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A motor nerve, or efferent nerve, is a nerve that contains exclusively efferent nerve fibers and transmits motor signals from the central nervous system (CNS) to the muscles of the body. This is different from the motor neuron , which includes a cell body and branching of dendrites, while the nerve is made up of a bundle of axons.
A motor neuron (or motoneuron or efferent neuron [1]) is a neuron whose cell body is located in the motor cortex, brainstem or the spinal cord, and whose axon (fiber) projects to the spinal cord or outside of the spinal cord to directly or indirectly control effector organs, mainly muscles and glands. [2]
Type I cells can be further classified by the location of the soma. The basic morphology of type I neurons, represented by spinal motor neurons, consists of a cell body called the soma and a long thin axon covered by a myelin sheath. The dendritic tree wraps around the cell body and receives signals from other neurons.
Groups of motor units often work together as a motor pool to coordinate the contractions of a single muscle. The concept was proposed by Charles Scott Sherrington. [2] Usually muscle fibers in a motor unit are of the same fiber type. [3] When a motor unit is activated, all of its fibers contract.
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 into the periphery to innervate skeletal muscles. An alpha motor neuron and the muscle fibers it innervates comprise a motor ...
Structure of a typical neuron with Schwann cells in the peripheral nervous system. The nervous system is defined by the presence of a special type of cell—the neuron (sometimes called "neurone" or "nerve cell"). [5]
The entire nerve is wrapped in a layer of connective tissue called the epineurium. Nerve cells (often called neurons) are further classified as sensory, motor, or mixed nerves. In the central nervous system, the analogous structures are known as nerve tracts. [1] [2]
When the motor nerve is stimulated there is a delay of only 0.5 to 0.8 msec between the arrival of the nerve impulse in the motor nerve terminals and the first response of the endplate [7] The arrival of the motor nerve action potential at the presynaptic neuron terminal opens voltage-dependent calcium channels, and Ca 2+ ions flow from the ...