A motor nerve is a nerve that transmits motor signals from the central nervous system (CNS) to the muscles of the body. This is different from the motor neuron, which includes a cell body and branching of dendrites, while the nerve is made up of a bundle of axons. Motor nerves act as efferent nerves which carry information out from the CNS to muscles, as opposed to afferent nerves (also called sensory nerves), which transfer signals from sensory receptors in the periphery to the CNS.[1] Efferent nerves can also connect to glands or other organs/issues instead of muscles (and so motor nerves are not equivalent to efferent nerves).[2][3] In addition, there are nerves that serve as both sensory and motor nerves called mixed nerves.[4]
Motor nerve fibers transduce signals from the CNS to peripheral neurons of proximal muscle tissue. Motor nerve axon terminals innervate skeletal and smooth muscle, as they are heavily involved in muscle control. Motor nerves tend to be rich in acetylcholine vesicles because the motor nerve, a bundle of motor nerve axons that deliver motor signals and signal for movement and motor control.[5] Calcium vesicles reside in the axon terminals of the motor nerve bundles. The high calcium concentration outside of presynaptic motor nerves increases the size of end-plate potentials (EPPs).[6]
Protective tissues
Within motor nerves, each axon is wrapped by the endoneurium, which is a layer of connective tissue that surrounds the myelin sheath. Bundles of axons are called fascicles, which are wrapped in perineurium. All of the fascicles wrapped in the perineurium are wound together and wrapped by a final layer of connective tissue known as the epineurium. These protective tissues defend nerves from injury, pathogens and help to maintain nerve function. Layers of connective tissue maintain the rate at which nerves conduct action potentials.[7]
Motor nerves wrapped in endoneurium
Spinal cord exit
Most motor pathways originate in the motor cortex of the brain. Signals run down the brainstem and spinal cord ipsilaterally, on the same side, and exit the spinal cord at the ventral horn of the spinal cord on either side. Motor nerves communicate with the muscle cells they innervate through motor neurons once they exit the spinal cord.[1][7]
Motor nerve types
Motor nerves can vary based on the subtype of motor neuron they are associate with.[8]
Alpha
Alpha motor neurons target extrafusal muscle fibers. The motor nerves associated with these neurons innervate extrafusal fibers and are responsible for muscle contraction. These nerve fibers have the largest diameter of the motor neurons and require the highest conduction velocity of the three types.[8]
Gamma motor neurons, unlike alpha motor neurons, are not directly involved in muscle contraction. The nerves associated with these neurons do not send signals that directly adjust the shortening or lengthening of muscle fibers. However, these nerves are important in keeping muscle spindles taut.[8]
Neurodegeneration
Motor neural degeneration is the progressive weakening of neural tissues and connections in the nervous system. Muscles begin to weaken as there are no longer any motor nerves or pathways that allows for muscle innervation. Motor neuron diseases can be viral, genetic or be a result of environmental factors. The exact causes remain unclear, however many experts believe that toxic and environmental factors play a large role.[9]
Neuroregeneration
Neural stem cells seen in green
There are problems with neuroregeneration due to many sources, both internal and external. There is a weak regenerative ability of nerves and new nerve cells cannot simply be made. The outside environment can also play a role in nerve regeneration. Neural stem cells (NSCs), however, are able to differentiate into many different types of nerve cells. This is one way that nerves can "repair" themselves. NSC transplant into damaged areas usually leads to the cells differentiating into astrocytes which assists the surrounding neurons. Schwann cells have the ability to regenerate, but the capacity that these cells can repair nerve cells declines as time goes on as well as distance the Schwann cells are from site of damage.[10][11][12][13]
^ abSlater, Clarke R. (2015-11-01). "The functional organization of motor nerve terminals". Progress in Neurobiology. 134: 55–103. doi:10.1016/j.pneurobio.2015.09.004. ISSN 0301-0082. PMID 26439950. S2CID 207407321.
^Jang, Sung Ho; Lee, Han Do (December 2017). "Gait recovery by activation of the unaffected corticoreticulospinal tract in a stroke patient: A case report". Medicine. 96 (50): e9123. doi:10.1097/MD.0000000000009123. ISSN 0025-7974. PMC5815724. PMID 29390312.
^ abC., Guyton, Arthur (2006). Textbook of medical physiology. Hall, John E. (John Edward), 1946- (11th ed.). Philadelphia: Elsevier Saunders. ISBN978-0721602400. OCLC 56661571.
^ abcdGray, Henry (1989). Gray's anatomy. Williams, Peter L. (Peter Llewellyn), Gray, Henry, 1825-1861. (37th ed.). Edinburgh: C. Livingstone. ISBN978-0443041778. OCLC 18350581.
^"Peripheral Nerve Disorders - Columbia Neurosurgery". Columbia Neurosurgery. Retrieved 2018-03-26.
^Gordon, Tessa (2016-05-01). "Nerve Regeneration: Understanding Biology and Its Influence on Return of Function After Nerve Transfers". Hand Clinics. 32 (2): 103–117. doi:10.1016/j.hcl.2015.12.001. ISSN 0749-0712. PMID 27094884.
^Huang, Lixiang; Wang, Gan (2017). "The Effects of Different Factors on the Behavior of Neural Stem Cells". Stem Cells International. 2017: 9497325. doi:10.1155/2017/9497325. ISSN 1687-966X. PMC5735681. PMID 29358957.
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A motor nerve is a nerve that transmits motor signals from the central nervous system CNS to the muscles of the body This is different from the motor neuron which includes a cell body and branching of dendrites while the nerve is made up of a bundle of axons Motor nerves act as efferent nerves which carry information out from the CNS to muscles as opposed to afferent nerves also called sensory nerves which transfer signals from sensory receptors in the periphery to the CNS 1 Efferent nerves can also connect to glands or other organs issues instead of muscles and so motor nerves are not equivalent to efferent nerves 2 3 In addition there are nerves that serve as both sensory and motor nerves called mixed nerves 4 Motor nerve of Ox Motor nerveDetailsIdentifiersLatinnervus motoriusFMA5867Anatomical terms of neuroanatomy edit on Wikidata Contents 1 Structure and function 2 Protective tissues 3 Spinal cord exit 4 Motor nerve types 4 1 Alpha 4 2 Beta 4 3 Gamma 5 Neurodegeneration 6 Neuroregeneration 7 See also 8 ReferencesStructure and function EditMotor nerve fibers transduce signals from the CNS to peripheral neurons of proximal muscle tissue Motor nerve axon terminals innervate skeletal and smooth muscle as they are heavily involved in muscle control Motor nerves tend to be rich in acetylcholine vesicles because the motor nerve a bundle of motor nerve axons that deliver motor signals and signal for movement and motor control 5 Calcium vesicles reside in the axon terminals of the motor nerve bundles The high calcium concentration outside of presynaptic motor nerves increases the size of end plate potentials EPPs 6 Protective tissues EditWithin motor nerves each axon is wrapped by the endoneurium which is a layer of connective tissue that surrounds the myelin sheath Bundles of axons are called fascicles which are wrapped in perineurium All of the fascicles wrapped in the perineurium are wound together and wrapped by a final layer of connective tissue known as the epineurium These protective tissues defend nerves from injury pathogens and help to maintain nerve function Layers of connective tissue maintain the rate at which nerves conduct action potentials 7 Motor nerves wrapped in endoneuriumSpinal cord exit EditMost motor pathways originate in the motor cortex of the brain Signals run down the brainstem and spinal cord ipsilaterally on the same side and exit the spinal cord at the ventral horn of the spinal cord on either side Motor nerves communicate with the muscle cells they innervate through motor neurons once they exit the spinal cord 1 7 Motor nerve types EditMotor nerves can vary based on the subtype of motor neuron they are associate with 8 Alpha Edit Alpha motor neurons target extrafusal muscle fibers The motor nerves associated with these neurons innervate extrafusal fibers and are responsible for muscle contraction These nerve fibers have the largest diameter of the motor neurons and require the highest conduction velocity of the three types 8 Beta Edit Beta motor neurons innervate intrafusal fibers of muscle spindles These nerves are responsible for signaling slow twitch muscle fibers 8 Gamma Edit Gamma motor neurons unlike alpha motor neurons are not directly involved in muscle contraction The nerves associated with these neurons do not send signals that directly adjust the shortening or lengthening of muscle fibers However these nerves are important in keeping muscle spindles taut 8 Neurodegeneration EditMotor neural degeneration is the progressive weakening of neural tissues and connections in the nervous system Muscles begin to weaken as there are no longer any motor nerves or pathways that allows for muscle innervation Motor neuron diseases can be viral genetic or be a result of environmental factors The exact causes remain unclear however many experts believe that toxic and environmental factors play a large role 9 Neuroregeneration Edit Neural stem cells seen in green There are problems with neuroregeneration due to many sources both internal and external There is a weak regenerative ability of nerves and new nerve cells cannot simply be made The outside environment can also play a role in nerve regeneration Neural stem cells NSCs however are able to differentiate into many different types of nerve cells This is one way that nerves can repair themselves NSC transplant into damaged areas usually leads to the cells differentiating into astrocytes which assists the surrounding neurons Schwann cells have the ability to regenerate but the capacity that these cells can repair nerve cells declines as time goes on as well as distance the Schwann cells are from site of damage 10 11 12 13 See also EditEfferent nerve fiber Motor neuron efferent neuron References Edit a b Slater Clarke R 2015 11 01 The functional organization of motor nerve terminals Progress in Neurobiology 134 55 103 doi 10 1016 j pneurobio 2015 09 004 ISSN 0301 0082 PMID 26439950 S2CID 207407321 Efferent Nerve an overview Science Direct Retrieved 2021 02 19 a href Template Cite web html title Template Cite web cite web a CS1 maint url status link Motor Nerve an overview Science Direct Retrieved 2021 02 19 a href Template Cite web html title Template Cite web cite web a CS1 maint url status link Glass Jonathan D 2018 03 19 Neuromuscular Disease Protecting the nerve terminals eLife 7 doi 10 7554 eLife 35664 ISSN 2050 084X PMC 5858932 PMID 29553367 Purves Dale 2012 Neuroscience 5th Edition Sunderland Mass Jang Sung Ho Lee Han Do December 2017 Gait recovery by activation of the unaffected corticoreticulospinal tract in a stroke patient A case report Medicine 96 50 e9123 doi 10 1097 MD 0000000000009123 ISSN 0025 7974 PMC 5815724 PMID 29390312 a b C Guyton Arthur 2006 Textbook of medical physiology Hall John E John Edward 1946 11th ed Philadelphia Elsevier Saunders ISBN 978 0721602400 OCLC 56661571 a b c d Gray Henry 1989 Gray s anatomy Williams Peter L Peter Llewellyn Gray Henry 1825 1861 37th ed Edinburgh C Livingstone ISBN 978 0443041778 OCLC 18350581 Motor Neuron Disease Peripheral Nerve Disorders Columbia Neurosurgery Columbia Neurosurgery Retrieved 2018 03 26 Gordon Tessa 2016 05 01 Nerve Regeneration Understanding Biology and Its Influence on Return of Function After Nerve Transfers Hand Clinics 32 2 103 117 doi 10 1016 j hcl 2015 12 001 ISSN 0749 0712 PMID 27094884 Huang Lixiang Wang Gan 2017 The Effects of Different Factors on the Behavior of Neural Stem Cells Stem Cells International 2017 9497325 doi 10 1155 2017 9497325 ISSN 1687 966X PMC 5735681 PMID 29358957 Nerve Injuries OrthoInfo AAOS Retrieved 2018 03 26 Retrieved from https en wikipedia org w index php title Motor nerve amp oldid 1143929338, wikipedia, wiki, book, books, library,
