Muscle Histology Block 2 Sem-1

Botulism is the only possible consideration, especially after learning that they both had canned food. Duchenne muscular dystrophy is most common in young men but very rare in older women. It would be highly unlikely that both mother and son would show symptoms of amyatrophic lateral sclerosis or myasthenia gravis or have myocardial infarct at the same time.

A triad in skeletal muscle is composed of three components, a T tubule and two terminal cisternae of the sarcoplasmic reticulum (SR) that flank it. The SR, not the T tubules, sequesters calcium ions.

Cardiac muscle cells are joined together end-to-end by a unique junctional specialization
called the intercalated disk.

Titin forms an elastic lattice that anchors thick filaments to Z disks.

Smooth muscle cells contain one centrally located nucleus.

Perimysium surrounds Fasicles.
The endomysium is a thin connective tissue layer, composed of reticular fibers and an external lamina, that invests individual muscle fibers (cells).
The EPIMYSIUM surrounds the entire muscle.

The endomysium is a thin connective tissue layer, composed of reticular fibers and an external
lamina, that invests individual muscle fibers (cells). The epimysium surrounds the entire
muscle, and the perimysium surrounds bundles (fascicles) of muscle fibers.

Smooth muscle cells do not have T tubules. Contraction may be initiated by stretching, neural impulses, the intercellular passage of small molecules via gap junctions, or the action of hormones such as oxytocin. The process of contraction is not dependent on troponin, which is absent from the thin filament of smooth muscle. Instead, calcium ions controlled by sarcolemmal vesicles known as caveolae are released into the cytosol, where they bind with calmodulin. The calcium-calmodulin complex activates myosin light chain kinase, which participates in the contraction process.

Binding of calcium ions to the TnC subunit of troponin leads to the uncovering of myosinbinding
sites on actin (thin filaments).

The T tubules of skeletal muscle cells are positioned so that they form triads with the terminal cisternae of the sarcoplasmic reticulum at the interface of the A and I bands.

C protein (clamp protein) anchors at the M-line.
Titin forms an elastic lattice that anchors thick filaments to Z disks.
Nebulin anchors to THIN filaments

The T tubules of cardiac muscle cells are wider than those of skeletal muscle cells and are lined by external lamina (a basal lamina-like material). In contrast to skeletal muscle, the T tubules are located at the Z disk, where they often form dyads. Individual cardiac muscle cells are attached to one another by intercalated disks.