ANATOMY

Detailed explanation-1: -Dilation and constriction of the airway are achieved through nervous control by the parasympathetic and sympathetic nervous systems. The parasympathetic system causes bronchoconstriction, whereas the sympathetic nervous system stimulates bronchodilation.

Detailed explanation-2: -While the parasympathetic nervous system signals in airway smooth muscle (ASM) cells to cause bronchoconstriction, the sympathetic nervous system increases airway diameter (bronchodilation) by antagonizing the action of the parasympathetic nervous system.

Detailed explanation-3: -The parasympathetic nerves provide the dominant autonomic control of airway smooth muscle. They release acetylcholine onto muscarinic receptors, causing contraction and bronchoconstriction (1). The release of acetylcholine from the parasympathetic nerves is controlled by muscarinic autoreceptors located on the nerves.

Detailed explanation-4: -The sympathetic nervous system is responsible for bronchodilation mediated through its beta-receptors. To evaluate this activity, beta adrenergic blockers such as propanolol are used. When this agent is administered, a descent of conductance is observed.