Chapter_12_Muscle_Physiology

Chapter_12_Muscle_Physiology - Chapter 12 Muscle Physiology...

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Chapter 12 Muscle Physiology IT IS CRITICAL THAT YOU VIEW THE CD BEFORE COMING TO CLASS!! Be sure you know the following: Skeletal Muscle Structure The Mechanism of Force Generation in Muscle The Mechanics of Skeletal Muscle Contraction Types of Skeletal Muscle Fibers Smooth and Cardiac Muscle FUNCTIONS 1. generate motion 2. generate force 3. generate generate heat TYPES 1. skeletal 2. smooth 3. cardiac Structure and Actions Skeletal muscle attached to bone by tendons Tension on tendons by muscles cause movement of the bones. Abuse of anabolic steroids increases muscle mass without corresponding increase in tendon strength Golgi tendon organs fig. 12.31monitor tension & prevent excessive stretching Series-Elastic Component Non-contractile tendons and connective tissue absorb tension as the muscle contracts Tendons first must be pulled tight, before the muscle contraction results in shortening Tendons: Have elasticity Display Intra-Versus Extrafusal Fibers Extrafusal fibers Contractile cells of the muscle Responsible for skeletal muscle contraction Innervated by alpha motor neurons Intrafusal fibers Contractile cells of the muscle spindle Adjust sensitivity of muscle to stretch
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Innervated by gamma motor units Muscle Terminology Muscle Cell = muscle fiber Cell membrane = sarcolemma Cytoplasm = sarcoplasm ER = sarcoplasmic reticulum Muscle = group of fascicles Muscle fibers extend length of muscle from tendon to tendon Components of a Muscle Fiber Muscle fibers surrounded by connective tissue Sarcolemma = plasma membrane Multinucleated Sarcoplasm = cytoplasm Components of a Muscle Fiber Contains many myofibrils Sarcoplasmic reticulum = smooth ER Contains many mitochondria- high energy Transverse tubules = T tubules Structure of a Skeletal Muscle Fiber fig 12.2 Myofibrils Myofibrils give skeletal/cardiac muscle striated appearance Orderly arrangement of thick and thin filaments Actin thin Myosin thick Striations due to thick and thin filaments which run parallel to long axis Filaments form sarcomeres Sarcomere Structure fig 12.3 A band - dark striations, thick filaments I band - light striations, thin filaments only, no overlap H zone - thick only, no overlap Z line – link thin filaments Sarcomere Structure fig 12.5d **EXAM PICTURE**
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Structure of a Thin Filament fig 12.4 3 Proteins in thin filaments Actin Tropomyosin Troponin Actin has binding sites for myosin Actin Each G actin has a binding site for myosin Tropomyosin Overlaps binding sites on actin for myosin Troponin Regulatory protein Complex of three proteins Attaches to actin Attaches to tropomyosin Binds calcium reversibly ******Calcium binding to troponin regulates skeletal muscle contraction
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Chapter_12_Muscle_Physiology - Chapter 12 Muscle Physiology...

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