How is gastric acid secretion regulated?
Gastric acid secretion is regulated by three local hormones: acetylcholine, gastrin, and histamine. Of these three, acetylcholine has the largest effect. Parietal cells, G cells, and enterochromaffin-like cells are stimulated by acetylcholine released in response to vagus nerve simulation.
What is regulation of gastric secretion?
Gastric secretion is finely regulated by neural, hormonal, and paracrine pathways. During ingestion of a meal, the pathways can be activated by stimuli originating in the brain or stimuli originating in the stomach, such as mechanical stimulation (eg, distension) or chemical stimulation (eg, protein).
Why is acid released in the stomach?
Acid is secreted by parietal cells in the proximal two thirds (body) of the stomach. Gastric acid aids digestion by creating the optimal pH for pepsin and gastric lipase and by stimulating pancreatic bicarbonate secretion.
Which would trigger a cephalic phase response?
The cephalic phase of gastric secretion is initiated by the sight, smell, thought or taste of food. Neurological signals originate from the cerebral cortex and in the appetite centers of the amygdala and hypothalamus. This enhanced secretory activity is a conditioned reflex.
How is gastric function regulated?
The nervous system, and endocrine system collaborate in the digestive system to control gastric secretions, and motility associated with the movement of food throughout the gastrointestinal tract, including peristalsis, and segmentation contractions.
How is gastric motility regulated?
GI motility is controlled by contractility of smooth muscles of the GI tract, extrinsic and intrinsic neurons (motor and sensory) and some hormones. In mammals, ghrelin (GHRL) and motilin (MLN) stimulate appetite and GI motility and contribute to the regulation of energy homeostasis.
What regulates gastric emptying?
Several upper gastrointestinal hormones alter gastric emptying; the most important are CCK, GIP, glucagon, GLP-1 and PYY which retard gastric emptying. These hormones also reduce appetite or induce satiation.
When is gastric acid secreted?
Acid secretion is stimulated by distension of the stomach and by amino acids present in the food. The intestinal phase: The remaining 10% of acid is secreted when chyme enters the small intestine, and is stimulated by small intestine distension and by amino acids.
How is HCl regulated in the stomach?
The three stimulants of gastric acid secretion likely to have physiological roles in regulation of secretion are acetylcholine, gastrin, and histamine. Acetylcholine is released by vagal and intramucosal reflex stimulation, acting directly on the parietal cell.
How is cephalic regulated?
The Cephalic Phase Is Mediated by the Vagus Nerve Through Acetylcholine and Gastrin. The cephalic phase of gastric secretion is mediated entirely through the vagus nerve. A variety of sensory stimuli including the sight, smell, and taste of food elicits acid secretion in the stomach.
What are the three phases of the regulation of gastric activity?
The process of gastric secretion can be divided into three phases (cephalic, gastric, and intestinal) that depend upon the primary mechanisms that cause the gastric mucosa to secrete gastric juice.