Alpha Motor Neuron

A neurons cell type of the human nervous system.

Large lower motor neuron whose axon drives skeletal muscle contraction; its degeneration or dysfunction is central to ALS and spinal muscular atrophy.

Function

Final common pathway for voluntary and reflexive skeletal muscle contraction; activates extrafusal muscle fibres at the neuromuscular junction via quantal acetylcholine release.

Morphology

Large multipolar soma with an extensive dendritic tree; among the largest neurons in the CNS, with a myelinated axon exiting via the ventral root.

Specification

  • Neurotransmitter: Acetylcholine (ACh)
  • Co-transmitters: CGRP (peptide cotransmitter/modulator; subtype- and state-dependent)
  • Receptors: Glutamate; GABA; Glycine
  • Location: Spinal cord ventral (anterior) horn; brainstem motor nuclei
  • Projections: Extrafusal muscle fibers
  • Firing: Phasic; Tonic
  • Markers: ChAT (CHAT); VAChT (SLC18A3); CHT1 (SLC5A7); ISL1/ISL2 and MNX1/HB9 (developmental identity); SMI-32 and NeuN (supporting/general)
  • Developmental origin: Neural tube (Ventral)
  • Disease: Amyotrophic lateral sclerosis (ALS); spinal muscular atrophy (SMA)
  • Cell Ontology: CL:0008038

References

  1. Podraza LC & Tadi P (2023). Neuroanatomy, Motor Neuron.. StatPearls [Internet] PMID 32119503
  2. Keinath MC, Prior DE, & Prior TW (2021). Spinal Muscular Atrophy: Mutations, Testing, and Clinical Relevance.. The application of clinical genetics 14 PMID 33531827
  3. DEL CASTILLO J & KATZ B (1954). Quantal components of the end-plate potential.. The Journal of physiology 124 PMID 13175199

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