Neuron
What is a Neuron?
Can Nerves Heal?
Nerve Roots
A nerve root is the short section of a nerve that connects directly to the spinal cord. There are two roots at the spine: the dorsal and ventral.
Just beyond the spinal cord, these two roots join to form a spinal nerve that travels out to a specific region of the body. When people refer to a pinched nerve in the neck or low back, they are often talking about irritation or compression at the nerve root.
- Ventral Roots (Efferent): Carries motor commands away from the central nervous system to the body.
- Dorsal Roots (Afferent): Caries sensory information into the spinal cord from the body.
- Mixed Nerves do not have a single mixed root, but instead are the fusion of two separate roots after they exit the spinal cord.
What are Ganglia?
Ganglia are clusters of nerve cell bodies located outside of your central nervous system. In the sensory system, the dorsal root ganglia contain cell bodies of sensory neurons that bring information from the body to the spinal cord.
Other ganglia, such as those in the autonomic nervous system, contain cell bodies that regulate automatic functions like heart rate, digestion, and sweating. Some of these are involved in interoception, signals that inform the brain about the body’s state. These largely travel through visceral sensory pathways.
Many interoceptive pathways have cell bodies in ganglia outside the spinal cord and brainstem, such as the nodose and jugular ganglia associated with the vagus nerve, cranial nerve ganglia, and certain autonomic and visceral ganglia. These ganglia help carry information about heart rate, gut sensations, blood pressure, and internal organ status toward the central nervous system, where the brain uses it to create interoceptive awareness.
Learn more about interoception by reading somatosensory awareness.
- Sensory Ganglia: Contain the cell body of afferent (sensory) neurons. Sensory ganglia transmit interoceptive signals.
- Autonomic Ganglia: Autonomic ganglia receive efferent signals from the central nervous system.
Afferent and Efferent Nerves
Afferent nerves carry information toward the central nervous system; they are the sensory pathways that bring information from the body, such as touch, temperature, and nociception.
- Afferent Signals: Nerve impulses carrying sensory information from the body receptors toward the CNS.
- GSA: General somatic afferent signals from the skin, skeletal muscles, and joints.
- GVA: General visceral afferent signals from the internal organs.
- Efferent Signals: Nerve impulses from the CNS sent to the muscles, glands, organs, and autonomic systems.
- GSE: General somatic efferent signals are motor commands to skeletal muscles to create voluntary movement.
- GVE: General visceral efferent signals to smooth muscle, cardiac muscle, and glands.
Broad GSA Fibers
On a microscopic level, GSA fibers handle only one specific type of data, meaning they are attached to a specialized sensory receptor and will not send mixed signals, because they are hardwired to respond to one type of stimulus.
However, while an anatomy textbook may state that a GSA handles only one specific type of sensory information, a broad GSA is composed of millions of specialized fibers that work together to collect all sorts of sensory data.
Imagine listening to an orchestra. The orchestra represents the broad GSA category, while individual musicians represent the highly specialized, hardwired GSA fibers.
When you look at the stage, you see one collective group called the symphony. They are all working together to play one beautiful song.
Within that orchestra is a violinist named Reanna. Reanna is a specialist; her sheet music contains only violin notes, and she isn’t going to grab a bongo mid-song and start pounding away on it. She has her purpose, and as a specialist, she does it well.
When a cool breeze hits your skin, only the flute section plays its specific notes. When the brain hears their specific tone, it instantly recognizes it as cold. The complex makeup of the orchestra is what allows us to hear magnificent melodies and songs without it sounding like a cacophony of noise.
GSA fibers process exteroceptive signals to the spinal cord and brain. These signals include touch and pressure (mechanoreception), temperature (thermoception), noxious stimuli (nociception), and vibration. Additionally, GSA fibers collect proprioceptive data, which helps us identify body position and where our limbs exist in space.
Pain is neither an afferent nor an efferent signal.
Data sent to the brain does not have a sensation (afferent signals). Pain and pleasure are not felt in the place where we perceive them to have originated; they are experienced within our somatosensory map.
All sensation, and pain is an output, produced after raw data has been collected and translated by the brain into a sensation or an emotion. Like the X on a treasure map, this is where our brain decides to place our pain.
Examples of the afferent input our brain receives as raw data are interoception, exteroception, and nociception. None of these inputs has a sensation on its own; they must first be processed by the brain to be experienced.
Raw Data Isn’t Felt
A music album on a CD that hasn’t been played is just a piece of plastic with data encoded on it. While the information on that CD could play a song, it is just data until it is played for someone to hear. For the CD to inspire an emotion, it first must be heard.
Our somatosensory system works the same way. The information being collected by our sensory (afferent) neurons is just data until the brain receives and interprets it. Once it does, it is then that we experience peace, pleasure, and pain.
Take the Next Step
If these concepts help you understand your pain more clearly, pain management coaching can help you apply them to your own experience. Together we can explore practical ways to help you discover safety within.
Learn more about pain management coaching.
Disclaimer
All information provided on this website, including, but not limited to, educational materials, pain neuroscience explanations, treatment suggestions, and any other content shared during sessions, classes, or coaching, is for educational purposes only. It is not intended to diagnose, treat, cure, or prevent any disease or medical condition, nor is it a substitute for professional medical advice, diagnosis, or treatment.
You should always consult a qualified healthcare provider for medical concerns, and never disregard professional medical advice or delay seeking it because of information you receive here.
Jennifer Brand Spa
Pain Management at 2717 Hwy K, O’Fallon, MO 63368