Lower motor neuron
| Lower motor neuron | |
|---|---|
| Identifiers | |
| FMA | 84632 |
| Anatomical terms of neuroanatomy | |
Lower motor neurons (LMNs) are
fibers and act as a link between upper motor neurons and muscles.[2][3] Cranial nerve lower motor neurons also control some voluntary movements of the eyes, face and tongue, and contribute to chewing, swallowing and vocalization.[4] Damage to the lower motor neurons can lead to flaccid paralysis, absent deep tendon reflexes and muscle atrophy
.
Classification
Lower motor neurons are classified based on the type of muscle fiber they innervate:[5]
- Alpha motor neurons (α-MNs) innervate extrafusal muscle fibers, the most numerous type of muscle fiber and the one involved in muscle contraction.
- Beta motor neurons (β-MNs) innervate intrafusal fibers of muscle spindles with collaterals to extrafusal fibers (type of slow twitch fibers).
- Gamma motor neurons (γ-MNs) innervate intrafusal muscle fibers, which together with sensory afferents compose muscle spindles.[clarification needed] These are part of the system for sensing body position (proprioception).
Physiology
synaptic cleft to the postsynaptic receptors of the muscle cell
membrane, signaling the muscle to contract.
Clinical significance
Damage to lower motor neurons,
amyotrophic lateral sclerosis (ALS) are all pathologies associated with lower motor neuron dysfunction.[6][7]
See also
References
- ^ Fletcher, T.F. "Clinical Neuroanatomy Guide". Retrieved 8 November 2013.
- PMID 17438014.
- ISBN 978-0-7817-6003-4.)
{{cite book}}: CS1 maint: multiple names: authors list (link - ^ Saim, Muhammad (17 April 2012). "Upper and Lower Motor Neurons". Retrieved 8 November 2013.
- )
- PMID 20386632.
- S2CID 25844355.