What happens if enteric nervous system or second brain is absent
Answers
Answer:
The enteric nervous system (ENS) is large, complex and uniquely able to orchestrate gastrointestinal behaviour independently of the central nervous system (CNS). An intact ENS is essential for life and ENS dysfunction is often linked to digestive disorders. The part the ENS plays in neurological disorders, as a portal or participant, has also become increasingly evident. ENS structure and neurochemistry resemble that of the CNS, therefore pathogenic mechanisms that give rise to CNS disorders might also lead to ENS dysfunction, and nerves that interconnect the ENS and CNS can be conduits for disease spread. We review evidence for ENS dysfunction in the aetiopathogenesis of autism spectrum disorder, amyotrophic lateral sclerosis, transmissible spongiform encephalopathies, Parkinson disease and Alzheimer disease. Animal models suggest that common pathophysiological mechanisms account for the frequency of gastrointestinal comorbidity in these conditions. Moreover, the neurotropic pathogen, varicella zoster virus (VZV), unexpectedly establishes latency in enteric and other autonomic neurons that do not innervate skin. VZV reactivation in these neurons produces no rash and is therefore a clandestine cause of gastrointestinal disease, meningitis and strokes. The gut–brain alliance has raised consciousness as a contributor to health, but a gut–brain axis that contributes to disease merits equal attention.
The gut is a complicated organ1. A byzantine array of events is required for digestion and absorption to be successful. Muscular sphincters compartmentalize the bowel, dividing it into functionally distinct regions with radically different luminal environments. Neuronal monitoring of luminal contents permits ingested material to be transported aborally at a rate that allows each compartment to accomplish its task2. Contractions by smooth muscle (along the entire gastrointestinal tract) and skeletal muscle (in the oesophagus and anus) are thus choreographed into activity patterns, such as churning (in the stomach), segmentation (in the small intestine), or haustration (in the colon) that grind, mix, or temporarily hold luminal contents, in addition to providing aboral power propulsion and retropulsion2. Secretory mechanisms maintain a regionally appropriate pH as well as tightly regulated concentrations of electrolytes, enzymes and mucus. A thin semipermeable epithelial barrier, which is continuously regenerated from gastrointestinal stem cells3, separates the lumen from the body’s internal milieu. This barrier facilitates absorption, but also prevents the leakage of essential molecules into the intestinal lumen as well as the translocation of digestive enzymes, toxins and gut microbiota into the body from the lumen4. A scaffold of loose connective tissue, which contains the body’s largest array of immune effector cells, provides mechanical and defensive support for the barrier5. All of these functions — secretion, motility, mucosal maintenance and immunological defence — require an exquisite degree of regulation and coordination, which the enteric nervous system (ENS) provides