==Transmisión de sinais nerviosos==
The somatic nervous system controls all [[voluntary muscle|voluntary muscular]] systems within the body, with the exception of [[reflex arc]]s.
The basic route of [[nerve signal]]s within the [[efferent nerve fiber|efferent]] somatic nervous system involves a sequence that begins in the upper [[Cell (biology)|cell bodies]] of [[motor neuron]]s ([[upper motor neuron]]s) within the [[Brodmann area 4|precentral gyrus]] (which approximates the [[primary motor cortex]]). Stimuli from the precentral gyrus are transmitted from upper motor neurons and down the [[corticospinal tract]], via [[axon]]s to control skeletal (voluntary) muscles. These stimuli are conveyed from upper motor neurons through the [[Anterior horn of spinal cord|ventral horn]] of the [[spinal cord]], and across [[synapse]]s to be received by the [[sensory receptor]]s of [[alpha motor neurons]] (large [[lower motor neuron]]s) of the [[brainstem]] and [[spinal cord]].
Upper motor neurons release a [[neurotransmitter]], [[acetylcholine]], from their axon terminal knobs, which are received by [[nicotinic acetylcholine receptor|nicotinic receptors]] of the alpha motor neurons. In turn, alpha motor neurons relay the [[stimulus (physiology)|stimulus]].