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Lecture

Muscular System Notes.docx

3 Pages
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Department
Communication
Course Code
COMM 1020
Professor
Dibenedetto

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Muscular System • Muscle Cell – muscle fiber (repair by means of satellite cells) – multinucleated, a  lot of mitochondria, glycosomes, myoglobins(O2 storage) • Cell membrane – sarcolemma  o Fascial organization – endomysium, perimysium, epimysium;  • Cytoplasm – sarcoplasm  • Modified ER – sarcoplasmic reticulum Muscle fiber action potential (nerve vs. muscle) • Slower than nerve but involving entire cell’s membrane Skeletal muscle fiber characteristics: • Contractile proteins – myosin(thick filaments) and actin (thin filaments,  troponin, tropomyosin) o TnC (Calcium), TnI(inhibitor), TnT (tropmyosin bound) • Regulatory proteins – troponin (complex) and tropomyosin (regulator) • Structural proteins – titin (big), myomesin (spring), nebulin (stiffen actin), and  dystrophin (cytoskeleton protein biggie) • Triad – T­Tubule between SR, CA storage • H zone = thick, A zone = thick and thin, I band = thin, H zone disappears when  contracted •  Tendon, sliding filament theory/ process  o 1) Myosin head tightly bound to actin o 2) ATP binds to myosin head, releases from actin o 3) ATP hydrolyzed into ADP and Pi, Myosin head binds weakly to actin o 4) Pi leaves initiating power stroke, myosin head pulls actin past it o 5) ADP leaves and myosin head bound tightly to acting again •  Excitation –contraction couplin  1. Nerve impulse reaches axon terminal and synaptic vesicles release Ach 2. Ach diffuses to receptors on the sarcolemma and Na+ channels open and  Na+ rush into cell 3. Action potentials spread over sarcolemma into T­tubules 4. Voltage gated Calcium channels open to interstitum, DHP (dihydropyridine  controls release of Ca from SR) receptors activated 5. SR releases Ca into sarcoplasm 6. Ca binds to troponin and causes complex to reveal myosin binding sites •  Calcium regulation  o From T tubules DHP proteins release from the SR on each side of the  tubules, o Huge Calcium storage fa
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