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Encyclopedia > Lower motor neuron

Lower motor neurons (LMNs) are the motor neurons connecting the brainstem and spinal cord to muscle fibers, bringing the nerve impulses from the upper motor neurons out to the muscles. A lower motor neuron's axon travels through a foramen and terminates on an effector (muscle). In vertebrates, the term motor neuron (or motoneuron) classically applies to neurons located in the central nervous system (CNS) which project their axons outside the CNS and directly or indirectly control muscles. ... The brain stem is the stalk of the brain below the cerebral hemispheres. ... The Spinal cord nested in the vertebral column. ... A muscle fiber (American usage) or muscle fibre (British usage) is a single cell of a muscle. ... A. A schematic view of an idealized action potential illustrates its various phases as the action potential passes a point on a cell membrane. ... Upper motor neurons are any neurons that carry motor information down to the final common pathway, that is, any neurons that are not directly responsible for stimulating the target muscle. ... For other uses of Muscles, see Muscles (disambiguation). ...


Classification

The axons of lower motor neurons are a type of motor fibers. Lower motor neurons are classified based on the type of muscle fiber they innervate:

Alpha motor neurons (α-MNs) are large lower motor neurons of the brainstem and spinal cord. ... Extrafusal muscle fibers are a class of muscle fiber innervated by alpha motor neurons. ... A top-down view of skeletal muscle A muscle contraction (also known as a muscle twitch or simply twitch) occurs when a muscle fiber generates tension through the action of actin and myosin cross-bridge cycling. ... In the nervous system, gamma motor neurons (γ-MNs) are lower motor neurons that innervate intrafusal muscle fibers. ... Intrafusal fibers are muscle fibers that comprise the muscle spindle. ... A muscle spindle is a specialized muscle structure innervated by both sensory and motor neuron axons. ... // Proprioception (PRO-pree-o-SEP-shun (IPA pronunciation: ); from Latin proprius, meaning ones own and perception) is the sense of the relative position of neighbouring parts of the body. ...

Physiology

Glutamate released from the upper motor neurons triggers depolarization in the lower motor neurons in the ventral horn 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. Glutamate is the anion of glutamic acid. ... In biology, depolarization is the event a cell undergoes when its membrane potential grows more positive with respect to the extracellular solution. ... An axon or nerve fiber, is a long, slender projection of a nerve cell, or neuron, that conducts electrical impulses away from the neurons cell body or soma. ... A neuromuscular junction is the junction of the axon terminal of a motoneuron with the motor end plate, the highly-excitable region of muscle fiber plasma membrane responsible for initiation of action potentials across the muscles surface. ... The chemical compound acetylcholine, often abbreviated as ACh, was the first neurotransmitter to be identified. ... Synapses allow nerve cells to communicate with one another through axons and dendrites, converting electrical signals into chemical ones. ... A simplified, global view of a neuromuscular junction: 1. ...


Consequences of lesions

Damage to lower motor neurons (lower motor neurone lesions) is indicated by abnormal EMG potentials, fasciculations, paralysis, weakening of muscles, and neurogenic atrophy of skeletal muscle. Electromyography (EMG) is a technique for evaluating and recording physiologic properties of muscles at rest and while contracting. ... It has been suggested that this article or section be merged with Twitching. ... Paralysed redirects here. ... Atrophy is the partial or complete wasting away of a part of the body. ...

Bold text == Headline text == minni hi. ... This article is about cellular photoreceptors. ... Hair cells are the sensory cells of both the auditory system and the vestibular system in all vertebrates. ... Taste buds are small structures on the upper surface of the tongue, soft palate, and epiglottis that provide information about the taste of food being eaten. ... Neuroglia of the brain shown by Golgis method. ... Astrocytes (also known collectively as astroglia) are characteristic star-shaped glial cells in the brain. ... Radial glial cells are a pivotal cell type in the developing CNS involved in key developmental processes, ranging from patterning and neuronal migration to their newly described role as precursors during neurogenesis. ... Oligodendrocytes (from Greek literally meaning few tree cells), or oligodendroglia (Greek, few tree glue),[1] are a variety of neuroglia. ... Ependyma is the thin epithelial membrane lining the ventricular system of the brain and the spinal cord canal. ... Microglia cells positive for lectins Microglia are a type of glial cell that act as the immune cells of the Central nervous system (CNS). ... Myelin is an electrically insulating phospholipid layer that surrounds the axons of many neurons. ... White matter is one of the two main solid components of the central nervous system. ... Oligodendrocytes (from Greek literally meaning few tree cells), or oligodendroglia (Greek, few tree glue),[1] are a variety of neuroglia. ... Named after the German physiologist Theodor Schwann, Schwann cells are a variety of neuroglia that mainly provide myelin insulation to axons in the peripheral nervous system of jawed vertebrates. ... Neurolemma (spelled also neurolema, neurilemma and neurilema, and used interchangeably with epineurium) is the insulating myelin layer that surrounds an individual peripheral nerve fiber. ... This article is about anatomy; for the musical group see Nodes of Ranvier (band) Nodes of Ranvier are regularly spaced gaps in the myelin sheath around an axon or nerve fiber. ... The portion of nerve fiber between two Nodes of Ranvier is called an internodal segment (or internode). ... Oblique clefts may be seen in the medullary sheath, subdividing it into irregular portions, which are termed Schmidt-Lanterman incisures (or clefts of schmidt-lanterman, segments of Lantermann, medullary segments. ... Connective tissue is one of the four types of tissue in traditional classifications (the others being epithelial, muscle, and nervous tissue. ... Neurolemma (spelled also neurolema, neurilemma and neurilema, and used interchangeably with epineurium) is the insulating myelin layer that surrounds an individual peripheral nerve fiber. ... In a nerve fiber, the tubular sheath of the funiculi, perineurium, is a fine, smooth, transparent membrane, which may be easily separated, in the form of a tube, from the fibers it encloses; in structure it is made up of connective tissue, which has a distinctly lamellar arrangement. ... The nerve fibers are held together and supported within the funiculus by delicate connective tissue, called the endoneurium. ... A small bundle of fibers, enclosed in a tubular sheath, is called a funiculus; if the nerve is of small size, it may consist only of a single funiculus; but if large, the funiculi are collected together into larger bundles or nerve fascicles, which are bound together in a common... The meninges (singular meninx) are the system of membranes that envelop the central nervous system. ...

  Results from FactBites:
 
Lower motor neuron - Wikipedia, the free encyclopedia (154 words)
Lower motor neurons (LMNs) are the motoneurons connecting the brainstem and spinal cord to muscle fibers, bringing the nerve impulses from the upper motor neurons out to the muscles.
Gamma motor neurons (γ-MNs) innervate intrafusal muscle fibers, which are involved with muscle spindles and the sense of body position.
Damage to lower motor neurons is indicated by abnormal EMG potentials, fasciculations, paralysis, weakening of muscles, and neurogenic atrophy of skeletal muscle.
SPF - Primary Lateral Sclerosis General Information (1410 words)
The disorders are caused primarily by degeneration of the upper motor neurons in the brain and spinal cord.
ALS is caused by degeneration of the lower motor neurons (the nerves that travel from the brainstem and spinal cord out to the muscles) as well as the upper motor neurons.
PLS is caused by degeneration of the upper motor neurons in the brain and spinal cord.
  More results at FactBites »

 
 

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