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Lec14 Muscular System

Lec14 Muscular System - Chapter 12 Muscular System Review 3...

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Chapter 12 Muscular System
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Review: 3 types of muscle tissue Smooth – involuntary muscle found in hollow organs and vessels Smooth, Cardiac, Skeletal
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Cardiac – involuntary muscle found in the heart
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Skeletal voluntary muscle that is attached to the skeleton
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What are the functions of skeletal muscles? 1. Support the body by allowing us to stay upright 2. Allow for movement by attaching to the skeleton 3. Help maintain a constant body temperature 4. Assist in movement in the cardiovascular and lymphatic vessels 5. Protect internal organs and stabilize joints
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How are skeletal muscles arranged? Attachments: Tendon – connective tissue that connects muscle to bone Origin – attachment of a muscle on a stationary bone Insertion – attachment of a muscle on a bone that moves Action: Antagonistic – muscles that work in opposite pairs Synergistic – muscles working in groups for a common action
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Skeletal Muscles Work in “Antagonistic Pairs” Muscles can only actively contract Muscles can only actively contract Must be lengthened by another muscle Must be lengthened by another muscle Note origin and insertions triceps and biceps Note origin and insertions triceps and biceps
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Examples of how skeletal muscles are named Size – the gluteus maximus is the largest buttock muscle Shape – the deltoid is triangular (Greek letter delta is Δ) Location – the frontalis overlies the frontal bone Direction of muscle fiber – the rectus abdominus (rectus means straight) Attachment – the brachioradialis is attached to the brachium and radium Number of attachments – the biceps brachii has two attachments Action – the extensor digitorum extends the digits
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Muscles of the human body
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Muscle fibers/cells Terminology for cell structure The plasma membrane is called the sarcolemma The cytoplasm is called the sarcoplasm The SER of a muscle cell is called the sarcoplasmic reticulum and stores calcium
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Skeletal muscle fibers are long, multi-nucleated cells (50 - 200 microns diameter) Many mitochondria Muscle fibers are arranged in bundles called fascicles Myofibrils (2-3 microns in diameter) are a bundle of myofilaments that run the length of a fiber Myofilaments are proteins (actin and myosin) that are arranged in repeating units Muscles, Fibers and Myofibrils
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Myofibrils and Sarcomeres A myofibril consists of many 2-3 micron long sarcomeres laid end to end Sarcomeres are the repeating units of actin and myosin found along a myofibril In the light microscope, sarcomeres show striations A-band, I band, Z-line, and M-line, H-zone
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The sarcomere Made of two protein myofilaments Myosin : are the thick filaments shaped like a golf club Actin : are the thin filaments These filaments slide over one another during muscle contraction
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“Sliding Filaments” Sarcomeres shorten by sliding of thin filaments Sarcomeres shorten by sliding of thin filaments past thick filaments:
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