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Questions and Answers
What part of the body is primarily affected by the contraction caused by histamine?
What part of the body is primarily affected by the contraction caused by histamine?
What is the first part of the triple response when histamine is injected intradermally?
What is the first part of the triple response when histamine is injected intradermally?
Which type of histamine receptor is mainly associated with allergic conditions?
Which type of histamine receptor is mainly associated with allergic conditions?
What is the effect of histamine on blood vessels?
What is the effect of histamine on blood vessels?
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Which drug is an example of a first-generation H1 receptor blocker?
Which drug is an example of a first-generation H1 receptor blocker?
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What is primarily stimulated by histamine action on H2 receptors?
What is primarily stimulated by histamine action on H2 receptors?
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Which of the following responses results in itching due to histamine release in the skin?
Which of the following responses results in itching due to histamine release in the skin?
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What occurs after a bright red flush (flare) develops due to histamine?
What occurs after a bright red flush (flare) develops due to histamine?
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Study Notes
Triple Response
- The Lewis triple response is a characteristic three-part response that occurs when a pointed object (like a key) is pressed against the skin.
- The response is caused by the release of histamine from mast cells.
Histamine
- Histamine is a chemical messenger that plays a role in various bodily functions.
- It is involved in:
- Allergic and inflammatory reactions
- Gastric acid secretion
- Neurotransmission in parts of the brain
Release of Histamine
- Stimuli that trigger histamine release include cell damage, cold temperatures, bacterial toxins, bee stings, and physical trauma.
- Mast cells release histamine in response to these stimuli.
Action of Histamine
- Histamine causes contraction in smooth muscles of the intestines, airways, and uterus.
- It leads to vasodilation and increased capillary permeability, resulting in swelling (edema).
- Histamine release in the skin causes itching by stimulating sensory nerve endings.
- Histamine stimulates the release of gastric acid.
Allergic Reactions
- Allergens trigger an immune response, resulting in histamine release.
- Symptoms of allergic reactions include:
- Increased mucus secretion
- Blood vessel expansion (causing swelling and edema)
- Contraction of respiratory airways
- Itchiness or rash
Histamine Receptors
- Histamine interacts with different receptors (H1, H2, H3, H4).
- H1 receptors are implicated in allergic responses and sleep disorders.
- H2 receptors are associated with stomach acid secretion.
- H3 and H4 receptors have roles in the central nervous system and inflammatory responses respectively.
Histamine Receptor Blockers
- Medications that target histamine receptors are used to treat various conditions.
- H1 blockers treat allergic reactions and induce sleep.
- First-generation examples: Diphenhydramine
- Second-generation examples: Loratadine
- H2 blockers are used to reduce stomach acid production.
- Example: Ranitidine
Triple Response Symptoms
- A localized red spot appears immediately at the injection site, followed by a bright red flush that spreads beyond the initial area.
- A wheal (swelling) forms in the area within a minute, due to increased fluid permeation through capillaries.
Intradermal Drug Sensitivity Test
- A method to determine if an individual is allergic to a specific drug.
- Involves injecting a small amount of the drug under the skin.
- Reaction is observed for swelling and redness, resembling a hive.
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Description
Explore the Lewis triple response and the role of histamine in the body. This quiz covers how histamine affects allergic reactions, muscle contractions, and skin responses. Test your understanding of the stimuli that trigger histamine release and its physiological effects.
