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Another important site of histamine storage and release is the enterochromaffin-like (ECL) cell of the stomach. The most important pathophysiologic mechanism of mast cell and basophil histamine release is immunologic. These cells, if sensitized by IgE antibodies attached to their membranes, degranulate when exposed to the appropriate antigen.
1) In the body of the stomach, the vagal postganglionic muscarinic nerves release acetylcholine (ACh) which stimulates parietal cell H+ secretion. 2) In the lamina propria of the body of the stomach the ACh released from the vagal endings triggers histamine secretion from ECL cells. Histamine also stimulates H+ secretion from parietal cells.
The cephalic phase: Thirty percent of the total gastric acid secretions to be produced is stimulated by anticipation of eating and the smell or taste of food. This signalling occurs from higher centres in the brain through the vagus nerve (Cranial Nerve X). It activates parietal cells to release acid and ECL cells to release histamine.
Histamine is an organic compound that primarily functions in service of the human body's immune responses as well as for the regulation of many physiological functions. [1] Since their discovery in 1910, [ 2 ] histamines have been known to trigger inflammatory responses such as itching as part of an immune response to foreign pathogens; for ...
This triggers G cells to release gastrin, which in turn stimulates parietal cells to secrete gastric acid. Gastric acid is about 0.5% hydrochloric acid, which lowers the pH to the desired pH of 1–3. Acid release is also triggered by acetylcholine and histamine. The intestinal phase has two parts, the excitatory and the inhibitory.
In mammals, histamine is an important biogenic amine with regulatory roles in neurotransmission, gastric acid secretion and immune response. [1] [2] Histidine decarboxylase is the sole member of the histamine synthesis pathway, producing histamine in a one-step reaction. Histamine cannot be generated by any other known enzyme.
[1] [2] Histamine is a neurotransmitter involved in various physiological processes. There are four main types of histamine receptors: H1, H2, H3, and H4. H1 receptors are linked to allergic responses, H2 to gastric acid regulation, H3 to neurotransmitter release modulation, and H4 to immune system function. There are four known histamine ...
Histamine, the structure shown, causes a person to feel itchy during an allergic reaction. Conditions caused by food allergies are classified into three groups according to the mechanism of the allergic response: [57] IgE-mediated (classic) – the most common type, occurs shortly after eating and may involve anaphylaxis.