The control systems: nervous and endocrine
Nick Draper, Helen Marshall in Exercise Physiology, 2014
Neurons vary greatly in both length and diameter depending on their function within the body. Some nerve cells, such as those responsible for bringing about muscular contraction of the lower leg and feet, are over one metre in length. Like other cells within the body, the cell body (soma or perikaryon) comprises of a cell membrane, a nucleus and cytoplasm. The plasma membrane of the cell body and dendrites is called the neurilemma. However, the cell membrane of the axon is usually referred to as the axolemma because the function of axons necessitates differences in structure when compared with the rest of the cell. In a similar way the cytoplasm of the cell body is known as neuroplasm whereas that in the axon is called axoplasm. The cytoplasm of neurons contains many organelles common to other cells, such as lysosomes, ribosomes, mitochondria and a Golgi apparatus. In addition to generalised organelles, they contain some neuron-specific components, such as neurofibrils, neuron-specific microtubules and Nissl bodies. Neurofibrils are comprised of protein filaments and are designed to maintain the structure of the cell body. The neuron-specific microtubules provide a transport structure through which substances pass between the cell body and the axon. Nissl bodies are small rough endoplasmic reticulum structures that are responsible for synthesising proteins to be used for growth and repair.
Nerve
Manoj Ramachandran, Tom Nunn in Basic Orthopaedic Sciences, 2018
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).
Principles of cognitive rehabilitation in TBI: An integrative neuroscience approach
Mark J. Ashley, David A. Hovda in Traumatic Brain Injury, 2017
Studies with animal models and human autopsy findings have been used to study the pathophysiology of DAI.21,23 Although the discussion on DAI has focused traditionally on myelinated axons, more recently there is evidence supporting the involvement of fine fiber unmyelinated axons (like the cells found in the splenium of the corpus callosum).22 Hence, focusing only on myelinated axons may underestimate the full effect of axonal damage. Animal models simulated severe injuries resulting in stretching or compressing of long tract axons with maximal stretching or compression at focal points on the axons’ length. At 12–24 hours postinjury, swollen axoplasmic masses, called retraction balls, formed and detached from more distal axonal segments. In less severe injuries, focal alterations of axolemma can lead to progressive changes and a cascade of electrochemical events interfering with axonal transport (anterograde and retrograde), focal axonal swelling, and detachment from the distal axonal segment.
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
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