What is the function of the Myenteric plexus?
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It primarily controls gastrointestinal motility.
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What is the function of the Myenteric plexus?
It primarily controls gastrointestinal motility.
What is the third phase of digestion?
Intestinal phase, where food is in the intestines.
How do digestive reflexes contribute to the digestive process?
They regulate motility, secretion, and blood flow in the gastrointestinal tract.
What triggers digestive reflexes?
The presence of food in the gastrointestinal tract.
What is absorption in the GIT?
The movement of nutrients, water, and electrolytes from the lumen of the GIT into the bloodstream.
What coordinates the gastric phase?
Local endocrine cells and the enteric nervous system (ENS).
Can digestive reflexes be influenced by the central nervous system?
Yes, they can be modulated by signals from the central nervous system.
At what age did the boy first pass meconium?
On day 5.
What is the effect of the sympathetic nervous system on the digestive system?
Inhibitory.
What is the first phase of digestion after a meal?
Cephalic phase, involving anticipation, sight, smell, and taste of food.
Where are short reflexes integrated in the GIT?
In the Enteric Nervous System (ENS).
What stimulates the release of Secretin?
H+ in the lumen of the duodenum, fatty acids, and peptides in the duodenal lumen.
What type of input does the Enteric Nervous System (ENS) receive?
Extrinsic input from the Autonomic Nervous System (ANS), but can function independently.
Where is Cholecystokinin (CCK) produced?
In I cells located in the duodenum and jejunum.
What condition is being described in the case of the 3-year-old boy?
Toxic megacolon.
What are the two main plexuses of the Enteric Nervous System?
Myenteric plexus and Submucosal plexus.
What is the role of the Submucosal plexus?
It regulates enzyme secretion, blood flow, and absorption.
What occurs during the gastric phase of digestion?
Food is in the stomach.
What are the two main components involved in the regulation of GIT function?
Neural pathways and peptides/other regulatory mediators.
What are the main processes involved in gastrointestinal (GI) functions?
Ingestion, digestion and absorption, elimination, and integrated control.
What is the key role of Secretin?
Control of pancreatic HCO3− secretion.
What is leptin and what role does it play in appetite regulation?
Leptin is a 'satiety hormone' secreted by fat cells that stimulates neurons to decrease appetite and inhibits those that increase appetite.
What is the primary function of digestive reflexes?
To coordinate the processes of digestion and absorption.
Where is Secretin produced?
In S cells of the duodenum.
How is digestion and absorption of food coordinated?
With secretions from glands and motility of the gastrointestinal tract (GIT).
What does digestion refer to?
The breakdown of food into smaller components that can be absorbed into the bloodstream.
What is ingestion in the context of GIT functions?
The taking of food, drugs, liquids, or other substances into the body by mouth.
Which hormones inhibit appetite besides leptin?
Insulin and GLP-1 also inhibit appetite.
What is the key role of Cholecystokinin (CCK)?
Control of gastric emptying and pancreatic enzyme release.
What is extrinsic neural control?
It refers to the regulation of gastrointestinal functions by external neural inputs, primarily from the autonomic nervous system.
Where are long reflexes integrated in the GIT?
In the Central Nervous System (CNS).
How much secretion occurs daily in the gastrointestinal tract?
7 to 10 liters.
What is ghrelin and how does it affect appetite?
Ghrelin is a 'hunger hormone' secreted by gastric cells that increases appetite.
What inhibits the release of Secretin?
Neutral pH in the duodenum and somatostatin.
What stimulates the gastric phase of digestion?
Stomach distension and the presence of peptides and amino acids in the stomach.
What is intrinsic neural control?
It refers to the regulation of gastrointestinal functions by the enteric nervous system, independent of external influences.
What connects the CNS and ENS in the regulation of GIT function?
The Autonomic Nervous System (ANS).
Which part of the nervous system is primarily involved in extrinsic neural control?
The autonomic nervous system.
What role does motility play in the gastrointestinal tract?
It is essential for the movement of food and coordination of digestion and absorption.
What role do sensory receptors play in digestive reflexes?
They detect changes in the gastrointestinal environment and initiate reflex responses.
How do leptin, insulin, GLP-1, and ghrelin interact with the hypothalamus?
They act on feeding centers in the hypothalamus, which integrates these signals into an overall hunger/satiety feeling.
What does GIP stand for?
Gastric Inhibitory Polypeptide.
What is the key role of gastrin?
Stomach acid regulation.
What type of reflexes does the ENS use?
Local reflexes.
What role does the enteric nervous system play in intrinsic neural control?
It coordinates local reflexes and regulates digestive processes within the gastrointestinal tract.
What are the effects of Secretin?
Stimulates pancreatic HCO3− and H2O secretion, neutralizing small intestine acidity from stomach acid, and inhibits H+ secretion by gastric parietal cells.
What are the two main components of the autonomic nervous system involved in extrinsic control?
The sympathetic and parasympathetic nervous systems.
What are paracrine regulatory mediators?
Substances released from endocrine cells in the GI mucosa that diffuse short distances to target cells in the GIT.
What is secretion in the context of GIT functions?
Production and release of a substance by a gland or cell.
What stimuli trigger the release of Cholecystokinin (CCK)?
Small peptides, amino acids, fatty acids, and monoglycerides.
What other factor, besides hormones, influences appetite regulation?
Blood glucose levels also influence appetite regulation.
What is the effect of the parasympathetic nervous system on the digestive system?
Excitatory.
What is the function of GLP?
Glucagon-Like Peptide, involved in insulin secretion and appetite regulation.
What is the function of the Myenteric plexus?
Control of enteric motility.
How does intrinsic neural control differ from extrinsic neural control?
Intrinsic control operates independently within the GIT, while extrinsic control involves external inputs from the central nervous system.
What is somatostatin and where is it secreted?
A paracrine mediator secreted throughout the GIT in response to luminal H+.
What are the effectors involved in the gastric phase?
Hormones, paracrines, and neurotransmitters.
What does the Submucosal plexus regulate?
Secretions and blood flow.
How does the sympathetic nervous system affect gastrointestinal activity?
It generally inhibits gastrointestinal activity and reduces digestive functions.
Where is gastrin produced?
In G cells of the gastric antrum after a meal.
What does excretion mean in relation to the GIT?
The process of eliminating or expelling waste matter.
What inhibits the release of Cholecystokinin (CCK)?
Absence of stimuli (via absorption) and somatostatin.
What inhibits the secretion of somatostatin?
Vagal stimulation.
What role does the parasympathetic nervous system play in gastrointestinal function?
It stimulates gastrointestinal activity and promotes digestion.
What are the components of the enteric nervous system involved in intrinsic control?
The myenteric and submucosal plexuses.
What does VIP stand for?
Vasoactive Intestinal Peptide.
What actions occur during the gastric phase?
Increased secretions and motility.
How often does the boy open his bowels?
Only weekly.
What stimulates the release of gastrin?
Small peptides and amino acids in the stomach, stomach distension, and vagal stimulation via gastrin-releasing peptide (GrP).
What are the effects of Cholecystokinin (CCK)?
Stimulates pancreatic enzyme and HCO3− secretion, slows gastric emptying, induces gallbladder contraction, and stimulates hepatic bile production.
What effects does somatostatin have on GI hormones?
It inhibits the release of all GI hormones and gastric H+ secretion.
From where does the Submucosal plexus receive sensory information?
From chemo- and mechanoreceptors.
What is the role of Gastrin-Releasing Peptide (GRP)?
Stimulates the release of gastrin from G cells.
What is a key feature of intrinsic neural control?
It allows for local reflexes to occur without the need for input from the brain or spinal cord.
What types of receptors are involved in receiving stimuli related to digestion?
Chemoreceptors and mechanoreceptors.
What are the results of the gastric phase?
Digestion of proteins by pepsin, formation of chyme, and controlled entry of chyme into the small intestine.
What significant growth change has the boy experienced?
His growth has fallen from the 25th to the 2nd centile for height and weight.
What happens during gallbladder contraction induced by CCK?
Bile secretion occurs, which can cause pain if gallstones are present.
What inhibits the release of gastrin?
High stomach H+ (acidity) and somatostatin.
What is the primary function of epithelial cells in the gastrointestinal tract?
Specialized for various secretions and absorption of nutrients.
What types of signaling modes are involved in gastric parietal cell signal integration?
Neural (vagus nerve), hormone (gastrin), and paracrine (histamine, SST, prostaglandins).
What triggers the increase in salivary secretion during the cephalic phase?
Food thoughts, smells, and sight.
What are the two main components of the Enteric Nervous System?
Myenteric plexus (Auerbach) and Submucosal plexus (Meissner).
What are the two main plexuses of the Enteric Nervous System?
Myenteric Plexus and Submucosal Plexus.
What role does histamine play in the gastric mucosa?
It is secreted by mast cells and increases gastric H+ secretion directly and by potentiating gastrin and vagal stimulation.
What is Substance P associated with?
Pain transmission and inflammation in the gastrointestinal tract.
What stimuli do chemoreceptors and mechanoreceptors respond to?
Stretch/distension and composition of fluid.
What did the examination reveal about the boy's abdomen?
A distended abdomen with palpable stool throughout.
What are the effects of gastrin?
Increases H+ secretion by gastric parietal cells and stimulates growth of gastric mucosa.
What role does the muscularis mucosa play in the GIT?
Contractions change the surface areas for secretion or absorption.
What is the role of the vagus nerve in gastric parietal cell signaling?
It provides neural signaling.
What are the effects of the cephalic phase on gastric, pancreatic, and intestinal secretions?
It increases their secretions.
What are GIT Regulators?
Hormones and peptides that regulate gastrointestinal functions.
What do endocrine cells in the digestive system produce?
Regulatory peptides.
What is absent in the aganglionic portion of the large bowel?
Submucosal and myenteric plexi.
What are the main components of the gastrointestinal (GI) tract?
Esophagus, Stomach, Small Intestine, Large Intestine, Anus.
What is the function of circular muscle in the GIT?
Contractions decrease the diameter of the lumen.
Which hormone is involved in gastric parietal cell signaling?
Gastrin.
What types of receptors are found in the GIT?
Chemoreceptors, osmoreceptors, and mechanoreceptors.
What are some paracrine signals involved in gastric parietal cell function?
Histamine, somatostatin (SST), and prostaglandins.
What triggers the entry of chyme into the small intestine (SI)?
The entry of chyme itself.
What is the role of long reflexes in the cephalic phase?
They mediate the physiological responses.
What is the role of neural control in the digestive system?
Regulation of motility and secretions.
What is the condition of the proximal colon in this case?
Massive distension.
What are the accessory organs of the GI tract?
Salivary glands, Liver, Gall bladder, Pancreas.
What does longitudinal muscle do in the gastrointestinal tract?
Contraction shortens the segment of the GIT.
What are the two types of fibers in the Enteric Nervous System?
Afferent fibers and efferent fibers.
What are the afferent signals involved in the cephalic phase?
Sight, smell, and food in the mouth.
What type of innervation does the parasympathetic system provide to the GIT?
Excitatory.
What is the function of the esophagus in the GI tract?
To transport food from the mouth to the stomach.
What are the two main plexuses involved in the integration of GIT functions?
Submucosal plexus (Meissner) and Myenteric plexus.
What functions do the submucosal and myenteric plexuses integrate?
Motility, secretory, and endocrine functions of the GIT.
Which part of the brain acts as the coordinating center during the cephalic phase?
Medulla oblongata.
What are the effectors involved in the cephalic phase?
Vagus nerve and enteric nervous system (ENS).
What are the two types of reflexes in the Enteric Nervous System?
Short reflexes and long reflexes.
What is the significance of signal integration in gastric parietal cells?
It involves integration and overlap of different signaling modes for end organ responses.
Which nerves are involved in the parasympathetic innervation of the upper GIT?
Vagus nerve.
What is the primary action that occurs when chyme enters the SI?
A series of reflexes that aid digestion and motility.
What is Vasoactive Intestinal Peptide (VIP) homologous to?
Secretin.
What is the role of the small intestine in digestion?
To absorb nutrients from digested food.
What is the primary function of the stomach?
To digest food and mix it with gastric juices.
What is the cephalic phase?
The initial phase of digestion triggered by the thought, sight, or smell of food.
What role do sympathetic and parasympathetic systems play in the GIT?
They provide extrinsic neural control.
Which neurotransmitter is associated with smooth muscle contraction in the gut?
Substance P.
What effect does Vasoactive Intestinal Peptide (VIP) have on gastric H+ secretion?
It inhibits gastric H+ secretion.
Where do preganglionic sympathetic fibers synapse?
In the prevertebral ganglia.
What is the role of preganglionic fibers in the parasympathetic innervation of the GIT?
They synapse on plexi.
What does Vasoactive Intestinal Peptide (VIP) stimulate in the pancreas?
HCO3- secretion.
What is the significance of blood vessels in the GIT?
They supply nutrients and oxygen to the gastrointestinal tissues.
What is the function of the liver in the GI tract?
To produce bile, which helps in the digestion of fats.
What are the two main incretins discussed?
GIP (Gastric Inhibitory Peptide) and GLP-1 (Glucagon-like Peptide-1).
What stimulates the release of GIP?
Luminal glucose and fatty acids.
What is one of the effects of incretins related to appetite?
Induction of satiety.
What are neurocrines?
Peptides released by the nerves within the gut that have short-range effects.
What is the primary function of Vasoactive Intestinal Peptide (VIP)?
To limit acidification and relax GI smooth muscle.
What is the main function of the large intestine?
To absorb water and form waste products.
What is the origin of sympathetic fibers for the GIT?
Thoracolumbar fibers (T5 - L2).
What are paracrines?
Substances that act locally within the same tissue and have short-range effects.
What is the action range of neurocrines and paracrines?
Short-range effects.
What primarily stimulates GLP-1 release?
Fatty acids and bile in the ileum.
What is the function of secretory cells in the GIT?
To secrete digestive enzymes and other substances.
What type of innervation does the sympathetic system provide to the GIT?
Inhibitory.
Name two hormones involved in endocrine regulation.
Gastrin and secretin.
What do the plexi in the GIT relay information to?
Target cells.
What is the key role of incretins?
Regulation of glucose metabolism, satiety, and pacing.
How does GLP-1 affect glucagon secretion?
It decreases glucagon secretion.
Where do postganglionic fibers of the parasympathetic system synapse?
On smooth muscle, secretory, and endocrine cells.
What is the purpose of the anus in the GI tract?
To expel waste from the body.
What stimulates gastrin release from G cells?
Gastrin-releasing peptide (GRP), also known as bombesin.
How do Enkephalins affect intestinal fluid and electrolyte secretion?
They inhibit it.
Where is GIP produced?
In K cells located in the duodenum and proximal jejunum.
What is one effect of GLP-1 on gastric emptying?
It slows gastric emptying.
What phase of digestion is associated with the entry of chyme into the SI?
Intestinal Phase.
What defines endocrine/hormonal regulation in the gastrointestinal tract?
Hormones synthesized by cells in the gastric and intestinal epithelium and released into the bloodstream for systemic long-range action.
What type of fibers are postganglionic sympathetic fibers?
Adrenergic.
What is the role of the pancreas in digestion?
To produce digestive enzymes and bicarbonate.
Where is GLP-1 produced?
In L cells located in the proximal jejunum and colon.
How does the CNS influence contraction and relaxation in the GIT?
Through neural signals and hormonal regulation.
What role do salivary glands play in digestion?
They produce saliva, which begins the digestion of carbohydrates.
What does the gall bladder do?
Stores and concentrates bile from the liver.
What therapeutic use do Enkephalins have?
They are used in diarrhea treatment.
What effect does GIP have on insulin secretion?
Increased insulin secretion.
What is the role of norepinephrine in the gut?
It is involved in relaxation of smooth muscle.
What is the role of Nitric Oxide (NO) in the gastrointestinal tract?
Smooth muscle relaxation.
What is the effect of Enkephalins on GI smooth muscle?
Contraction, particularly of sphincters.
What are the two main plexi in the enteric nervous system?
Myenteric plexus (Auerbach) and Submucosal plexus (Meissner).
What are some agonist drugs for incretins?
Ozempic (for type 2 DM) and Wegovy (for weight loss).
Which substances are examples of paracrines?
Histamine and somatostatin.
What is the action range of endocrine hormones?
Systemic long-range action.
What effect does GIP have on gastric H+ secretion?
Decreased gastric H+ secretion.
