The enteric nervous system

Summary

This video delves into the autonomic nervous system, focusing on the enteric nervous system (ENS), often referred to as the 'second brain.' The ENS autonomously controls digestion through its two primary plexuses: the myenteric and submucosal plexuses, which regulate motility, secretion, and blood flow. The video also explains how the sympathetic and parasympathetic nervous systems influence gastrointestinal activity, with the sympathetic system inhibiting digestion during stress, while the parasympathetic system enhances digestive processes during rest. The mechanisms of peristalsis, driven by both the ENS and CNS, are also thoroughly explored.

Takeaways

• 😀 The autonomic nervous system consists of three subdivisions: the sympathetic nervous system, parasympathetic nervous system, and enteric nervous system (ENS).
• 😀 The enteric nervous system is sometimes referred to as the 'second brain' because it can function autonomously but also communicates with the central nervous system.
• 😀 The enteric nervous system contains two main networks of neurons: the myenteric plexus and the submucosal plexus, both of which are located in the walls of the gastrointestinal tract.
• 😀 The myenteric plexus controls the motility of the digestive tract, influencing the tone and intensity of muscle contractions in the gastrointestinal system.
• 😀 The submucosal plexus regulates local conditions in the digestive tract, including secretion, blood flow, and absorption, and controls local muscle movements.
• 😀 The ENS can function autonomously through local reflexes, and also communicates with both the sympathetic and parasympathetic nervous systems to regulate gastrointestinal functions.
• 😀 The myenteric plexus is located between the longitudinal and circular layers of muscle in the muscularis externa of the gastrointestinal tract.
• 😀 The submucosal plexus is embedded in the submucosa and controls functions like nutrient absorption and local muscle contractions.
• 😀 Peristalsis in the small intestine is driven by local reflexes within the ENS. These reflexes involve the coordination of sensory neurons, excitatory and inhibitory neurotransmitters, and smooth muscle contractions.
• 😀 The sympathetic nervous system inhibits gastrointestinal activity (such as peristalsis) during stress or fight-or-flight situations, whereas the parasympathetic nervous system stimulates gastrointestinal activity during rest and digestion.

Q & A

What are the three subdivisions of the autonomic nervous system?

The three subdivisions of the autonomic nervous system are the sympathetic nervous system, the parasympathetic nervous system, and the enteric nervous system.

Why is the enteric nervous system often referred to as the 'second brain'?

The enteric nervous system is called the 'second brain' because it is a highly complex system of neurons embedded in the gastrointestinal tract that can function autonomously, though it also communicates with the central nervous system.

What are the two main plexuses of the enteric nervous system?

The two main plexuses of the enteric nervous system are the myenteric plexus (also called Auerbach's plexus) and the submucosal plexus (also called Meissner's plexus).

Where are the myenteric and submucosal plexuses located in the gastrointestinal tract?

The myenteric plexus is located between the longitudinal and circular layers of muscle in the muscularis externa, while the submucosal plexus is located in the submucosa of the gastrointestinal tract.

What is the primary function of the myenteric plexus?

The primary function of the myenteric plexus is to regulate the motility of the gastrointestinal tract, controlling the tone, intensity, and velocity of contractions.

What role does the submucosal plexus play in the gastrointestinal system?

The submucosal plexus is involved in regulating local conditions such as secretion, blood flow, and absorption in the mucosa, as well as controlling local muscle movements.

How does the enteric nervous system regulate peristalsis?

The enteric nervous system regulates peristalsis by using sensory neurons that detect mechanical stretching and chemical composition of food. These neurons activate ascending and descending motor neurons, coordinating muscle contractions and relaxations that propel food along the digestive tract.

How does the sympathetic nervous system affect the enteric nervous system?

The sympathetic nervous system inhibits the enteric nervous system by reducing peristalsis, blood flow, absorption, and local secretion in response to stress or a 'fight or flight' situation.

What is the effect of the parasympathetic nervous system on the enteric nervous system?

The parasympathetic nervous system stimulates the enteric nervous system, enhancing peristalsis, blood flow, absorption, and local secretion in the digestive tract, promoting digestion and nutrient absorption.

Can the enteric nervous system function independently of the central nervous system?

Yes, the enteric nervous system can function autonomously using local reflexes. However, it also communicates with the central nervous system through the sympathetic and parasympathetic pathways to modulate its activity.