Autonomic Regulation of Digestion (Enteric Plexuses)

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Anatomy and Regulation
digestive system
Systems Biology

Systems Biology

The enteric nervous system (ENS) is a branch of the autonomic nervous system and consists of two neural plexuses, the submucosal plexus and the myenteric plexus. The submucosal plexus is primarily responsible for controlling digestive secretions and absorption, while the myenteric plexus controls gastrointestinal (GI) tract motility. The enteric nervous system can directly respond to the presence of food, but it also communicates with the parasympathetic and sympathetic divisions of the autonomic nervous system.

The parasympathetic nervous system sends signals to the enteric nervous system via the vagus nerve, increasing digestive activities. These activities include increased peristalsis, increased blood flow to digestive organs, increased digestive secretions, and decreased release of glucose from the liver. In contrast, the sympathetic nervous system has the opposite effect on digestion: it reduces digestive activity by decreasing peristalsis, blood flow to digestive organs, secretion, and increasing glucose release from the liver.

Lesson Outline

<ul> <li>The Enteric Nervous System <ul> <li>Two neural plexuses: submucosal plexus and myenteric plexus</li> </ul> </li> <li>Submucosal Plexus <ul> <li>Located between the mucosa and circular muscle</li> <li>Functions: triggers local secretion of digestive substances and vasodilation of local blood vessels</li> </ul> </li> <li>Myenteric Plexus <ul> <li>Located between the circular and longitudinal muscle layers of the digestive tract</li> <li>Function: controls GI tract motility through peristalsis</li> </ul> </li> <li>Direct Response to Food Presence <ul> <li>Both plexuses can directly respond to food presence and control digestion</li> </ul> </li> <li>Interaction with Central Nervous System (CNS) <ul> <li>Enteric nervous system can receive signals from CNS through parasympathetic and sympathetic nervous systems</li> </ul> </li> <li>Parasympathetic Nervous System <ul> <li>Stimulates the enteric nervous system via the vagus nerve</li> <li>Increases digestive functions: peristalsis, blood flow, digestive secretions, and decreases glucose production in the liver</li> </ul> </li> <li>Sympathetic Nervous System <ul> <li>Decreases digestion in response to perceived stress</li> <li>Reduces digestive functions: peristalsis, blood flow, digestive secretion, and increases glucose mobilization from the liver</li> </ul> </li> </ul>

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FAQs

What are the roles of the enteric plexuses in autonomic regulation of digestion?

The enteric plexuses, specifically the myenteric and submucosal plexuses, are essential components of the enteric nervous system and play critical roles in the autonomic regulation of digestion. The myenteric plexus is responsible for regulating gastrointestinal motility and coordinating peristalsis, whereas the submucosal plexus controls mucosal function, such as secretion and absorption, and helps regulate local blood flow in the gastrointestinal tract.

How do the parasympathetic and sympathetic nervous systems interact with the enteric nervous system to regulate digestion?

The parasympathetic and sympathetic nervous systems interact with the enteric nervous system to regulate digestion primarily through modulation of the activity of the enteric plexuses. The parasympathetic nervous system, mainly through the vagus nerve, stimulates the enteric nervous system, promoting gastrointestinal motility, secretion, and absorption. In contrast, the sympathetic nervous system acts to inhibit the enteric nervous system, thus reducing gastrointestinal motility, secretion, and blood flow. This delicate balance between the parasympathetic and sympathetic systems helps maintain proper digestive function.

How does the vagus nerve influence digestion?

The vagus nerve, a component of the parasympathetic nervous system, has a significant influence on digestion by directly and indirectly stimulating the enteric nervous system. Via preganglionic fibers, the vagus nerve releases acetylcholine, which activates the release of additional neurotransmitters within the enteric plexuses. This action leads to the promotion of gastrointestinal motility, increased secretion of digestive enzymes and hormones, and improved absorption of nutrients.

What is the role of peristalsis in the autonomic regulation of digestion?

Peristalsis is the coordinated, rhythmic contraction and relaxation of gastrointestinal smooth muscles that facilitates the propulsion of food and waste through the digestive tract. It is primarily regulated by the enteric nervous system, specifically the myenteric plexus. The autonomic nervous system, through the parasympathetic and sympathetic branches, modulates peristalsis by either promoting or inhibiting the activity of the myenteric plexus, respectively. This regulation ensures the efficient processing and transport of food and waste within the digestive system.

What is the functional difference between the myenteric and submucosal plexuses?

Though both myenteric and submucosal plexuses are essential components of the enteric nervous system involved in the autonomic regulation of digestion, they serve distinct functions. The myenteric plexus, located between the longitudinal and circular muscle layers of the gastrointestinal tract, is primarily responsible for regulating gastrointestinal motility, including peristalsis and coordination of smooth muscle contractions. On the other hand, the submucosal plexus, situated in the submucosa of the gastrointestinal wall, oversees mucosal functions such as glandular secretion and absorption, as well as the regulation of local blood flow.