The cell bodies of motor neurons that innervate skeletal muscles are located in the ventral horn of the grey matter of the spinal cord. Axons of these nerves leave via the ventral root and travel to the appropriate skeletal muscle.
A single motor neuron can form synapses with many muscle fibers, due to a multiplicity of axon collaterals. An individual motor neuron and all the muscle fibers it innervates is called a motor unit, the functional unit of the neuromuscular system.
Motor units can vary in size. The smallest consist of a single motor neuron that innervates just a few muscle cells. Such an arrangement is typical in situations where very precise control of fine movements is necessary (e.g. finger or eye movements). A large motor unit may innervate hundreds of muscle cells. Such units are responsible for gross movements such as leg or trunk movements. The smaller the motor unit, the greater precision of fine motor skills.
A single motor neuron can form synapses with many muscle fibers, due to a multiplicity of axon collaterals. An individual motor neuron and all the muscle fibers it innervates is called a motor unit, the functional unit of the neuromuscular system.
Motor units can vary in size. The smallest consist of a single motor neuron that innervates just a few muscle cells. Such an arrangement is typical in situations where very precise control of fine movements is necessary (e.g. finger or eye movements). A large motor unit may innervate hundreds of muscle cells. Such units are responsible for gross movements such as leg or trunk movements. The smaller the motor unit, the greater precision of fine motor skills.
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