A muscle spindle, with γ motor and Ia sensory fibers
Identifiers
MeSH
D009047
NeuroLex ID
sao1438006234
FMA
83660
Anatomical terms of neuroanatomy
[edit on Wikidata]
A gamma motor neuron (γ motor neuron), also called gamma motoneuron, or fusimotor neuron, is a type of lower motor neuron that takes part in the process of muscle contraction, and represents about 30% of (Aγ) fibers going to the muscle.[1][2] Like alpha motor neurons, their cell bodies are located in the anterior grey column of the spinal cord. They receive input from the reticular formation of the pons in the brainstem. Their axons are smaller than those of the alpha motor neurons, with a diameter of only 5 μm. Unlike the alpha motor neurons, gamma motor neurons do not directly adjust the lengthening or shortening of muscles. However, their role is important in keeping muscle spindles taut, thereby allowing the continued firing of alpha neurons, leading to muscle contraction. These neurons also play a role in adjusting the sensitivity of muscle spindles.[3]
The presence of myelination in gamma motor neurons allows a conduction velocity of 4 to 24 meters per second, significantly faster than with non-myelinated axons[4][5] but slower than in alpha motor neurons.
^Macefield, VG; Knellwolf, TP (1 August 2018). "Functional properties of human muscle spindles". Journal of Neurophysiology. 120 (2): 452–467. doi:10.1152/jn.00071.2018. PMID 29668385.
^Hunt, C. (1951) "The reflex activity of mammalian small-nerve fibres." Journal of Physiology. 115(4): 456–469.
^Burke, D., Skuse, N.F., Stuart, D.G. (1979) "The regularity of muscle spindle discharge in man." Journal of Physiology. 291: 277–290
^Andrew BL, Part NJ (1972) Properties of fast and slow motor units in hind limb and tail muscles of the rat. Q J Exp Physiol Cogn Med Sci 57:213-225.
^Russell NJ (1980) Axonal conduction velocity changes following muscle tenotomy or deafferentation during development in the rat. J Physiol 298:347-360.
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