The Anatomy of the Ganglia

"Ganglia" is the plural of the word "ganglion." Ganglia are clusters of nerve cell bodies found throughout the body. They are part of the peripheral nervous system (PNS) and carry nerve signals to and from the central nervous system (CNS). Ganglia are divided into two broad categories: the sensory ganglia and the motor ganglia (which are associated with the autonomic nervous system). 

This article discusses the anatomy and function of ganglia, as well as their associated conditions and treatments.

Anatomy

Ganglia are clusters of nerve cell bodies.

Neurons (nerve cells), which are considered the building blocks of the nervous system, typically have three parts:

• Cell body (which contains the nucleus)
• Axon (a long thin structure that sends signals from the cell body to other neurons)
• Dendrites (branched structures that receive input from other cells)

Structure 

There are two types of ganglia in our bodies—sensory and motor:

• Sensory ganglia are ovoid in shape and contain oval cell bodies with nuclei that form in a circular pattern. 
• Motor ganglia, which are located in the spine, form a long chain from the base of the skull down to the tail end of the spine. Motor ganglia contain irregularly shaped cell bodies.

Location

Sensory ganglia locations include:

• Dorsal roots of spinal nerves
• Roots of some cranial nerves like the trigeminal nerve

One portion of these sensory ganglia connects to the PNS. The other is connected to the CNS via the brain or spinal cord.

Motor ganglia locations include:

• The spinal cord: These are called the paravertebral ganglia.
• Internal organs: These include prevertebral ganglia and terminal ganglia.

Motor ganglia are part of the autonomic nervous system (ANS). The ANS controls involuntary movements and functions, like your breathing.

Function 

Ganglia function as the relay stations of the body's nervous system: As one nerve enters a ganglion, another nerve exits it. Ganglia play an essential role in connecting the parts of the peripheral and central nervous systems. 

Motor Function 

Motor ganglia can:

• Receive information from the CNS to regulate and control involuntary movements and functions. Involuntary functions include those of organs such as the heart and lungs.
• Send information to the CNS from these organs

Sensory Function 

Sensory ganglia, or dorsal root ganglia, can:

• Send sensory information to the CNS: This information includes touch, smell, taste, sound, and visual stimuli.
• Send other information to the CNS about body position and sensory feedback relating to organs: For example, if your stomach hurts, the sensory neurons of the PNS are sending a message through the sensory ganglia to your CNS that something is not right.

Associated Conditions

There are a number of conditions that can affect the ganglia in the body.

Conditions Affecting Ganglia in the PNS

Damage to the ganglia in the PNS can cause a variety of neurological problems. Symptoms depend largely on which types of ganglia are affected.

For example, glaucoma is the result of vision-related ganglia damage. Similarly, an injury to the dorsal root ganglia in the spine, such as spinal vertebrae compression, can cause sensory issues, like tingling in the feet.

Conditions that affect the PNS can also impact the ganglia. Damage to the PNS can happen due to:

• Injuries
• Infections
• Genetic abnormalities 
• Genetically inherited disorders
• Tumors
• Problems with blood flow 

Conditions Affecting the Basal Ganglia

Conditions or injuries that may affect the basal ganglia include:

• Head trauma
• Brain tumors
• Infection
• Poisoning 
• Drug overdose
• Stroke
• Multiple sclerosis (MS)

The following conditions are known to affect the basal ganglia in the brain and voluntary movement:

• Parkinson’s disease
• Huntington’s disease
• Dystonia
• Progressive supranuclear palsy

Unsurprisingly, conditions or injuries involving the basal ganglia are extremely serious and often lead to permanent disability or death. 

Treatment 

Treatment may vary depending on the cause of ganglia damage. It also depends on which ganglia have been damaged. 

Some causes of basal ganglia damage, for instance, are reversible and respond well to rehabilitation. Treatments are also available for heavy metal poisoning. Depending on the individual, there may not be any lingering symptoms after treatment. 

However, in the case of Parkinson’s disease, damage to the basal ganglia is part of a progressive illness. Currently, there’s no cure for this disease. Degenerative diseases that affect ganglia in the PNS may not be treatable.

People with severe head trauma that impacts the basal ganglia may not recover. If they do, they may end up with a permanent disability.

Summary

Ganglia are clusters of nerve cell bodies located in the PNS. The basal ganglia, which is located in the CNS, is one exception. Ganglia function as relay stations, carrying information (to and from the CNS) relating to sensory and involuntary motor function. These structures may be susceptible to damage resulting from injury, infection, and more. Symptoms and treatments may vary depending on the cause of ganglia damage.