Muscle physiolgy - Muscle Physiology Objectives: To...

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1 Muscle Physiology Objectives: • To understand the organization of a skeletal muscle fiber and sarcomere and the molecular basis of muscle contraction • To understand excitation-contraction coupling • To learn organization and function of different muscle types
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2 3 types of muscle Skeletal muscle : attached to bones, control body movement striated (alternating light and dark bands Cardiac muscle : found only in the heart striated Smooth muscle: found in internal organs such as stomach, urinary bladder, and blood vessels not striated
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3 Skeletal Muscle • Often described as voluntary muscles • Contract in response to a signal from a somatic motor neuron – cannot contract on their own, contraction not influenced by hormones • Bulk of muscle in body and 40% of body weight • Attached to bones by tendons (collagen) • Origin of a muscle is the end attached closest to the trunk • Insertion of the muscle is the more distal (distant) attachment
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4 Antagonistic Muscle Groups Most joints have antagonistic muscle groups : flexor muscles : bones are brought close together extensor muscles: bones move away from each other
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6 Muscle Fibers Skeletal muscle is a collection of muscle fibers Each muscle fiber is made up of several hundred nuclei on the surface of the fiber Muscle fibers are the largest cells in the body - many fused cells Groups of muscle cells that function together and share a common motor neuron are called a motor unit small muscles have a few motor units large muscles may have several thousand motor units Fine touch 1:1 nerve to fiber Finger tips Big muscles 1: 2000 nerve to fiber Leg muscles
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7 Sarcomere: One Repeat Z disks : zig-zag proteins, attachment sites for thin filaments A band : darkest b/c thick and thin filament overlap at outer edge H zone : thick filaments only I bands : lightest color bands, only thin filaments crossbridges : myosin heads loosely bind to actin filaments M line : attachment site for thick filaments
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8 Myofibrils are Composed of Several Types of Proteins Contractile proteins: Myosin : thick filaments different types of muscle contain different types of myosin, related to speed of contraction two heavy chains intertwine to form a coiled tail and a pair of heads composed of 250 myosin molecules make up a thick filament Actin : thin filaments Multiple globular proteins (G-actin) polymerize to form long chains (filaments) Two filaments twist to create one thin filament Regulatory proteins: tropomyosin, troponin help regulate contraction Accessory proteins: titin, nebulin - help maintain proper alignment of overlapping thin and thick filaments
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The sarcomere is composed of: thick filaments called myosin , anchored in place by titin fibers , and thin filaments called actin , anchored to Z-lines . Myofibrils: Contractile Proteins
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This note was uploaded on 01/12/2012 for the course BMED 3110 taught by Professor Staff during the Spring '08 term at Georgia Institute of Technology.

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Muscle physiolgy - Muscle Physiology Objectives: To...

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