Why does histamine release during an asthma attack cause airway constriction, rather than dilation, despite some histamine receptors promoting vasodilation elsewhere in the body?

💡 Explanation

During an asthma attack, the predominant histamine receptors in bronchial smooth muscle are H1 receptors. Activation of these receptors causes bronchoconstriction because they trigger intracellular calcium release and smooth muscle contraction; therefore, airway constriction occurs, rather than dilation mediated by H2 receptors in other tissues.

• Why does thickened mucus in the alveoli of cystic fibrosis patients impair gas exchange more than reduced lung elasticity?
• Why does long-term hyperglycemia increase the risk of neurodegenerative diseases involving tau protein aggregates?
• If an elderly patient experiences a hip fracture following a fall, which mechanism most directly contributes to the prolonged recovery specifically due to sarcopenia?
• What causes reduced erythropoietin production when kidney filtration declines?
• What distinguishes presbycusis-related hearing loss from noise-induced hearing loss in a sound engineer who regularly monitors high-decibel audio?
• If a patient's pancreas fails to produce sufficient bicarbonate during digestion, which consequence follows regarding fat absorption?