Ganglion

Ganglion

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Encyclopedia
In anatomy
Anatomy
Anatomy is a branch of biology and medicine that is the consideration of the structure of living things. It is a general term that includes human anatomy, animal anatomy , and plant anatomy...

, a ganglion (icon ; plural ganglia) is a biological tissue
Biological tissue
Tissue is a cellular organizational level intermediate between cells and a complete organism. A tissue is an ensemble of cells, not necessarily identical, but from the same origin, that together carry out a specific function. These are called tissues because of their identical functioning...

 mass, most commonly a mass of nerve cell
Neuron
A neuron is an electrically excitable cell that processes and transmits information by electrical and chemical signaling. Chemical signaling occurs via synapses, specialized connections with other cells. Neurons connect to each other to form networks. Neurons are the core components of the nervous...

 bodies. Cells found in a ganglion are called ganglion cell
Ganglion cell
A retinal ganglion cell is a type of neuron located near the inner surface of the retina of the eye. It receives visual information from photoreceptors via two intermediate neuron types: bipolar cells and amacrine cells...

s, though this term is also sometimes used to refer specifically to retinal ganglion cells.

A less common usage of ganglion is ganglion cyst
Ganglion cyst
A ganglion cyst, also known as a bible cyst, is a swelling that often appears on or around joints and tendons in the hand or foot. The size of the ganglion or cyst can vary over time. It is most frequently located around the dorsum of the wrist and on the fingers...

, a small lump most commonly on the hand or foot, not believed to be of nerve cells.

Neurology


In neurological contexts, ganglia are composed mainly of somata
Soma (biology)
The soma , or perikaryon , or cyton, is the bulbous end of a neuron, containing the cell nucleus. The word "soma" comes from the Greek σῶμα, meaning "body"; the soma of a neuron is often called the "cell body"...

 and dendritic structures
Dendrite
Dendrites are the branched projections of a neuron that act to conduct the electrochemical stimulation received from other neural cells to the cell body, or soma, of the neuron from which the dendrites project...

 which are bundled or connected together. Ganglia often interconnect with other ganglia to form a complex system of ganglia known as a plexus
Plexus
A plexus is a part of nervous system. Plexus has a slightly different definition in vertebrates and in invertebrates.- In vertebrates :In vertebrates, a plexus is an area where nerves branch and rejoin. The electrical signals do not mix; rather, the fibres travel together with their electrical...

. Ganglia provide relay points and intermediary connections between different neurological structures in the body, such as the peripheral
Peripheral nervous system
The peripheral nervous system consists of the nerves and ganglia outside of the brain and spinal cord. The main function of the PNS is to connect the central nervous system to the limbs and organs. Unlike the CNS, the PNS is not protected by the bone of spine and skull, or by the blood–brain...

 and central
Central nervous system
The central nervous system is the part of the nervous system that integrates the information that it receives from, and coordinates the activity of, all parts of the bodies of bilaterian animals—that is, all multicellular animals except sponges and radially symmetric animals such as jellyfish...

 nervous systems.

There are two major groups of ganglia:
  • Dorsal root ganglia
    Dorsal root ganglion
    In anatomy and neuroscience, a dorsal root ganglion is a nodule on a dorsal root that contains cell bodies of neurons in afferent spinal nerves.-Unique unipolar structure:...

     (also known as the spinal ganglia) contain the cell bodies of sensory (afferent)
    Afferent nerve
    In the nervous system, afferent neurons , carry nerve impulses from receptors or sense organs towards the central nervous system. This term can also be used to describe relative connections between structures. Afferent neurons communicate with specialized interneurons...

     nerve
    Nerve
    A peripheral nerve, or simply nerve, is an enclosed, cable-like bundle of peripheral axons . A nerve provides a common pathway for the electrochemical nerve impulses that are transmitted along each of the axons. Nerves are found only in the peripheral nervous system...

    s.
  • Autonomic ganglia
    Autonomic ganglion
    Autonomic ganglia are clusters of neuronal cell bodies and their dendrites and are essentially a junction between autonomic nerves originating from the central nervous system and autonomic nerves innervating their target organs in the periphery....

     contain the cell bodies of autonomic
    Autonomic nervous system
    The autonomic nervous system is the part of the peripheral nervous system that acts as a control system functioning largely below the level of consciousness, and controls visceral functions. The ANS affects heart rate, digestion, respiration rate, salivation, perspiration, diameter of the pupils,...

     nerves.


In the autonomic nervous system, fibers from the central nervous system
Central nervous system
The central nervous system is the part of the nervous system that integrates the information that it receives from, and coordinates the activity of, all parts of the bodies of bilaterian animals—that is, all multicellular animals except sponges and radially symmetric animals such as jellyfish...

 to the ganglia are known as preganglionic fibers
Preganglionic fibers
In the autonomic nervous system, fibers from the CNS to the ganglion are known as preganglionic fibers.All preganglionic fibers, whether they are in the sympathetic division or in the parasympathetic division, are cholinergic .Sympathetic preganglionic fibers tend to be shorter than parasympathetic...

, while those from the ganglia to the effector organ are called postganglionic fibers
Postganglionic fibers
In the autonomic nervous system, fibers from the ganglion to the effector organ are called postganglionic fibers.-Neurotransmitters:The neurotransmitters used for postganglionic fibers differ:...

.

Basal ganglia


The term "ganglion" usually refers to the peripheral nervous system
Peripheral nervous system
The peripheral nervous system consists of the nerves and ganglia outside of the brain and spinal cord. The main function of the PNS is to connect the central nervous system to the limbs and organs. Unlike the CNS, the PNS is not protected by the bone of spine and skull, or by the blood–brain...

.

However, in the brain (part of the central nervous system
Central nervous system
The central nervous system is the part of the nervous system that integrates the information that it receives from, and coordinates the activity of, all parts of the bodies of bilaterian animals—that is, all multicellular animals except sponges and radially symmetric animals such as jellyfish...

), the "basal ganglia
Basal ganglia
The basal ganglia are a group of nuclei of varied origin in the brains of vertebrates that act as a cohesive functional unit. They are situated at the base of the forebrain and are strongly connected with the cerebral cortex, thalamus and other brain areas...

" is a group of nuclei interconnected with the cerebral cortex
Cerebral cortex
The cerebral cortex is a sheet of neural tissue that is outermost to the cerebrum of the mammalian brain. It plays a key role in memory, attention, perceptual awareness, thought, language, and consciousness. It is constituted of up to six horizontal layers, each of which has a different...

, thalamus
Thalamus
The thalamus is a midline paired symmetrical structure within the brains of vertebrates, including humans. It is situated between the cerebral cortex and midbrain, both in terms of location and neurological connections...

 and brainstem, associated with a variety of functions: motor control, cognition, emotions, and learning.

Partly due to this ambiguity, the Terminologia Anatomica
Terminologia Anatomica
Terminologia Anatomica is the international standard on human anatomic terminology. It was developed by the Federative Committee on Anatomical Terminology and the International Federation of Associations of Anatomists and was released in 1998. It supersedes the previous standard, Nomina...

recommends using the term basal nuclei instead of basal ganglia.