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When a peripheral fiber is severed, the myelin sheath provides a track along which regrowth can occur. However, the myelin layer does not ensure a perfect regeneration of the nerve fiber. Some regenerated nerve fibers do not find the correct muscle fibers, and some damaged motor neurons of the peripheral nervous system die without regrowth ...
The optimal ratio of axon diameter divided by the total fiber diameter (which includes the myelin) is 0.6. [24] Oligodendrocytes in rat cerebellum stained with antibody to myelin basic protein in red and for DNA in blue. Two oligodendrocyte cell bodies are clearly visible as well as several myelinated axons.
Schwann cells or neurolemmocytes (named after German physiologist Theodor Schwann) are the principal glia of the peripheral nervous system (PNS). Glial cells function to support neurons and in the PNS, also include satellite cells, olfactory ensheathing cells, enteric glia and glia that reside at sensory nerve endings, such as the Pacinian corpuscle.
The protein composition of neurofilaments varies widely across different animal phyla. Most is known about mammalian neurofilaments. Historically, mammalian neurofilaments were originally thought to be composed of just three proteins called neurofilament protein NF-L (low molecular weight; NF-L), NF-M (medium molecular weight; NF-M) and NF-H (high molecular weight; NF-H).
Immature oligodendrocyte: Sometimes referred to as premyelinating oligodendrocytes, these cells extend "pioneer processes" which contact axons and anchor premyelinating oligodendrocytes to neurons such that they are poised to commence myelinogenesis in response to axonal signals. These pioneer processes grow longitudinally along their target axons.
The nodes are primarily composed of sodium and potassium voltage-gated ion channels; CAMs such as neurofascin-186 and NrCAM; and cytoskeletal adaptor proteins such as ankyrin-G and spectrinβIV. [4] Many vertebrate axons are surrounded by a myelin sheath, allowing rapid and efficient saltatory ("jumping") propagation of action
Alpha motor neurons are distinct from gamma motor neurons, which innervate intrafusal muscle fibers of muscle spindles. While their cell bodies are found in the central nervous system (CNS), α motor neurons are also considered part of the somatic nervous system —a branch of the peripheral nervous system (PNS)—because their axons extend ...
For example, when mutations occur in dynein, a motor protein that is crucial in maintaining the uniform orientation of axonal neurotubules, the neurotubule polarity in axon becomes mixed. [10] Dendritic proteins are mis-trafficked into axons as a result. [11] For unpolarized neurons, the neurites contain 80% neurotubules with plus (+) end ...