Question

propranolol, a beta - blocker, is typically used to __________. multiple choice increase heart rate decrease heart rate produce vasoconstriction of the coronary arteries produce vasodilation of blood vessels of skeletal muscle produce bronchodilation

Explanation:

Beta - blockers like propranolol work by blocking beta - adrenergic receptors. This action affects the heart. Beta - 1 receptors are present in the heart. When blocked, the sympathetic nervous system's influence on the heart is reduced. The sympathetic nervous system typically increases heart rate (through effects on beta - 1 receptors). By blocking these receptors, propranolol decreases the heart rate.
For vasoconstriction of coronary arteries: Beta - blockers do not have a direct action to cause vasoconstriction of coronary arteries. In fact, in some cases, the reduced heart rate (due to beta - blockade) can indirectly improve coronary blood flow.
For vasodilation of skeletal muscle blood vessels: Beta - 2 receptors (which are less affected by non - selective beta - blockers like propranolol compared to beta - 1 receptors) are involved in vasodilation of some blood vessels. But propranolol's main action is not on skeletal muscle blood vessel vasodilation.
For bronchodilation: Beta - 2 receptors are also in the bronchi. Blocking beta - 2 receptors (by non - selective beta - blockers like propranolol) can potentially cause bronchoconstriction, not bronchodilation.

Answer:

decrease heart rate