LessonNo5MuscleFall10

LessonNo5MuscleFall10 - Physiology BIO 240 Lecture No. 5...

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Click to edit Master subtitle style Physiology BIO 240 Lecture No. 5 Muscle – Molecular Overview, Electrical Potentials, Myocyte Contraction and Energy Requirements Fall 2010 Dr. Ana M Jimenez
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Types of Muscle Smooth Muscle – non-striated muscle found in viscera (organs) and blood vessels, iris of the eye, arector pilli uninucleated, under involuntary control (ANS), Cardiac Muscle – striated muscle found in heart (atria and ventricles), uninucleated, controlled by cardiac conduction system (ANS), Skeletal Muscle – striated muscle found in muscle that attaches to skeleton, multinucleated, under voluntary control (Motor Fibers).
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Thinking About Muscles Sarcomeres contract when, Ca+2 and ATP are available Ca+2 is released from SR Skeletal muscle is under voluntary control, Muscle cells and neurons are ‘excitable’ cells – can conduct ‘electricity’, Excitable cells are like batteries separation of charge across the membrane is maintained by Na-K-ATPase pump, Increased membrane permeability allows ions through.
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Muscle Cell Characteristics Responsiveness (excitability): Responds to electrical charges. Conductivity: Conduct electrical signals. Contractility : Cells shorten. Extensibility : Cells elongate. Elasticity : Cells return to their size after being stretched.
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Muscle Fiber Is a mature muscle cell, Specialized sarcolema for excitability Specialized myofibrils: Made of Myofilaments Specialized organelles for Ca++ Sarcoplasmic reticulum Triad (3 components) : One transverse tubule (t- tubule) Two endoplasmic reticulum cisternea (folds) on each side Myofibrils (myo=muscle, fibrils=fibers), Made up of Myofilaments - Thick and Thin myofilaments for contraction and Elastic myofilameants for support
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Thick Myofilaments Made of the protein Myosin , Shaped like a golf club with a long shaft called the tail and a double globular ‘head’ , Heads face outward to each side - can chemically bind to actin, Tails line together, ~15 nm diameter
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Thin Myofilaments ~ 7 nm diameter intertwined strands of: Globular (G) actin - Enzyme that binds myosin, Tropomyosin : long protein, fits in the groves of the thin filament and blocks ‘open’ sites on G actin, Troponin : binds to tropomyosin and binds Ca++.
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Figure 11.3d
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Sarcomere Functional contractile unit of a muscle fiber (from Z-disk to Z-disk), When myosin (thick filament) binds actin (thin filament) they from cross-bridges , Myofibrils ‘slide’ past each other to bring the z-disks come closer together, Sarcomeres shorten along the myofiber, When ‘relaxed’ they elongate.
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Figure 11.4
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Striations A bands : anisotropic ( A ), d a rk bands, consists of thick and thin filaments overlaping each other. H band
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This note was uploaded on 10/04/2011 for the course BIOLOGY 240 taught by Professor Anamjimenez during the Fall '10 term at Barry Univesity.

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LessonNo5MuscleFall10 - Physiology BIO 240 Lecture No. 5...

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