Beta motor neurons (β motor neurons), also called beta motoneurons, are a kind of lower motor neuron, along with

alpha motor neuron Alpha (α) motor neurons (also called alpha motoneurons), are large, multipolar lower motor neurons of the brainstem and spinal cord. They innervate extrafusal muscle fibers of skeletal muscle and are directly responsible for initiating their con ...

s and gamma motor neurons. Beta motor neurons innervate intrafusal fibers of muscle spindles with collaterals to extrafusal fibers - a type of slow twitch fiber. Also,

axons An axon (from Greek ἄξων ''áxōn'', axis), or nerve fiber (or nerve fibre: see American and British English spelling differences#-re, -er, spelling differences), is a long, slender projection of a nerve cell, or neuron, in vertebrates, th ...

of alpha, beta, and gamma motor neurons become myelinated. Moreover, these efferent neurons originate from the anterior grey column of the spinal cord and travel to skeletal muscles. However, the larger diameter alpha motor fibers require higher conduction velocity than beta and gamma.

Types

There are two kinds of beta motor neuron (as gamma motor neuron) that include: *Static beta motor neurons. These motor neurons innervate nuclear chain fibers of muscle spindles, with collaterals to extrafusal muscle fibers. *Dynamic beta motor neurons. The dynamic type innervates nuclear bag fibers of muscle spindles, with collaterals to extrafusal muscle fibers. Gamma motor neurons innervate only intrafusal fibers of muscle spindles, but extrafusal fibers (i.e. slow and fast fibers) are innervated by alpha motoneurons.

References

*Williams & Warwick. Gray's Anatomy. Thirty-seventh edition. Churchill Livingstone. *https://web.archive.org/web/20100725065352/https://musom.marshall.edu/anatomy/grosshom/Musclesensory.html {{Nervous tissue Somatic motor system Efferent neurons

Types

See also

References