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Muscle and Nerve Histology
Published in Maher Kurdi, Neuromuscular Pathology Made Easy, 2021
Axons arise from the cell body at axon hillocks where the thin dendritic process extends. Each axon is surrounded by a plasma membrane called axolemma and contains nuclei and axoplasm; the latter has no ribosomes or rough endoplasmic reticulum (RER). The axolemma forming the myelin sheath is referred to as myelinated axon. Axons lacking myelin sheaths are called unmyelinated axons or Remak fibers. The myelinated axon (1–20 μm in diameter) is longer than the unmyelinated axon (0.2–2 μm in diameter). The unmyelinated fibers are always multiple, sensory, and characterized ultrastructurally by the presence of a single basal lamina surrounding the entire fiber. In the sural nerve, the ratio of myelinated to unmyelinated fibers is 1:4.
The Peripheral Nerves
Published in Bernard J. Dalens, Jean-Pierre Monnet, Yves Harmand, Pediatric Regional Anesthesia, 2019
Bernard J. Dalens, Jean-Pierre Monnet, Yves Harmand
Myelinated fibers consist of axons of nerve cells and are surrounded by two sheaths, the myelin sheath and the Schwann cell sheath. The myelin sheath presents regular interruptions called nodes of Ranvier (Figure 1.59). The myelin sheath is separated from the relevant axons by a very thin membrane, the axolemma, which is part of the neuron plasma membrane that possesses special properties. Between consecutive nodes, the myelin sheath is regularly divided by oblique clefts known as Schmidt-Lantermann clefts (such clefts do not exist in myelinated fibers of the central nervous system).
Nerve
Published in Manoj Ramachandran, Tom Nunn, Basic Orthopaedic Sciences, 2018
Mike Fox, Caroline Hing, Sam Heaton, Rolfe Birch
Neurons specialize in sending and receiving chemically-mediated electrical signals. The functional unit of a nerve is the neuron; it has a cell body (perikaryon) and an axon. The axolemma (cell membrane) encloses the axoplasm (cytoplasm). The cell body contains all the subcellular organelles found in a typical cell but is specialized to provide high levels of protein synthesis, by having densely packed ribosomes on the rough endoplasmic reticulum. Dendrites are extensions of the cell body and receive signals from other neurons. Each neuron generally has a single axon arising from the cell body that typically conducts impulses away from the cell body. This may be encapsulated in a myelin sheath (Figure 11.1).
Neurological complications of Zika virus infection
Published in Expert Review of Anti-infective Therapy, 2018
Electrophysiological studies performed in GBS cases in French Polynesia showed a pattern of acute motor axonal neuropathy (AMAN) [57]. Both amplitude and conduction velocity of sensitive nerve action potentials were normal. Nerve conduction studies detected prolonged motor distal latencies, which disappeared during follow-up, and a significant reduction in distal motor action potentials. Authors proposed the term ‘axonal’ involvement was not associated with axonal degeneration but rather with transitory and reversible axolemma dysfunction.
Neuroprotective potential of Spirulina platensis on lesioned spinal cord corticospinal tract under experimental conditions in rat models
Published in Ultrastructural Pathology, 2019
Dauda Abdullahi, Azlina Ahmad Annuar, Junedah Sanusi
The ultrastructure of the corticospinal tract axon in the sham (laminectomy) group revealed a typical profile of granular axons with definitive axonal cytoskeletal structure (microtubules and neurofilament), and, the plasma membrane of the axon (axolemma) are normally apposed to inner lamellae of the myelin sheath, on Day-28 (Figure 5a).
Promptly and appropriately treat SARS-CoV-2– related Guillain-Barre syndrome in a gravida to improve the outcome
Published in Baylor University Medical Center Proceedings, 2023
The difference between AMAN and AIDP is due to different targets of antibody attack. In AMAN, antibodies are deposited on the nodal and internodal axolemma, whereas in AIDP antibodies are deposited on the myelin sheath.3