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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
Sarcomeres contain various elements and a variety of different proteins. Within the sarcomere are myofibrils (protein arrays), which are largely constructed from the contractile proteins (actin and myosin), along with smaller amounts of regulatory and stabilizing/structural proteins. Approximately 80% of the myofibrillar protein content consists of actin and myosin (80). Myosin is the most prominent myofibrillar protein making up about 60% to 70% of the protein content. Myosin is relatively large weighing about 500 kD and has a relatively high viscosity. Actin makes up approximately 20% to 25% of the myofibrils protein content and has a low viscosity weighing about 75 kD. Myosin molecules, which are about 150 nm long, consist of two heavy chains with long tails wrapped in an alpha-helix connected to two pear-shaped heads (Figure 1.9).
Functional Anatomy
Published in James Crossley, Functional Exercise and Rehabilitation, 2021
Skeletal muscle is composed of many individual muscle fibers wrapped together in bundles. Connective tissue known as fascia covers each of these bundles. The outer layer that covers the whole muscle is called the epimysium. The epimysium runs into tendon of the muscle that attaches and transmits force to the bone. Muscles attach to bone proximally (origin) and distally (insertion). Origin – muscle attachment that is generally more proximal and moves the leastInsertion – muscle attachment that is generally more distal and moves the most Under the epimysium we see bundles of muscle fibers known as the fascicles, wrapped in fascia called the perimysium. Each muscle fiber is wrapped in a connective tissue called the endomysium. Each muscle fiber forms the building blocks of muscle called myofibrils.
Energy Demand of Muscle Machines
Published in Peter W. Hochachka, Muscles as Molecular and Metabolic Machines, 2019
For many years, it has been known that all vertebrate skeletal muscles display a striated appearance when examined under the light microscope. Such muscles consist of cells, each of which is surrounded by an electrically excitable membrane called the sarcolemma. A muscle cell contains many parallel myofibrils, each about 1 μm in diameter.
Circadian regulation of cardiac muscle function and protein degradation
Published in Chronobiology International, 2023
Proteostasis, including protein synthesis, processing/folding and degradation, is an important cellular mechanism in cardiac muscles (Henning and Brundel 2017; McLendon and Robbins 2015). Compared with non-muscle cells, cardiac muscles are terminally differentiated, must contract throughout lifetime, require robust metabolic/stress responses and involve specialized cellular machineries for electric conductance. The structural and functional unit of striated muscles, including both cardiac and skeletal muscles, is the sarcomere (Martin and Kirk 2020; Ono 2010), which is highly conserved throughout from worms to mammals. Sarcomeres line up sequentially, and tied together by a complex protein assembly called Z-disc to form contractible myofibrils, which in turn are bound in bundles to form cardiomyocytes. The sarcomere consists mainly of the myosin thick filaments and actin thin filaments, with a large number of associated structural and regulatory proteins. Given the heart is the first organ to be formed after birth and must continuously function until death, and that cardiomyocytes are post-mitotic, protein quality control at the sarcomere plays a particularly important role in cardiac proteostasis (Henning and Brundel 2017; Martin and Kirk 2020). Of particular importance is protein degradation mechanisms to remove misfolded or faulty proteins.
Effects of Trans-Cinnamaldehyde on Reperfused Ischemic Skeletal Muscle and the Relationship to Laminin
Published in Journal of Investigative Surgery, 2021
Esra Pekoglu, Belgin Buyukakilli, Cagatay Han Turkseven, Ebru Balli, Gulsen Bayrak, Burak Cimen, Senay Balci
Ultrastructural changes of EDL skeletal muscle tissues were evaluated by a transmission electron microscope. EDL muscle cells were found to have normal morphological properties in the control group and treatment (IR + TCA) group. It was determined that the myofibrils in sarcoplasm had a regular sequence and that the sarcomere structure was protected. Also it was observed that the mitochondrion located between the myofibrils, the sarcoplasmic reticulum (SR) cisternae and other organelles were in a regular structure (Figure 6A,B). EDL muscle cells were generally found to have normal morphological properties in the group with I-R injury (IR + SF) (Figure 7A). Moreover, enlargement of SR cisternae (Figure 7B) and thinning of myofibrils (Figure 7C) were observed in some cells in the IR + SF group.
Massively elevated creatine kinase levels in antihistamine-induced rhabdomyolysis
Published in Baylor University Medical Center Proceedings, 2020
Karan N. Ramakrishna, Amish Shah, Carlos D. Martinez-Balzano
The etiology of rhabdomyolysis can be broadly categorized into traumatic and nontraumatic causes (Table 2). Drugs and toxins are a significant contributor to the incidence of nontraumatic rhabdomyolysis.2 Diphenhydramine and other antihistamines are among the most commonly available over-the-counter sleep aids in the United States. A number of cases of rhabdomyolysis induced by antihistamines have been reported.5–10 Both doxylamine5,6 and diphenhydramine7–9 have been implicated in these cases. It is postulated that antihistamines alter sarcolemmal permeability, causing leakage of intracellular contents and impairment of Na-K ATPase pumps and ATP-dependent calcium channels, causing intracellular calcium accumulation. These mechanisms result in excessive myofibril contraction and impairment of energy-dependent processes leading to myocyte injury and death.1,7