08.01 The Somatic Nervous System
Figure 8.1 Neuromuscular junction (Copyright QUT, Sheila Doggrell)
Acetylcholine receptors were initially divided on their basis of responses to nicotine and muscarine, into those that responded to nicotine, nicotinic receptors, and those that responded to muscarine, muscarinic receptors. The NN receptors are found at the autonomic ganglia, adrenal medulla and within the central nervous system. The NM receptors are found on skeletal muscle innervated by the somatic nervous system. The NM receptor can be stimulated by increasing the concentration of acetylcholine in the synapse and inhibited by neuromuscular blockers.
The somatic/voluntary nervous system is distinguishable from the branches of the autonomic nervous system by having no ganglia. The nerves arising from the spinal cord release acetylcholine onto NM, the nicotinic receptors associated with skeletal muscle (Figure 8.1).
