Figure 1: Autonomous control of airway smooth muscle. A. General scheme of the cholinergic and adrenergic innervation controlling airway smooth muscle cell (ASMC) contraction. Black dots represent the nervous ganglia. ACh: acetylcholine. NAdr: noradrenalin. Adr: adrenalin. Cholinergic innervation directly stimulates ASMC contraction. Adrenergic stimulation indirectly modulates ASMC contraction acting of parasympathetic ganglia, with small direct action on ASMC. ASMC may be also sensitive to adrenalin B. Schema of the parasympathetic pathway controlling ASMC contraction. prg. fiber: preganglionic fiber. postg: postganglionic fiber. N: nicotinic receptor. M1, M2, M3: muscarinic receptors type 1, 2, 3. Nervous stimulus is transmitted in the ganglia from preganglionic to postgangionic fibers via activation of nicotinic receptors. At the neuromuscular junction, ACh acts on M3 and M1 receptors on ASMC. M1 and M2 receptors are responsible for retroactive control of ACh release in the ganglia, and at the neuromuscular junction, respectively.