| 词条 | Lower motor neuron |
| 释义 |
| Name = Lower motor neuron | Image = | Caption = | Width = | Precursor= | Artery = | Vein = | Nerve = | Lymph = Lower motor neurons (LMNs) are motor neurons located in either the anterior grey column, anterior nerve roots (spinal lower motor neurons) or the cranial nerve nuclei of the brainstem and cranial nerves with motor function (cranial nerve lower motor neurons).[1] All voluntary movement relies on spinal lower motor neurons, which innervate skeletal muscle fibers and act as a link between upper motor neurons and muscles.[2][3] Cranial nerve lower motor neurons control 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. ClassificationLower motor neurons are classified based on the type of muscle fiber they innervate:
Physiology{{See also|Skeletal muscle#Cellular physiology and contraction|Muscle contraction#Skeletal muscle}}Glutamate released from the upper motor neurons triggers depolarization in the lower motor neurons in the anterior grey column, which in turn causes an action potential to propagate the length of the axon to the neuromuscular junction where acetylcholine is released to carry the signal across the synaptic cleft to the postsynaptic receptors of the muscle cell membrane, signaling the muscle to contract. Clinical significance{{main|lower motor neuron lesion}}Damage to lower motor neurons, lower motor neuron lesions (LMNL) cause muscle wasting, decreased strength and decreased reflexes in affected areas. Damage to the upper motor neuron causes muscle atrophy with long standing lesion. These findings are in contrast to findings in upper motor neuron lesions. LMNL is indicated by abnormal EMG potentials, fasciculations, paralysis, weakening of muscles, and neurogenic atrophy of skeletal muscle. Bell's Palsy, Bulbar palsy, Poliomyelitis and Amyotrophic lateral sclerosis (ALS) are all pathologies associated with lower motor neuron dysfunction.[5][6] See also
References1. ^{{cite web|last=Fletcher|first=T.F.|title=Clinical Neuroanatomy Guide|url=http://vanat.cvm.umn.edu/mLocLesGui/clinAnat.html|accessdate=8 November 2013}} {{Nervous tissue}}{{Use dmy dates|date=April 2017}}2. ^{{cite journal|last=Burke|first=Robert|title=Sir Charles Sherrington's The integrative action of the nervous system: a centenary appreciation|journal=Brain|year=2007|volume=130|issue=4|pages=887–894|pmid=17438014|url=http://brain.oxfordjournals.org/content/130/4/887.full|accessdate=8 November 2013|doi=10.1093/brain/awm022}} 3. ^{{cite book|last=Bear, Connors, Paradiso|title=Neuroscience: Exploring the Brain|year=2007|publisher=Lippincott Williams & Wilkins|isbn=978-0-7817-6003-4|pages=426–432}} 4. ^{{cite web|last=Saim|first=Muhammad|title=Upper and Lower Motor Neurons|url=http://www.slideshare.net/saim_18/upper-and-lower-motor-neuron|accessdate=8 November 2013}} 5. ^{{cite journal|last=Sanders|first=RD|title=The Trigeminal (V) and Facial (VII) Cranial Nerves: Head and Face Sensation and Movement.|journal=Psychiatry (Edgmont)|date=Jan 2010|pmid=20386632|volume=7|issue=1|pages=13–6|pmc=2848459}} 6. ^{{cite journal|author1=Van den Berg |author2=et. al |title=The spectrum of lower motor neuron syndromes|journal=J. Neurol.|date=November 2003|pmid=14648143|doi=10.1007/s00415-003-0235-9|volume=250|issue=11|pages=1279–92}} 2 : Somatic motor system|Efferent neurons |
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