Anticholinergics (anticholinergic agents) are substances that block the action of the neurotransmitter called acetylcholine (ACh) at synapses in the central and peripheral nervous system.These agents inhibit the parasympathetic nervous system by selectively blocking the binding of ACh to its receptor in nerve cells. The nerve fibers of the parasympathetic system are responsible for the involuntary movement of smooth muscles present in the gastrointestinal tract, urinary tract, lungs, sweat glands, and many other parts of the body.In broad terms, anticholinergics are divided into two categories in accordance with their specific targets in the central and peripheral nervous system and at the neuromuscular junction: antimuscarinic agents, and antinicotinic agents (ganglionic blockers, neuromuscular blockers).The term "anticholinergic" is typically used to refer to antimuscarinics which competitively inhibit the binding of ACh to muscarinic acetylcholine receptors; such agents do not antagonize the binding at nicotinic acetylcholine receptors at the neuromuscular junction, although the term is sometimes used to refer to agents which do so.
In normal muscle cells, the various parts of the muscle fibers that make up the sarcomere are distributed evenly in a pattern for effective muscle contraction. Evidence suggests that some kinds of NM affect the arrangement of these muscle fibers, causing the muscles to be unable to contract as efficiently or effectively. Nemaline myopathy is usually genetic and shows traits in the affected individual from birth or an early age. However, there are some cases of symptoms of nemaline myopathy not showing up until adulthood. These cases are usually not genetic. Of the genes that have been linked to nemaline myopathy, most are also involved in encoding proteins in the sarcomeres in the muscle cells. Respiratory muscles are often more affected than other skeletal muscle groups. Cardiac muscle is usually not affected in nemaline myopathy; however, in cases where it does, patients often present with dilated cardiomyopathy. The ocular muscles are usually spared.The different genes whose mutations lead to the different kinds of nemaline myopathies affect the cells and the persons body differently. The first kind of nemaline myopathy identified is due to the Slow α-Tropomyosin Gene TPM3 and varies from case to case with its severity. In this kind of nemaline myopathy, affected people are weaker and more affected in their lower limbs than their upper limbs.As stated above, the most common genetic form of NM is caused by a mutation in the nebulin gene, called Nebulin, and has a range of severity levels.