Our brains consist of cells which conduct nerve impulses through electrical and chemical signals, these are called neurons. Neurons do not fire at all times; however, that does not mean that inactive neurons are useless, nor that 90% of the 86 billion neurons that make up the human nervous system are permanently inactive.
The enteric nervous system is a subdivision of the autonomic nervous system that directly controls the gastrointestinal system in vertebrates.
The enteric nervous system is embedded in the lining of the gastrointestinal system
The nervous system exerts a profound influence on all digestive processes, namely motility, ion transport associated with secretion and absorption, and gastrointestinal blood flow. Some of this control emanates from connections between the digestive system and central nervous system, but just as importantly, the digestive system is endowed with its own, local nervous system referred to as the enteric or intrinsic nervous system.
The magnitude and complexity of the enteric nervous system is immense – it contains as many neurons as the spinal cord. The enteric nervous system, along with the sympathetic and parasympathetic nervous systems, constitute the autonomic nervous system.
The principal components of the enteric nervous system are two networks or plexuses of neurons, both of which are embedded in the wall of the digestive tract and extend from esophagus to anus:
The myenteric plexus is located between the longitudinal and circular layers of muscle in the tunica muscularis and, appropriately, exerts control primarily over digestive tract motility.
The submucous plexus, as its name implies, is buried in the submucosa. Its principal role is in sensing the environment within the lumen, regulating gastrointestinal blood flow and controlling epithelial cell function. In regions where these functions are minimal, such as the esophagus, the submucous plexus is sparse and may actually be missing in sections.