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Humans have receptors for two kinds of beta adrenergic compounds such as catecholamines to control cardiac muscle contractions. Some are beta 1 receptors that promote increased heart rate. Other drugs, called beta blockers, slow heart rate. Smooth muscle cells, however, have beta 2 receptors, which mediate muscle relaxation. Blockers of these effects are sometimes used to treat asthma.
-The use of beta 2 antagonist drugs may be useful in asthma because they may
A) increase constriction of the skeletal muscle of the chest wall.
B) increase heart rate and therefore allow the patient to get more oxygen circulated.
C) dilate the bronchioles by relaxing their smooth muscle.
D) override the beta blockers that the patient is already taking.
E) obstruct all G protein-mediated receptors.

Question

Quizplus · Accepted Answer

Beta 2 antagonists target the beta 2 receptors found in smooth muscle cells, which would mediate muscle relaxation, including the smooth muscle in the bronchioles. Blocking these receptors would dilate the bronchioles, making it easier for the patient to breathe. The other options are incorrect because beta 2 antagonists have the opposite effect, and they do not override other medications or obstruct G protein-mediated receptors.

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