What effect does a sympathetic antagonist have on bronchi?

A sympathetic antagonist, also known as a sympatholytic agent, works by blocking the effects of the sympathetic nervous system, which is responsible for the "fight or flight" response. One of the key functions of the sympathetic nervous system is the promotion of bronchodilation through the activation of beta-2 adrenergic receptors in the airways. These receptors, when stimulated, cause the smooth muscle in the bronchi to relax, leading to widening of the air passages and easier breathing.

When a sympathetic antagonist is introduced, it inhibits the action of the sympathetic nervous system. This leads to a decrease in bronchodilation and may result in bronchoconstriction, as the normal relaxing signals are blocked. Consequently, this can cause the bronchi to constrict rather than dilate, making it more difficult for air to flow through the respiratory system.

Thus, the correct answer reflects the physiological response that occurs when the sympathetic nervous system's actions are inhibited, resulting in bronchoconstriction.