the upper motor neurons that control skeletal muscles are found in motor cortex.
the upper motor neurons that control skeletal muscles are found in motor cortex.
where are the upper motor neurons that control skeletal muscles found?
motor cortex
the basic route of nerve signals within the efferent somatic nervous system involves a sequence that begins in the upper cell bodies of motor neurons (upper motor neurons) within the 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 axons to control skeletal (voluntary) muscles. these stimuli are conveyed from upper motor neurons through the ventral horn of the spinal cord, and across synapses to be received by the sensory receptors of alpha motor neurons (large lower motor neurons) of the brainstem and spinal cord.
somatic nervous system
distinct skeletal muscles are controlled by groups of individual motor units. such motor units are made up of a single motor neuron and the muscle fibers that it innervates. motor neurons are located in the ventral horn of the spinal cord and the brainstem. these neurons innervate skeletal muscle fibers through the propagation of action potentials down their axons (through ventral roots and cranial nerves), and they stimulate skeletal muscle fibers at neuromuscular junctions where they synapse with the motor end plates of muscle fibers. in humans, these axons can be as long as one meter. motor neurons themselves fall into three main classes: alpha-motor neurons control extrafusal muscle fibers, meaning that they innervate skeletal muscles leading to movement; gamma-motor neurons innervate intrafusal muscle fibers, controlling the sensitivity of muscle spindles to stretch; beta-motor neurons are capable of synapsing on either type of muscle fiber. alpha-motor neurons can further be divided into three separate subclasses, distinguished according to the contractile properties of the motor units that they form: fast-twitch fatigable (ff), fast-twitch fatigue-resistant (fr), and slow-twitch fatigue-resistant (s). the composition of a motor pool may consist of multiple classes and subclasses of motor neurons.
motor pool (neuroscience)