your brain. There are 12 pairs of them, and they each have their own special function. These cranial nerves connect your brain to different parts of your head, neck, and trunk.
To prevent confusion (and because these nerves are located so close together), each pair is numbered with a Roman numeral, beginning at the front and moving to the back.
For example, the first nerve closest to the front of your head is the olfactory nerve, so its Roman numeral designation is I.
Most of the time, cranial nerves are classified as being either sensory or motor. Sensory refers to your five senses — touch, smell, taste, hearing, and sight — and motor nerves are responsible for controlling the movement and function of glands or muscles.
Take a closer look at individual cranial nerves below.
Olfactory Nerve (I)
The olfactory nerve is responsible for your sense of smell. It sends information to your brain about smells you encounter.
When you smell something pleasant, such as bread baking, the aromatic molecules dissolve at the roof of your nasal cavity, which stimulates receptors to generate nerve impulses. These nerve signals are then sent to the areas of your brain that deal with memory and smell recognition.
Optic Nerve (II)
The optic nerve is essential for proper vision, and both of your eyes have one.
When light first enters your eye, it comes in contact with receptors in your retina, called rods, which help you see black and white images and in the dark, and cones, which are responsible for color vision.
Your rods and cones receive this information and pass it along to your optic nerve. The signal continues traveling along this optic nerve pathway until it reaches the visual cortex in your brain, which processes the information and ensures you can see clearly.
Oculomotor Nerve (III)
The word oculomotor is comprised of two parts: oculo, which relates to the eye, and motor, which can refer to movement or muscles.
The oculomotor nerve, then, helps control your eyes' muscle movements. It provides movement for the eyeball and upper eyelid while also assisting with the eyes' involuntary functions, including pupil contraction and automatic lens adjustments (this is what happens when your eyes automatically focus on near or far objects).
Trochlear Nerve (IV)
The trochlear nerve is also involved in eye movement. It controls the muscle in the eye that enables it to point downward and inward.
Trigeminal Nerve (V)
The trigeminal nerve is the largest cranial nerve in the human body, and it has both motor and sensory functions.
The trigeminal nerve assists you with chewing and clenching your teeth, and it provides sensation to muscles in your eardrum.
The trigeminal nerve's sensory functions are divided into three parts, each of which connect to sensory receptor sites on the face.
- Ophthalmic: Provides sensation for parts of the eye, nose, eyelid, and forehead
- Maxillary: Gives sensation to the middle third of the face, upper teeth, eyelid, and side of the nose
- Mandibular: Provides sensation to the lower third of the face, tongue, mouth, and lower teeth
Abducens Nerve (VI)
The abducens nerve also helps with eye movements, in particular, movements that involve your gaze moving outward.
Facial Nerve (VII)
Like the trigeminal nerve, the facial nerve also has motor and sensory functions. It controls:
- Movement of muscles that produce facial expression
- Facial gland movement
- Sensation in the external ear
Vestibulocochlear Nerve (VIII)
The vestibulocochlear nerve actually consists of two nerves in one, the vestibular nerve and cochlear nerve.
- The vestibular nerve helps your body sense changes in the position of your head, and your body uses this information to help it maintain its balance.
- The cochlear nerve helps you with hearing and determines a sound's frequency and magnitude.
Glossopharyngeal Nerve (IX)
As with other cranial nerves, the glossopharyngeal nerve has both sensory and motor functions.
Its sensory function receives incoming information from the back of your mouth, including the tongue, tonsils, and throat. It is also involved with taste sensation for the back of your tongue. Its motor functions are also in the throat, as it's what allows the muscles in your throat to shorten and widen.
Vagus Nerve (X)
- Sensory Functions: Provides sensation to the outer ear, throat, heart, and abdominal organs
- Motor Functions: Gives movement to the soft palate and throat
- Parasympathetic Functions: Regulates heart rhythm and supplies nerves to smooth muscles in your gastrointestinal tract, lungs, and airway
Doctors often use vagus nerve stimulation therapy to treat conditions such as epilepsy, depression, and anxiety. The vagus nerve is also the longest of all the cranial nerves because it begins in the medulla in the brain and extends all the way to the abdominal area.
Accessory Nerve (XI)
This cranial nerve, the accessory nerve, provides motor function to some of the muscles in the neck. It's what lets you rotate, flex, and extend your neck and shoulder muscles.
Hypoglossal Nerve (XII)
The last of the cranial nerves is the hypoglossal nerve. It provides necessary motor functions to the tongue muscles.
The spinal cord is part of your central nervous system. It begins at the bottom of the brain stem and continues down to your lower back.
There are 31 pairs of spinal nerves, and they control sensory, motor, and other functions of your body. They transmit messages between your spinal cord and the rest of the body, including skin, muscles, and internal organs. Each spinal nerve is responsible for providing sensation to a different area of your body.
To help identify them, spinal nerves have alphanumeric figures assigned to them:
- C1-C8: Cervical nerves
- T1-T12: Thoracic nerves
- L1-L5: Lumbar nerves
- S1-S5: Sacral nerves
- One pair of coccygeal nerves
Each group of spinal nerves is involved with movements in certain parts of your body, including your hands, fingers, arms, upper back, hips, and abdominal muscles. Some spinal nerves are even responsible for ensuring you can walk and run properly.
For more detail on spinal nerves' functional ability, refer to the chart below.
Some nerves in the spinal cord are responsible for controlling automatic body functions, such as your heart rate, breathing, and other things your body does automatically.
For example, spinal nerves T1-L5, which are your thoracic and lumbar nerves, are partially responsible for controlling the functions of your:
- Gastrointestinal system
- Sweat glands
The upper part of your sacral nerves, from L5-S3, are responsible for controlling bladder and bowel movements.
At Northeast Spine and Sports Medicine, we help our patients feel more comfortable in their everyday lives by addressing problems they might experience with nerves in their brain or spinal cord. We offer treatments such as spinal decompression therapy, treatment for sciatica, and many other chiropractic services.
If you have questions about cranial or spinal nerves or think you might be a good candidate for chiropractic care, give us a call at 732-653-1000 or book an appointment online.