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Three types of muscle tissue?
- 1) skeletal (striated, voluntary)
- 2) visceral or smooth (nonstriated, involuntary)
- 3) cardiac (striated, involuntary)
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Basic functions of muscle?
- 1) movement (primary)
- 2) maintain posture
- 3) heat generation
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General characteristics of muscle?
- 1) excitability
- 2) contractility
- 3) extensibility
- 4) elasticity
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Microscopic struture/anatomy (skeletal muscle)?
- 1) sarcolemma (plasma membrane)
- 2) sarcoplasm (cytoplasm)
- 3) specialized organelles
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Sarcolemma (plasma membrane)
surrounds sarcoplasm w/ openings scattered across surface that lead into a network of narrow tubules calles transverse tubules (T tubules)
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Myofibrils
- 1) encircled by T-tubules
- 2) 1-2um diameter - as long as the entire muscle
- 3) hudreds to thousands are contained in each muscle fiber
- 4) bundles of thick & thin myofilaments
- 5) responsible for muscle fiber contraction
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Myofilaments
protein filament that consist primarily of the proteins actin & myosin
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Actin
- 1) protein found in protein filaments contained in myofilaments
- 2) actin molecules are found in the thin filaments
- 3) attracted to myosin
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Myosin
- 1) protein found in protein filaments contained in myofilaments
- 2) myosin molecules are found in the thick filaments
- 3) attacted to actin
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Mitochondrea & Granules of Glycogen
- 1) scattered among the myofibrils, a source of glucose
- 2) breakdown of glucose & the activity of the mitochondria provide the ATP needed to power muscle contraction
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Sarcoplasmic Reticulum (SR)
- 1) forms tubular network around each myofibril
- 2) specialized for of endoplasmic riticulum
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T-tubules (transverse tubules)
- 1) create a network of narrow tubules that form passageways through the muscle fiber
- 2) filled w/ extracellular fluid
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Terminal Cisternae
- 1) expanded chamber of SR containing high concentration of calsium ions
- 2) wherever T-tubules encircles a miyofibril it is tightly bound to the membranes of the SR
- 3) located on either side of where T-tubules encircles a microfibril
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Triad
it is formed where SR encircles a myofibril & a T-tubule lies sandwiched between a pair of terinal cisternae
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Muscle contraction begins...
when stored calsium ions are released from the terminal cisternae into the sarcoplasm.
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Sarcomeres
- 1) what myofilament (thick & thin fillaments) are organized into
- 2) they are repeating functioning units
- 3) each myofibril consists of aprox 10k arranged end to end
- 4) smallest functional unit of the muscle fiber
- 5) interactions between thick & thin filaments here are responsible for muscle contraction
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Rigor Mortis
- 1) aprx 6hrs after death
- 2) skeletal muscles have depleted all glucose & ATP molecules
- 3) waste products accumulate (metabolic acids)
- 4) ATP gone -> sarcoplasmic riticulum cannot remove calcium ions from the sarcoplasm
- 5) myosin fibers can't separate from actin fibers, & rigor mortis, sustained contraction, sets in
- 6) 12-24hrs later, lysosomal enzymes from muscle cells breakdown contracted myofilaments, & muscles relax
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