20 - Enteric Nervous System (ENS) Overview

Vocabulary flashcards covering the enteric nervous system (structure, plexuses, neuron types, reflexes, CNS integration, and related diseases) as presented in the lecture notes.

Enteric Nervous System (ENS)

The 3rd division of the autonomic nervous system; intrinsic innervation of the GI tract, consisting of about 80–100 million neurons.

Intrinsic innervation

The network of neurons within the GI tract that provides local, autonomous control of GI function.

Meissner’s plexus (Submucosal plexus)

Plexus located in the submucosa that mainly regulates secretion and local blood flow.

Auerbach’s plexus (Myenteric plexus)

Plexus between the circular and longitudinal muscle layers that mainly controls GI motility.

Submucosa

Connective tissue layer beneath the mucosa containing blood vessels and Meissner’s plexus.

Mucosa

Innermost lining of the GI tract involved in secretion and absorption.

Longitudinal muscle

Muscle layer running lengthwise along the GI tract; part of the muscularis externa.

Circular muscle

Muscle layer wrapping around the GI tract; contracts to narrow the lumen.

Afferent (sensory) neurons

ENS neurons that detect luminal contents or stretch and relay information to other neurons.

Interneurons

ENS neurons that process and relay signals within the enteric circuitry.

Efferent (secretomotor) neurons

ENS neurons that stimulate secretory activity and modulate motility.

Excitatory neurotransmitters

Neurotransmitters that promote contraction or secretion in the GI tract.

Inhibitory neurotransmitters

Neurotransmitters that promote relaxation or reduce secretion in the GI tract.

Motility

Movement of the GI tract (peristalsis, segmentation) controlled by the ENS.

Secretory reflex

Reflex mediated by the submucosal plexus that regulates secretion and local blood flow.

Motor reflex

Reflex mediated by the myenteric plexus that controls GI motility.

Blood flow regulation by ENS

ENS influences regional blood flow to the GI tract through the submucosal reflexes.

CNS-ENS integration

Bidirectional communication between the CNS and ENS; CNS influence varies along the GI tract.

Hirschsprung’s disease

Congenital absence of ENS neurons leading to halted peristalsis in the affected segment and loss of rectoanal reflex.

Chaga’s (Chagas) disease

Infection with Trypanosoma cruzi causing ENS degeneration and GI motility disorders (e.g., megaesophagus).

Achalasia

Esophageal motility disorder due to impaired relaxation of the lower esophageal sphincter from neural dysfunction.

Parkinson’s disease

Neurological disorder associated with GI dysmotility and potential ENS involvement.

Irritable bowel syndrome (IBS)

Functional GI disorder that may involve ENS neurotransmission and altered motility.

Endogenous opioids and receptors

Opioid peptides produced in the ENS and their receptors that modulate neurotransmission and GI motility.