Motor nerve

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Motor nerve of ox
Motor nerve
Details
Identifiers
Latinnervus motorius
FMA5867
Anatomical terms of neuroanatomy

A motor nerve is a

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] The vast majority of nerves contain both sensory and motor fibers and are therefore called mixed nerves.[4]

Structure and function

Motor nerve fibers

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

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]

Beta

muscle spindles. These nerves are responsible for signaling slow twitch muscle fibers.[8]

Gamma

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]

See also

References

  1. ^
    S2CID 207407321
    .
  2. Science Direct
    . Retrieved 2021-02-19.
  3. ^ "Motor Nerve - an overview". Science Direct. Retrieved 2021-02-19.
  4. PMID 29553367
    .
  5. ^ Purves, Dale (2012). Neuroscience 5th Edition. Sunderland, Mass.
  6. PMID 29390312
    .
  7. ^
    OCLC 56661571.{{cite book}}: CS1 maint: multiple names: authors list (link
    )
  8. ^
    OCLC 18350581
    .
  9. ^ "Motor Neuron Disease".
  10. ^ "Peripheral Nerve Disorders - Columbia Neurosurgery". Columbia Neurosurgery. Retrieved 2018-03-26.
  11. PMID 27094884
    .
  12. PMID 29358957
    .
  13. ^ "Nerve Injuries - OrthoInfo - AAOS". Retrieved 2018-03-26.
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