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Metasympathetic Nervous System

For medical students2 min readUpdated 2026-10-10

The metasympathetic nervous system (MNS) is an intramural division of the autonomic nervous system responsible for the independent rhythmic motor activity of hollow visceral organs. It consists of a network of isolated microganglia located within the walls of these organs.

LocationWalls of hollow visceral organs with intrinsic motor activity
Structural BasisMicroganglia containing afferent, interneurons, and efferent neurons
NeurochemistryATP, adenosine, acetylcholine, norepinephrine, serotonin, histamine
AutonomyThe most independent division of the ANS from the central nervous system

Distribution and Concept of Automatism

The metasympathetic division is localized exclusively within the walls of hollow internal organs. A key prerequisite for the presence of a metasympathetic network is the organ's capacity for automatism. Automatism refers to the ability of an organ to contract rhythmically, maintaining a set frequency and amplitude without external neural input. The microganglion formations of the MNS serve as the structural substrate for this property.

The MNS innervates only organs possessing motor activity. The main regions include:

Additionally, the system innervates the bronchi, uterus, urinary bladder, gallbladder, and biliary tract.

Morphology and Structure of Microganglia

Structurally, the system is a complex of microganglia. In their internal organization, they closely resemble the nuclear formations of the central nervous system.

Features of tissue organization:

Three types of neurons are located within the microganglia: afferent (sensory), interneurons, and efferent (motor). These neurons feature a generator of spontaneous impulse activity. Their cell bodies are densely covered with synapses, and their processes store a vast number of vesicles containing various neurotransmitters.

Interaction with the ANS and Neurochemistry

The metasympathetic system exhibits the highest degree of autonomy: its activity is minimally dependent on the central nervous system compared to the classical sympathetic and parasympathetic divisions, though it is not in an antagonistic relationship with them.

The MNS receives inputs from both the sympathetic and parasympathetic divisions, and ganglionic neurons possess receptors for acetylcholine and norepinephrine.

Features of neurotransmitter systems:

  1. Purinergic transmission: Neurons secrete ATP and adenosine. Their primary physiological role is to mediate inhibitory influences that oppose excitatory signals. For example, activation of purinergic neurons leads to a decrease in the tone of the stomach and intestines.
  2. Postganglionic neurotransmitters: A wide spectrum of biologically active substances is released in synapses: in addition to acetylcholine and norepinephrine, serotonin, dopamine, adrenaline, histamine, and others are actively utilized.

Mnemonic

To remember organs with metasympathetic innervation, use the rule of "hollow motor tubes and pouches": heart, bronchi, GI tract, uterus, gallbladder, and urinary bladder. If a hollow organ can contract rhythmically on its own, it features the MNS.

Frequently asked questions

What Dogiel cell types form the morphological basis of intramural MNS ganglia?

The morphological basis of intramural ganglia is formed by three functional types of neurons classified according to Dogiel:

  • Sensory neurons (Type II cells) — multipolar cells whose dendrites form receptors in the organ tissue.
  • Associative neurons (Type III cells) — interneurons that receive signals from sensory neurons and transmit them to effector neurons of the same or neighboring ganglia.
  • Effector neurons (Type I cells) — long-process cells representing the final link in impulse transmission to the working tissue ("common final path").
What local reflex arcs are closed at the level of the metasympathetic nervous system?

Local reflex arcs comprising sensory, associative, and effector neurons are closed at the level of the metasympathetic nervous system.

The primary pathway of signal transmission: sensory neurons transmit signals to associative cells, most often within the same ganglion; axons of associative neurons project to effector neurons of the same or adjacent ganglia.

An alternative, debated pathway:

  • Two-neuron peripheral reflex arc — direct signal transmission from sensory neurons to effector neurons.
What is automatism in the context of the metasympathetic nervous system?

It is the ability of an organ to contract rhythmically at a specific frequency and amplitude without external commands. This property is entirely determined by the activity of the MNS microganglion formations.

Is the metasympathetic system an antagonist of the sympathetic system?

No, the MNS is not in an antagonistic relationship with other divisions. It receives input signals from them and possesses receptors for both norepinephrine and acetylcholine.

What is the result of purinergic neuron activation?

Purinergic transmission (via ATP and adenosine) exerts inhibitory influences. In practice, this manifests, for instance, as a reduction in the muscle tone of the stomach and intestines.

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