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Published byClaribel Ross Modified over 9 years ago
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Muscle Tissue Specialized for contraction Elongated cells
3 types of muscle: skeletal, cardiac, smooth
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Organization of Skeletal Muscle
Sarcolemma = muscle cell membranes Sarcoplasm = cytoplasm Sarcoplasmic reticulum = endoplasmic reticulum Muscle cell = muscle fiber (not like a CT fiber)
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Skeletal Muscle (voluntary, striated)
longitudinal section Long, cylindrical shaped cells Nuclei are multiple and peripherally located Striated (striped) appearance due to banding pattern: A band, I band, Z line, H band.
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Sarcomere – the basic contractile unit of skeletal muscle; extends from Z-line to Z-line
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Myofilaments = the contractile elements of skeletal muscle; = myosin (thick filaments) and actin (thin filaments) actin myosin
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Motor end plate – the region of sarcolemma contacted by the axon terminals of a motor neuron.
higher power
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Neuromuscular Junction – the site of neurotransmitter (acetylcholine) release
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Skeletal Muscle (cross-section)
low power higher power
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Cardiac Muscle - Striated
Single, large, oval, centrally located nucleus Branched cells Intercalated disks = specialized end-to-end junctions
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Cardiac Muscle (longitudinal sections)
intercalated disk striated, branching cells
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Intercalated Disks - anchor myofibrils and permit fast transmission of contractions; consist of 3 components:
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Lots of Mitochondria (tiny black dots) in Cardiac Muscle
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Purkinje Fibers - large, modified cardiac muscle cells; transmit electrical impulses to cardiac muscle.
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Smooth Muscle (involuntary)
- Forms the walls of hollow organs and bodily tubes - Important in sphincters, peristalsis, blood pressure regulation. – Activated by autonomic nervous system and hormones. longitudinal section
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Smooth Muscle Cells are fusiform in shape – round at center and tapered at ends. A single nucleus, centrally located. When contracted, nuclei may have a corkscrew appearance. No striations – actin & myosin present but not regularly arranged in a repeated pattern. Cells connected to each other by gap junctions that allow conduction of impulses and contraction from one cell to another.
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Smooth Muscle (top: cross-section; bottom: longitudinal section)
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Summary of the 3 Muscle Types
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