Term
| Where is histamine present in the body? |
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Definition
| It is present in practically all tissue, though it is highest in skin, lungs and GI tract and lowest in plasma. |
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Term
| Which cells synthesize and store histamine? |
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Definition
| Mast cells in the skin and basophils in the blood |
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Term
| Which immunoglobulin class is responsible for producing the antibodies which initiate allergic reaction? |
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Definition
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Term
| Can allergic release of histamine occur on initial allergen exposure? |
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Definition
| No. Prior exposure to the allergen is necessary for the release of histamine. |
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Term
| What are the two receptors for histamine? |
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Definition
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Term
| What are the effects of H1 stimulation? |
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Definition
1. Vasodilation - causes warmth and redness of the skin
2. Increased Capillary Permeability - more fluid in the interstitial spaces cause swelling and can cause decrease BP
3. Bronchoconstriction - breathing difficulties such as asthma
4. CNS effects - role in cognition, sleep/wake cycle, and memory. May suppress seizures
5. Activation on sensory nerves produces itching, pain and secretion of mucus |
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Term
| What is the major response to H2 receptor activation? |
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Definition
| secretion of gastric acid |
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Term
| What compounds besides histamine play a role in allergic reaction? |
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Definition
| Prostaglandins, leukotrienes, tryptase |
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Term
| What are the principle mediators in anaphlaxis? |
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Definition
| substances such as leukotrienes |
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Term
| Which drug is preferred for the treatment of anaphylaxis? |
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Definition
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Term
| What are the two types of antihistamine? |
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Definition
1. H1 antagonists - used for mild allergic reactions
2. H2 antagonists - used for treatment of gastric and duodenal ulcers |
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Term
| What is the difference between first generation and second generation H1 antagonists? |
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Definition
| First generation H1 antagonists are highly sedating and second generation H1 antagonists are not. |
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Term
| Blocade of which nonhistamine receptor is responsible for most of the side effects presented by H1 receptor antagonists? |
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Definition
| Muscarinic cholinergic receptors |
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Term
| Which depresses the CNS, first generation or second generation H1 antagonists? |
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Definition
| 1st generation H1 antagonists cause the most CNS depression |
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Term
| Why are antihistamines effective in treating motion sickness? |
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Definition
| blocade of H1 and muscarinic receptors leading from the vestibular apparatus of the inner ear to the vomiting center of the medulla. |
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Term
| what is the most common side effect of antihistamines? |
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Definition
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