FARMACOLOGIA do Sistema Nervoso Autônomo #4⎟Efeitos sobre o Sistema GASTROINTESTINAL

Summary

This educational video explains how the autonomic nervous system controls the gastrointestinal system, focusing on the parasympathetic and sympathetic branches. The parasympathetic system, activated during relaxation, enhances digestion and absorption by increasing motility and stimulating secretions like saliva and gastric acid. It also plays a role in conditions such as ileus and congenital megacolon. The video discusses muscarinic agonists and antagonists used to treat gastrointestinal disorders and highlights the effects of adrenergic receptors on digestion. The viewer gains insights into how these systems and medications influence gastrointestinal function, with real-world applications in therapeutic management.

Takeaways

• 😀 The autonomic nervous system (ANS) plays a crucial role in regulating the gastrointestinal (GI) system, specifically through the enteric nervous system and connections with sympathetic and parasympathetic fibers.
• 😀 The parasympathetic nervous system is active during relaxation and digestion, promoting nutrient absorption and energy storage by stimulating GI motility and secretions.
• 😀 Acetylcholine, released by parasympathetic neurons, acts on muscarinic receptors in smooth muscle and glands to stimulate digestion, including increased gastric acid secretion and saliva production.
• 😀 The vagus and pelvic nerves carry parasympathetic signals to the GI tract, activating excitatory and inhibitory motor neurons to enhance peristalsis and reduce sphincter tension.
• 😀 Excessive parasympathetic activity can lead to increased peristalsis, slow intestinal transit, and even cause abdominal cramps.
• 😀 In addition to controlling motility, the parasympathetic system also regulates gastric acid secretion, which is essential for digestion, alongside other factors like histamine and gastrin.
• 😀 Medications that act as muscarinic agonists can be used to treat certain GI disorders, such as post-operative ileus and congenital megacolon, by enhancing peristalsis when there is no obstruction.
• 😀 Muscarinic antagonists (antimuscarinics) can reduce GI motility and secretions, making them useful in conditions like medication-induced diarrhea or to relieve abdominal cramps.
• 😀 Antimuscarinic drugs, such as atropine and scopolamine, can also block the secretion of gastric acid and cause dry mouth by inhibiting saliva production.
• 😀 Although antimuscarinic drugs can temporarily slow GI motility, other local mechanisms in the enteric nervous system can help restore peristalsis.
• 😀 Sympathetic receptors, particularly adrenergic receptors, can also influence the GI system. They can reduce peristalsis, cause constipation, and affect salivation, leading to dry mouth in certain medications.
• 😀 Understanding the role of the parasympathetic and sympathetic systems is essential for effective pharmacological management of GI disorders, helping healthcare professionals guide patients and optimize treatment.

Q & A

How does the autonomic nervous system control the gastrointestinal system?

The autonomic nervous system controls the gastrointestinal system through the enteric nervous system, which includes sensory fibers that respond to the presence of food in the gastrointestinal tract, and sympathetic and parasympathetic fibers originating from the brain. These components communicate with secretory cells to release digestive peptides and affect muscle activity, altering motility.

What role does the parasympathetic system play in gastrointestinal function?

The parasympathetic system is activated during relaxation and digestion, increasing gastrointestinal motility. It stimulates the release of acetylcholine, which activates muscarinic receptors on smooth muscles and secretory glands, aiding in processes like peristalsis, acid secretion, and saliva production.

How does acetylcholine affect the gastrointestinal tract?

Acetylcholine activates muscarinic M3 receptors on smooth muscles in the gastrointestinal tract, leading to depolarization and calcium influx, which promotes peristaltic movements. It also stimulates acid secretion in the stomach and saliva production.

What are the potential effects of increased parasympathetic activity on the gastrointestinal system?

Increased parasympathetic activity can enhance peristalsis, slow down intestinal transit, and even cause cramps. It can also lead to excessive secretion of gastric acid and saliva.

What are some clinical uses of muscarinic agonists?

Muscarinic agonists are used to treat conditions where there is reduced smooth muscle activity in the gastrointestinal tract, such as postoperative ileus or congenital megacolon. They help stimulate peristalsis and alleviate issues related to slow gut movement.

What are the risks associated with using muscarinic agonists in certain gastrointestinal conditions?

Muscarinic agonists must be used cautiously, as they can worsen gastrointestinal obstruction. It is essential to rule out any blockages before using these drugs, as they could exacerbate the problem and even lead to perforation due to increased pressure.

What are the effects of muscarinic antagonists on gastrointestinal motility?

Muscarinic antagonists, or antimuscarinics, block muscarinic receptors, inhibiting gastrointestinal motility. This results in reduced peristaltic contractions, slower gastric emptying, and extended intestinal transit time, which may lead to constipation.

How can muscarinic antagonists be used in the treatment of diarrhea?

Muscarinic antagonists can be used to treat medication-induced diarrhea by reducing peristalsis and slowing intestinal transit. However, this is typically only effective when the diarrhea is caused by muscarinic agonists.

What side effects are associated with antimuscarinic drugs?

Antimuscarinic drugs can cause dry mouth due to reduced saliva secretion, blurred vision due to impaired eye accommodation, and decreased gastrointestinal motility, potentially leading to constipation.

How does the sympathetic nervous system affect the gastrointestinal tract?

Although there are no specific sympathomimetic or sympatholytic drugs for the gastrointestinal system, the sympathetic nervous system affects gastrointestinal motility. Activation of adrenergic receptors in the smooth muscles can reduce peristalsis and cause gastrointestinal discomfort, especially during stress.