12 Questions
What is the primary function of histamine in physiological processes?
To regulate gut, cardiovascular, and lung function through slow release
Which of the following is a systemic effect of histamine release?
Bronchoconstriction and spasm
What is the mechanism of action of H1 receptor antagonists?
Competitive antagonism of histamine at the H1 receptor
Which of the following is a side effect of glucocorticoids?
Diabetes and osteoporosis
What is the primary mechanism of action of glucocorticoids?
Gene expression changes through nuclear receptor binding
What is the function of prostaglandins?
Pro-inflammatory lipid mediators
What is the primary difference between older and newer H1 receptor antagonists?
Older antagonists can pass the blood-brain barrier, while newer ones cannot
Histamine is derived from the amino acid Tryptophan.
False
H2 receptor activation leads to bronchoconstriction.
False
Newer H1 receptor antagonists, such as Loratadine, can pass the blood-brain barrier.
False
Glucocorticoids increase PLA2 activity.
False
Beta adrenoceptor agonists are used to treat anaphylaxis.
True
Study Notes
Histamine
- Derived from Histidine, found in Mast Cells, Basophils, and Neutrophils
- Secretion by slow release is physiologically important for gut, cardiovascular, and lung function
- Mass degranulation activated in response to activated antibody leads to anaphylaxis → mass drop in blood pressure
Histamine Receptors
- H1 receptor activation:
- Bronchoconstriction
- Contraction of gut
- Vasodilation & ↑vascular permeability, dec.bp
- Stimulation of sensory nerves and release of peptide mediators in periphery → vasodilation
- H2 receptor activation:
- Gastric acid secretion
- Heart rate
- H3 receptor:
- Presynaptic nerve terminals
- H4 receptor:
- Mast cells
Histamine Release
- Local:
- Itching
- Redness
- Swelling
- Oedema
- Headache
- Vasodilation
- Bronchoconstriction
- Vomiting
- Diarrhea
- Systemic:
- Huge Vasodilation
- Bronchoconstriction and spasm
Treatment of Histamine Release
- Treated with Beta adrenoceptor agonists
- Antihistamines:
- H1 receptor antagonists
- Older (can pass BBB): Promethazine, chlorpheniramine
- Also anti-muscarinic- sedative effects
- Newer (reduced muscarinic, don't pass BBB): Loratadine, fexofenadine
- Uses: anti-allergy, sedation, cough/cold remedies, antiemetic
- Side effects: Dry mouth, blurred vision, sedation
Steroids
- Glucocorticoids:
- Prednisone
- Beclametasone
- Gene expression changes:
- Decrease PLA2 activity
- Decrease COX expression
- Side effects:
- Diabetes
- Osteoporosis
- Peptic ulcers
- Immunosuppression
- Adrenal suppression
- Altered appearance – gain weight on face and trunk, wasted limbs
- Mental disturbance
- Topical - skin atrophy, hair growth
Explore the role of histamine in physiological processes and its receptors, including H1 receptor activation. Learn about histamine's effects on the gut, cardiovascular, and lung function, as well as its involvement in anaphylaxis. Test your knowledge of histamine and steroids in this lecture bite.
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