Emergency Central is a collection of disease, drug, and test information including 5-Minute Emergency Medicine Consult, Davis’s Drug, McGraw-Hill Medical’s Diagnosaurus®, Pocket Guide to Diagnostic Tests, and MEDLINE Journals created for emergency medicine professionals. Explore these free sample topics:
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- Cardiovascular: β1-receptors:
- ATP converted to cAMP by adenyl cyclase with stimulation of β-receptors.
- cAMP activates protein kinase, which phosphorylates proteins of the sarcoplasmic reticulum.
- Sarcoplasmic reticulum releases calcium.
- Excitation–contraction coupling occurs.
- Effects of β-blockers:
- Decreased excitation/contraction
- Membrane stabilizing activity
- Sodium channel blockade causes a prolongation of the QRS complex (with some agents).
- Prolongation of QTc interval leading to ventricular dysrhythmias (with some agents)
- Intrinsic sympathomimetic activity
- Partial agonist properties (with some agents)
- CNS effects with the lipophilic agents (propranolol, metoprolol, labetalol)