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Acetylcholine binds to nicotinic acetylcholine receptors of alpha-motor neurons. [3] The somatic nervous system controls all voluntary muscular systems within the body, and the process of voluntary reflex arcs. [10] The basic route of nerve signals within the efferent somatic nervous system involves a sequence that begins in the upper cell ...
The target of these neurons varies, but in the somatic nervous system the target will be some sort of muscle fiber. There are three primary categories of lower motor neurons, which can be further divided in sub-categories. [17] According to their targets, motor neurons are classified into three broad categories: [18] Somatic motor neurons
The PNS includes motor neurons, mediating voluntary movement; the autonomic nervous system, comprising the sympathetic nervous system and the parasympathetic nervous system and regulating involuntary functions; and the enteric nervous system, a semi-independent part of the nervous system whose function is to control the gastrointestinal system.
Spatial recruitment is the activation of more motor units to produce a greater force. Larger motor units contract along with small motor units until all muscle fibers in a single muscle are activated, thus producing the maximum muscle force. Temporal motor unit recruitment, or rate coding, deals with the frequency of activation of muscle fiber ...
A simple view, that is almost certainly too limited and that dates back to the earliest work on the motor cortex, is that neurons in the motor cortex control movement by a feed-forward direct pathway. In that view, a neuron in the motor cortex sends an axon or projection to the spinal cord and forms a synapse on a motor neuron. The motor neuron ...
Alpha motor neurons are distinct from gamma motor neurons, which innervate intrafusal muscle fibers of muscle spindles. While their cell bodies are found in the central nervous system (CNS), α motor neurons are also considered part of the somatic nervous system —a branch of the peripheral nervous system (PNS)—because their axons extend ...
The general (spinal) somatic efferent neurons (GSE, somatomotor, or somatic motor fibers) arise from motor neuron cell bodies in the ventral horns of the gray matter within the spinal cord. They exit the spinal cord through the ventral roots , carrying motor impulses to skeletal muscle through a neuromuscular junction .
In addition, in 2015 an all-human neuromuscular junction has been created in vitro using human embryonic stem cells and somatic muscle stem cells. [16] In this model presynaptic motor neurons are activated by optogenetics and in response synaptically connected muscle fibers twitch upon light stimulation.