Beta motor neurons (β motor neurons), also called beta motoneurons, are a few kind of
lower motor neuron, along with
alpha motor neurons 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 spelling differences) is a long, slender projection of a nerve cell, or neuron, in vertebrates, that typically conducts electrical impulses known as action pot ...
of alpha, beta, and gamma motor neurons become
myelinated. Moreover, these efferent neurons originate from the
anterior grey column of the
spinal cord
The spinal cord is a long, thin, tubular structure made up of nervous tissue that extends from the medulla oblongata in the lower brainstem to the lumbar region of the vertebral column (backbone) of vertebrate animals. The center of the spinal c ...
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.
See also
*
Nerve fiber
An axon (from Greek ἄξων ''áxōn'', axis) or nerve fiber (or nerve fibre: see spelling differences) is a long, slender projection of a nerve cell, or neuron, in vertebrates, that typically conducts electrical impulses known as action pot ...
*
Type Ia sensory fiber
*
Type II sensory fiber
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