The history provides clinical clues. In most myopathies, weakness is proximal, affecting movements of the hips, thighs, shoulders, and upper arms. Typically, these patients have difficulty climbing stairs, arising from…
Type I fibers are adept at utilizing the aerobic oxidative pathway for long periods of time. As shown by electron microscopy, they contain large numbers of mitochondria, which confer a…
CARBOHYDRATE METABOLISM Blood glucose enters the muscle fiber through a specialized muscle-specific glucose transporter. It is then phosphorylated to glucose-6-phosphate and undergoes glycolysis. Glucose-6-phosphate is also derived from degradative phosphorylation…
Measurement of the effects of stimulation frequency is possible under similar conditions of isometric contraction. Given that there is all-or-nothing activation and contraction of fibers within a motor unit after…
T tubules are specialized invaginations of the sarcolemma, with which it is continuous at multiple points. T tubules run transverse to the muscle fibers themselves and the sarcolemma and encircle…
Troponin molecules also run the course of the thin filament but occur as complexes bound at regular intervals. Three components comprise troponin: TnI, TnT, and TnC. TnI is an inhibitory…
Botulism is a rare life-threatening neuroparalytic syndrome caused by an anaerobic organism, Clostridium botulinum, that produces an extremely potent neurotoxin. C. botulinum spores are heat resistant; when they germinate, these…
Each muscle fiber is also surrounded by a basal lamina, or basement membrane. Lying under the basement membrane are specialized cells referred to as satellite cells. Satellite cells are derived…
CMSs are caused by defects affecting the presynaptic, synaptic basal lamina–associated, and postsynaptic regions of the neuromuscular junction. Inheritance is autosomal recessive, except in the dominantly inherited slow-channel CMS. While…
Approximately 50% of LEMS patients have a small cell lung cancer (SCLC), often not clinically evident at the inception of neuromuscular symptoms. Presumably, the immune response leading to LEMS begins…
