Nerve ganglion: types and functions of this part of the nervous system

A nerve ganglion is the grouping of neuronal bodies that are located outside the central nervous system and that performs very important functions to transport electrical impulses connecting the brain with organs specific.

In this article we will see what a nerve ganglion is, how it is composed and what are the two main types in which it is divided.

• Related article: "Parts of the Nervous System: anatomical structures and functions"

What is a nerve ganglion?

In biology, the term "ganglion" is used to designate the masses of tissue that form in cellular systems. Specifically in neurology, this term usually refers to a mass or grouping of nerve cell bodies present in most living organisms. Its main function is to carry nerve impulses from the periphery to the center, or vice versa.

In this sense, a "nerve ganglion" is the agglomeration of neuronal bodies or bodies that are located in the autonomic nervous system. It is mainly responsible for connecting the peripheral nervous system with the central nervous system, both in an efferent sense (from the central nervous system to the sensory organs) as afferent (from the sensory organs to the nervous system central).

Therefore, a nerve ganglion is broadly composed of Afferent nerve cell bodies, efferent nerve cell bodies, and neural axons. Likewise, it can be divided into two large subtypes according to the specific function they fulfill within the peripheral nervous system.

• You may be interested: "Neuronal soma or perikaryon: parts and functions"

Types of nerve ganglion

Nerve ganglia are located outside the central nervous system, that is, in the autonomic nervous system. According to the specific part of the autonomic nervous system to which they belong, as well as according to the specific path that they follow to transmit nerve impulses, these ganglia can be divided into sensory and autonomic.

1. Sensory or spinal nerve ganglion

The sensory nerve ganglion acts by receiving signals from the periphery and sending them to the brain, that is, it has an afferent function. It is also known as the somatic ganglion, sensory ganglion, or spinal ganglion, since it is located in the back of other structures called spinal nerves. The latter are the nerves that form the dorsal and ventral roots of the spinal cord. For the same reason, the sensory nerve ganglion is also known as the spinal ganglion.

It is prolonged by these roots or branches, crossing different parts of the body, and is responsible for activating electrical impulses from the skin and the muscles of the back (dorsal branches). In fact, another common name for these ganglia is "dorsal root ganglia."

2. Autonomic or vegetative nerve ganglion

The autonomic nervous ganglion acts in the opposite direction to the sensory nerve ganglion, that is, in an efferent way: it receives signals from the central nervous system and sends them to the periphery. It is also called the vegetative ganglion, and as it belongs to the autonomic nervous system, what it does is regulate motor activity. They are located near the viscera on which it acts, although keeping distance with these, and they are divided in turn into two types of ganglia:

2.1. Parasympathetic ganglia

These are the ganglia that are part of the parasympathetic nervous system. They are located in the wall of the innervating viscera, that is, in the specific area of ​​the body where the nerve acts. Due to the closeness that they keep with the organs on which they act, are also known as intramular ganglia (except for those that act on the neck and head). They are made up of three different roots depending on the path that the nerve fibers follow: motor root, sympathetic root or sensory root.

In turn, these nerve fibers make up different cranial nerves, including the oculomotor, the facial, the glossopharyngeal, the vagus, and the pelvic splanchnic.

2.2. Sympathetic ganglia

As their name implies, they are part of the sympathetic nervous system. They are found on both sides of the spinal cord, forming long nerve chains. It is the nodes that are found around the celiac trunk (arterial trunk that originates in the aorta, specifically in the part of the abdomen of this artery). The latter are the prevertebral sympathetic ganglia, and they can innervate the organs that make up the abdominal and pelvic region, or else.

On the other hand, there are the paravertebral ganglia, which form the paravertebral chain and run from the neck towards the thoracic cavity, acting especially on the viscera.

Among its main functions is the transmission of information on events that may be risky for the body. In this sense, they are related to stressful situations and constitute one of the elements responsible for responding to them, either through flight or through aggression.

Bibliographic references:

• University of Navarra Clinic (2015) Nervous Ganglion. Medical Dictionary, University of Navarra. Retrieved August 20, 2018.
• Encyclopedia Britannica (2018). Ganglion Physiology, British Encyclopedia. Retrieved August 20, 2018. Available in https://www.britannica.com/science/ganglion.
• Butler, D. (2002). Mobilization of the nervous system. Editorial Paidotribo: Barcelona.
• Navarro, X. (2002) Physiology of the autonomic nervous system. Neurology Journal, 35 (6): 553-562.