Nowadays, Lower motor neuron is a topic that has gained great relevance in our society. Since its appearance, it has generated different opinions and debates in various areas. The impact of Lower motor neuron is not limited to a single area, but extends to multiple aspects of daily life. That is why it is crucial to thoroughly analyze this issue, understanding its implications and consequences. In this article, we will explore in detail the importance of Lower motor neuron and its influence in different contexts, with the aim of promoting a broad and critical vision of this phenomenon.
Lower motor neuron | |
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Identifiers | |
FMA | 84632 |
Anatomical terms of neuroanatomy |
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). Many voluntary movements rely on spinal lower motor neurons, which innervate skeletal muscle fibers and act as a link between upper motor neurons and muscles. Cranial nerve lower motor neurons also control some voluntary movements of the eyes, face and tongue, and contribute to chewing, swallowing and vocalization. Damage to the lower motor neurons can lead to flaccid paralysis, absent deep tendon reflexes and muscle atrophy.
Lower motor neurons are classified based on the type of muscle fiber they innervate:
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.
Damage to lower motor neurons, lower motor neuron lesions (LMNL) cause muscle wasting (atrophy), decreased strength and decreased reflexes in affected areas. 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.
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