<Li> For vertebrates, however, the response of a muscle fiber to a neurotransmitter can only be excitatory, in other words, contractile . Muscle relaxation and inhibition of muscle contraction in vertebrates is obtained only by inhibition of the motor neuron itself . Muscle innervation may eventually play a role in the maturation of motor activity . This is how muscle relaxants work by acting on the motor neurons that innervate muscles (by decreasing their electrophysiological activity) or on cholinergic neuromuscular junctions, rather than on the muscles themselves . </Li> <P> These are also known as branchial motor neurons, which are involved in facial expression, mastication, phonation, and swallowing . Associated cranial nerves are the oculomotor, abducens, trochlear, and hypoglossal nerves . </P> <Table> <Tr> <Th> Branch of NS </Th> <Th> Position </Th> <Th> Neurotransmitter </Th> </Tr> <Tr> <Td> Somatic </Td> <Td> n / a </Td> <Td> Acetylcholine </Td> </Tr> <Tr> <Td> Parasympathetic </Td> <Td> Preganglionic </Td> <Td> Acetylcholine </Td> </Tr> <Tr> <Td> Parasympathetic </Td> <Td> Ganglionic </Td> <Td> Acetylcholine </Td> </Tr> <Tr> <Td> Sympathetic </Td> <Td> Preganglionic </Td> <Td> Acetylcholine </Td> </Tr> <Tr> <Td> Sympathetic </Td> <Td> Ganglionic </Td> <Td> Norepinephrine * </Td> </Tr> <Tr> <Td_colspan="3"> * Except fibers to sweat glands and certain blood vessels Motor neuron neurotransmitters </Td> </Tr> </Table> <Tr> <Th> Branch of NS </Th> <Th> Position </Th> <Th> Neurotransmitter </Th> </Tr>

Where are the cell bodies of peripheral motor neurons located