Title: Muscle tissue - AMBOSS
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Muscle tissue
Summary
Muscle cells (myocytes)
Myofilaments
Myofilament contraction
Energy provision for muscle contraction
Skeletal muscle
Smooth muscle
Cardiac muscle
Clinical significance
References

Content: which contains membrane invaginations
Characteristics
Transverse tubules ( T-tubules)
Transverse tubular invaginations of the sarcolemma of striated muscle cells
Transmit the action potential (AP) to the sarcoplasmic reticulum; ( close proximity of T-tubules to adjacent terminal cisternae allows for direct transmission of APs to the sarcoplasmic reticulum → quick release of Ca 2+ for muscle contraction)
Responsible for synchronization of AP transmission and muscle contraction
Caveolae
Invaginations in the sarcolemma of smooth muscle cells, located close to the sarcoplasmic reticulum
Contain various receptors and ion channels involved in signal transduction
Sarcoplasm
Definition: muscle cell cytoplasm
Contents
Myofibrils (consisting of myofilaments)
Glycosomes (granules of stored glycogen)
Myoglobin
Ca 2+ (to initiate contraction by binding troponin)
Sarcoplasmic reticulum ( SR)
Definition: muscle cell end oplasmic reticulum, which forms a network of L-tubules
Characteristics
Terminal cisternae: the ends of L-tubules which encircle myofibrils and lie adjacent to T-tubules
Triad ( skeletal muscle ): one T-tubule and two terminal cisternae
Diad ( cardiac muscle ): one T-tubule and one terminal cisterna
Stores Ca 2+
Myofilaments
See section below. Comparison of muscle cell types [1]
Structural differences between muscle cell types
Muscle fiber
Location
Cell morphology
Sarcolemma
Striated muscle fibers
Skeletal muscle
Large elongated cells with multiple nuclei located at the periphery
Triad: one T-tubule and two terminal cisternae
Cardiac muscle
Branched cells with a central nucleus
Diad: one T-tubule and one terminal cisterna
Nonstriated muscle fibers
Smooth muscle
Spindle-shaped cells with a central nucleus
Caveolae
Myofilaments
Myofilaments are protein fibers consisting of thick ( myosin) and thin ( actin) filaments and are responsible for the contractile properties of muscle cells. Actin myofilaments ( thin filaments) [1]
Structure
Actin myofilaments are thin filaments composed of actin molecules, regulatory proteins, and nebulin. Regulatory proteins prevent permanent interaction between myosin and actin.