Three types of muscle Skeletal – attached to bone
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Transcript of Three types of muscle Skeletal – attached to bone
• Skeletal – attached to bone• Cardiac – found in the heart• Smooth – lines hollow organs
Three types of muscle
• Produce skeletal movement• Maintain posture and body position• Support soft tissues• Guard entrances and exits• Maintain body temperature
Skeletal muscle functions
• Epimysium- collagen fibers that surrounds muscle– covers individual muscle fibers
• Perimysium- a connective tissue partition that separate adjacent fasciculi in a skeletal muscle– Fasciculus- a small bundle; usually refers to a collection of
muscle fibers or nerve axons– Epimysium and perimysium contain blood vessels and
nerves
• Endomysium- surrounds individual fibers; satellite (stem) cells between
• Tendons, or aponeuroses, attach muscle to bone or muscle
Organization of connective tissues
Figure 10.1
Figure 10.1 The Organization of Skeletal Muscles
• Sarcolemma- plasma membrane; surrounds sarcoplasm; invaginates to form Transverse (T) tubules
– T tubules- narrow tubes that are continuous with the sarcolemma and extend into the sarcoplasm at right angles to the cell surface
– Sarcoplasm- muscle cell cytoplasm
Skeletal muscle fibers
Sarcoplasmic reticulum (SR)- modified ER; located near T tubules; surround myofibrils
- SR store and release Ca2+
- Calsequestrin within binds Ca2+
- Myofibril- Organized collections of myofilaments in skeletal and cardiac muscle cells
- surrounded by mitochondria and glycogen- thick and thin filaments
- organized regularly
T-tubules and myofibrils aid in contractionSarcomeres – regular arrangement of myofibrils
Skeletal muscle fibers cont.
Figure 10.3
Figure 10.3 The Structure of a Skeletal Muscle Fiber
• Sarcomers- repeating functional units of myofibrils (n=10,000/fibril)– Has alternating A (dark) and I bands
• A Band- The thick filaments are located at at the center of the sarcomere (i.e width of thick filament)
– center is the M line– H zone- lighter region on either side of the M line
» has thick, but no thin, filaments
Sarcomeres
- I Band- only thin filaments and extends from A band of one sarcomere to A band of next sarcomere
- centered by Z line (striation) - separates sarcomeres- its actinins (protein) join filaments of sarcomeres; titin (protein) attaches thick filaments to Z lines
Thin filaments: F actin- double twisted strand of G actin (protein); held together by nebulin - Tropomyosin covers active sites - Troponin- binds one of its three globular subunits to tropomyosin, creating a troponin-Tropomyosin complex - second subunit binds to one G actin (holds complex together) - third subunit has a receptor that binds one Ca2+ ion
Sarcomeres cont.
Sarcomeres cont.
Thick filaments- A cytoskeletal filament in a skeletal or cardiac muscle
- composed of myosin (protein) with a core of titin
- myosin molecules have elongate tail, globular head - heads form cross-bridges during contraction- interactions between G-actin and myosin
prevented by tropomyosin during rest
Figure 10.4 Sarcomere Structure, Part I
Figure 10.4
Figure 10.5 Sarcomere Structure, Part II
Figure 10.5