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Neuromuscular Physiology
Published in Michael H. Stone, Timothy J. Suchomel, W. Guy Hornsby, John P. Wagle, Aaron J. Cunanan, Strength and Conditioning in Sports, 2023
Michael H. Stone, Timothy J. Suchomel, W. Guy Hornsby, John P. Wagle, Aaron J. Cunanan
A whole muscle consists of about 85% muscle fibers and approximately 15% connective tissue. The connective tissue organizes the muscle and provides shaped. Connective tissue is composed of a ground substance, collagen, reticular and elastin fibers in various proportions. The proportions of these constituents depend upon a number of factors including the muscle’s function, training, and nutritional factors. Importantly, the connective tissue is largely responsible for force transmission (Ft). Indeed, forces created at the sarcomere level are largely transmitted to the lever system (bones) by a series of connective tissues terminating in the tendon-bone interface. The degree of elasticity and distensibility of the connective tissue (and the muscle) helps to ensure that the tension developed by the muscle is efficiently transmitted and that the muscle will return to its original shape after being shortened or stretched. So, it is the connective tissue of muscle that provides a conceptual framework for the series and parallel elastic components within a muscle. As a result of passive stretching or active contraction the initial tension created is primarily a result of the elastic properties of the connective tissue. During a shortening or lengthening contraction, the muscle cannot develop force or perform work against a resistance until the elastic components are stretched to the point that muscle tension and the resistance (load) are in equilibrium.
Fascial Anatomy
Published in David Lesondak, Angeli Maun Akey, Fascia, Function, and Medical Applications, 2020
The fibers provide the mechanical properties of the connective tissue. The fibers have the power to transfer force generated by muscle cells, and they seem to get stronger and thicker when tensional stress is applied.12,13 There are two types of fibers in connective tissue: collagen fibers and elastic fibers. Collagen is the main structural protein in the connective tissue. The name collagen comes from the Greek κόλλα (kólla), meaning “glue”, and the suffix -γέν, -gen, denoting “producing”. A collagen fiber’s lifespan varies depending on its collagen types. To describe the length of the life of a collagen fiber, researchers use the term “turnover time” to indicate a biogeochemical cycle. It is a measure of how long it takes to fill or empty a particular nutrient reservoir. The human collagen turnover time has been estimated from 300 to 500 days. In animal studies, the rate differs. For instance, rat collagen fibers turnover time varies even more: intestine 20 days, liver 30 days, muscles 50 days, tendon 110 days.14 The metabolism of the rat is much faster than the human (estimated seven to ten times), therefore those findings are not comparable to human subjects.15
The Musculoskeletal System and Its Disorders
Published in Walter F. Stanaszek, Mary J. Stanaszek, Robert J. Holt, Steven Strauss, Understanding Medical Terms, 2020
Walter F. Stanaszek, Mary J. Stanaszek, Robert J. Holt, Steven Strauss
Systemic lupus erythematosus is diagnosed by presentation of a number of clinical symptoms, most commonly arthralgia (arth = joint, algia = pain) and arthritis. Laboratory tests show abnormal ANA titer, positive LE cell test. Several different drugs are utilized in the treatment of systemic lupus erythematosus. Aspirin and the NSAIDs are used to manage arthralgias or synovitis (inflammation of the synovium), pleurisy, headache, and low-grade fever. The antimalarial agent hydroxychloroquine is effective in treating arthralgias, arthritis, and skin disease. Corticosteroids are used to control the inflammatory response. Connective tissue disorders are treated by rest and exercise, physical and occupational therapy, heat, supportive or rehabilitative devices, education, nutrition, and orthopedic surgery.
Anatomic variations of the human falx cerebelli and its association with occipital venous sinuses
Published in British Journal of Neurosurgery, 2021
Safiye Çavdar, Bilgehan Solmaz, Özgül Taniş, Orhan Ulas Guler, Hakkı Dalçık, Evren Aydoğmuş, Leyla Altunkaya, Erdoğan Kara, Hızır Aslıyüksek
Falx cerebelli, is composed of fibroelastic, dense irregular connective tissue. The connective tissue consisted of cells predominantly of fibroblast which produced the ground substance and collagen fibers. Additionally, the connective tissue contained sensory nerve endings and blood vessels. The arterioles were composed of 1–2 layers of smooth muscle cells in the tunica media and the venules were composed of a single layer of endothelium with many erythrocytes in their lumens (Figure 10a). Furthermore, a large number of lymphatic vessels appeared to be undulated with a single layer of endothelium and a subendothelial layer (Figure 10b). Extravagated lymphocytes surrounding the lymphatic vessels were observed (Figure 10b). Near the vessels, a peripheral nerve characteristically formed a round bundle of nerve processes surrounded by connective tissue sheath perineurium was detected (Figure 10a).
Bilaminar Structure of the Human Optic Nerve Sheath
Published in Current Eye Research, 2020
Alan Le, Andrew Shin, Joseph Park, Vadims Poukens, Joseph L. Demer
While medial rectus muscle force acts across a broad tendon insertion,45 reaction force to it when the globe is tethered in adduction is concentrated on the smaller ON canal and peripapillary sclera. Presumably, reaction force is concentrated on the ON sheath to protect the more delicate ON within it. In this study, we examined the structural characteristics of the human ON sheath, emphasizing its dimensions, structure, and elastin fiber characteristics due to the mechanical properties of elastin under low strain mechanical loading.46 Elastin endows tissue with reversible extensibility and hence is abundant in tissues that endure repetitive mechanical stress, such as skin, lung, arteries, and cartilage.46–50 In the orbital connective tissue system, elastin fibers are preferentially located in tissues that experience repetitive mechanical loading by the extraocular muscles.51 Elastin in canine carotid artery was shown to resist both circumferential and longitudinal loads, whereas collagen only bears circumferential loads.52 In mouse aorta, exposure to elastase resulted in decrease of axial stretch of vessel walls.49
Identification of Key Pathways and Genes in L4 Dorsal Root Ganglion (DRG) After Sciatic Nerve Injury via Microarray Analysis
Published in Journal of Investigative Surgery, 2020
He Zhao, Li-Jun Duan, Qing-Ling Sun, Yu-Shan Gao, Yong-Dong Yang, Xiang-Sheng Tang, Ding-Yan Zhao, Yang Xiong, Zhen-Guo Hu, Chuan-Hong Li, Si-Xue Chen, Tao Liu, Xing Yu
Peripheral nerve injury (PNI) may have devastating consequences. The outcome of injury is determined by the amount of cellular damage, variables which include the site of the lesion, the degree of disruption of the connective-tissue sheaths that surround the nerve, and the extent of associated injuries. After PNI, inevitable neuropathic pain including acrodynia, hyperalgesia, and spontaneous pain occurs due to stimulation of adverse insults containing the protrusion of a lumbar intervertebral disc, nerve compression, and neoplasm invasion in dorsal root ganglia (DRG) or radix spinalis.1,2 DRG mainly consists of the pseudounipolar neuron, transmitting physi-, path-ology sensory signals from the exter-, inter-, propri-oceptor via neuronal cell body to the spinal dorsal horn. As we know, injury to the peripheral nervous system will definitely contribute to “Wallerian degeneration”3,4 which is progress in that the distal axon of injury site progressively degenerates with the breakdown of both axons and myelin sheath. Notably, DRG as the modulatory locus participate in neuropathic pain and nerve regeneration and may become the vital therapeutic target. In brief, the molecular mechanism of neuropathic pain and nerve regeneration is still a worthy topic, and we aim to explore the central genes and pathways in DRG after injury through bioinformatics analysis.