What specific neurotransmitters do the axons of sympathetic effector cells release at target organs?

At target organs, the axons of sympathetic effector neurons form adrenergic (sympathetic neuroeffector) synapses. Norepinephrine is the primary neurotransmitter in these synapses. In adrenergic synapses, the mechanism of action of norepinephrine is metabotropic; the tissue response depends on the predominant receptor type: α1 and β1 are excitatory, while α2 and β2 are inhibitory.

From which embryonic source do sympathetic ganglion neurons develop?

Sympathetic ganglion neurons develop from the neural crest (often referred to in literature as neural crest derivatives or ganglionic plates). Neuroblasts (sympathoblasts) delaminate from this common pool of sympathetic precursors. Adrenal medulla cells also originate from the neural crest and function as modified postganglionic sympathetic neurons.

How does the cellular arrangement in a sympathetic ganglion differ from a sensory spinal ganglion?

In a sympathetic ganglion, neuronal cell bodies are arranged diffusely (scattered throughout the stroma), whereas in a sensory spinal ganglion, they form organized groups along the periphery of the organ.

What type of synapses are formed on the dendrites of effector neurons?

Preganglionic myelinated fibers form cholinergic synapses on the bodies and dendrites of effector neurons.

Can SIF cells be visualized using standard hematoxylin and eosin staining?

No, these small, intensely fluorescent cells are indistinguishable on standard histological preparations.

What is divergence in a sympathetic ganglion?

It is impulse multiplication, where a single preganglionic neuron transmits a signal via axon collaterals to multiple (up to 100) effector neurons simultaneously.

Home › Histology › Sympathetic Ganglion: Anatomy and Histology

Sympathetic Ganglion

*Ganglion sympathicum*

For medical students2 min readUpdated 2026-10-10

A sympathetic ganglion is a peripheral autonomic ganglion where signal transmission from the central nervous system to visceral organs takes place. The primary function of the ganglion is the distribution and modulation of nerve impulses through multipolar neurons.

ArchitectonicsDiffuse arrangement of neuronal cell bodies without strict ordering

Neuronal sheathsThe cell is surrounded by glia, a basement membrane, and connective tissue

Principal cellsMultipolar effector neurons with short dendrites

Inhibitory cellsSIF cells limit excessive sympathetic response

General Organization and Localization

Sympathetic ganglia are located within the sympathetic trunk and also form large autonomic plexuses in the abdominal cavity (the most prominent being the celiac plexus).

Externally, each ganglion is covered by a dense connective tissue capsule. Connective tissue septa extend inward from this outer capsule to form the stroma. A key histological feature of the sympathetic ganglion is the diffuse arrangement of neurons. Unlike sensory ganglia of spinal nerves, where cells lie in distinct groups, here nerve cell bodies are randomly scattered among the elements of the connective tissue stroma.

The cellular composition of the ganglion is represented by two main populations: dominant effector neurons and an additional specialized type—SIF cells.

Characteristics of Effector Neurons

The bulk of the cells in the ganglion consist of effector neurons. According to morphological classification, they are multipolar cells: many short branching dendrites and only one long axon extend from their cell body.

The body of each effector neuron is protected by three successive sheaths:

Satellite glial cells (mantle gliocytes) — they are located closest to the perikaryon and are easily identified by small rounded nuclei.
Basement membrane.
Thin connective tissue sheath — the outer layer, which is practically invisible on standard histological preparations.

Preganglionic myelinated fibers approach the ganglion from the spinal cord. They form cholinergic synapses on the bodies and dendrites of effector neurons. In turn, the axons of the effector cells leave the ganglion, travel toward the target organ, and form adrenergic synapses there.

Neuronal Connections: Divergence and Convergence

A sympathetic ganglion is not merely a relay station, but a complex distribution center. It is characterized by two important neurophysiological phenomena:

Divergence (impulse multiplication): Due to branching (collaterals) of its axon, a single preganglionic neuron can simultaneously contact multiple effector neurons. The number of such contacts can reach up to one hundred, ensuring widespread signal dissemination.
Convergence: The reverse process, in which branches from several completely different preganglionic fibers converge and form synapses on a single effector neuron.

SIF Cells: Built-in Limiters

Of special interest is the additional population of SIF cells, which stands for Small Intensely Fluorescent cells. On routine stained microscope slides, they cannot be discerned; special visualization techniques are required.

Functionally, SIF cells act as interneurons with an inhibitory role. They are excited by incoming preganglionic fibers, but their main task is to inhibit the further transmission of the nerve impulse to the effector neurons. This provides signal modulation: SIF cells limit the sympathetic response, preventing it from becoming excessive.

Mnemonic

Remember the three "D"s for the sympathetic ganglion: Diffuse cell arrangement, Long axons (and short dendrites), and Divergence of impulses.

Frequently asked questions

What specific neurotransmitters do the axons of sympathetic effector cells release at target organs?: At target organs, the axons of sympathetic effector neurons form adrenergic (sympathetic neuroeffector) synapses. Norepinephrine is the primary neurotransmitter in these synapses. In adrenergic synapses, the mechanism of action of norepinephrine is metabotropic; the tissue response depends on the predominant receptor type: α1 and β1 are excitatory, while α2 and β2 are inhibitory.
From which embryonic source do sympathetic ganglion neurons develop?: Sympathetic ganglion neurons develop from the neural crest (often referred to in literature as neural crest derivatives or ganglionic plates). Neuroblasts (sympathoblasts) delaminate from this common pool of sympathetic precursors. Adrenal medulla cells also originate from the neural crest and function as modified postganglionic sympathetic neurons.
How does the cellular arrangement in a sympathetic ganglion differ from a sensory spinal ganglion?: In a sympathetic ganglion, neuronal cell bodies are arranged diffusely (scattered throughout the stroma), whereas in a sensory spinal ganglion, they form organized groups along the periphery of the organ.
What type of synapses are formed on the dendrites of effector neurons?: Preganglionic myelinated fibers form cholinergic synapses on the bodies and dendrites of effector neurons.
Can SIF cells be visualized using standard hematoxylin and eosin staining?: No, these small, intensely fluorescent cells are indistinguishable on standard histological preparations.
What is divergence in a sympathetic ganglion?: It is impulse multiplication, where a single preganglionic neuron transmits a signal via axon collaterals to multiple (up to 100) effector neurons simultaneously.

Go deeper

Morphology and ultrastructure of satellite glial cells
Specific methods for identifying SIF cells in tissue
Mechanisms of adrenergic synapse formation
Topography and structure of the celiac plexus
Histochemistry of autonomic cholinergic synapses