These contractile elements are virtually identical to skeletal muscle. Without sufficient dystrophin, muscle contractions cause the sarcolemma to tear, causing an influx of Ca ++, leading to cellular damage and muscle fiber degradation. Failure of chromosomes to separate during mitosis or meiosis will result in an incorrect number of chromosomes in daughter cells. The parts of the A band that abut the I bands are occupied by both actin and myosin filaments (where they interdigitate as described above). Smooth muscle cells' myofibril arrangement is different than cardiac and skeletal muscle cells, found in great numbers (100's to 1000's per cell) in the myocyte; make up 50-80% of the cell volume; used for contraction. Tropomyosin is a protein that winds around the chains of the actin filament and covers the myosin-binding sites to prevent actin from binding to myosin. They result from membranes of adjacent myocytes being very close together, and form a kind of glue between cells. Study with Quizlet and memorize flashcards containing terms like Which muscle does not contain myofibrils?, Which muscle cells have desmosomes and gap-junctions?, What are the main contractile proteins of the thick and thin filament in a sarcomere called? This may be more of a factor in brief, intense muscle output rather than sustained, lower intensity efforts. The spindle fibers, which are formed by the cell as mitosis progresses, are used to attach to chromosomes, align them down the middle of the cell, and pull chromosomes apart into their identical individual chromatids which will end up in separate cells. Watch this video to learn more about the role of calcium. It is made up of a plasma membrane and an outer layer of polysaccharide material that contains numerous thin collagen fibrils. 1. B) most forms do not appear to be inherited. The T-tubule is present in this area. -forms a weblike network surrounding the myofibrils With no further ATP production possible, there is no ATP available for myosin heads to detach from the actin-binding sites, so the cross-bridges stay in place, causing the rigidity in the skeletal muscles.

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