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Ch 9 Muscular System Naming of Muscles • Preview the outline: What do you notice about the names of the muscles? Muscle nomenclature • • • • Directional e.g. Lateralis, medialis Specific regions e.g. abdominus, brachialis, oculoOrigin e.g. biceps, triceps, quadriceps Shape e.g. deltoid, orbicularis, serratus, trapezius • Other features e.g. brevis, longus, magnus • Actions e.g. abductor, adductor, flexor, extensor • Specific references e.g. buccinator (trumpeter), sartorius (like a tailor) Musculoskeletal System • Movement occurs from the • interaction between muscles & bones is made up of: muscles bones joints What would you NOT be able to do if you lacked muscles? A) Muscle Functions 1. Produce body movements 2. Stabilize body positions standing, sitting maintaining posture 3. Regulate volume contents in organs e.g. sphincter muscles prevent outflow of stomach 4. Move substances (internally) Cardiac muscle-moves blood through blood vessels Smooth muscle-moves food & urine/feces, push gametes, regulate blood flow through blood vessels Skeletal muscle-helps return blood back to heart 5. Produce heat B) Types of Muscles 1. Skeletal muscle- attach to bones & moves part of the skeleton striated, long cells multinucleated voluntary 2. Cardiac muscle- found only in heart striated, branched cells intercalated disks involuntary 3. Smooth muscle- found in walls of hollow organs (stomach, intestines), blood vessel walls, airways not striated tapered ends involuntary Attachments and Actions • Movement usually produced by a group of muscles Prime mover (agonist) – muscle responsible for most of the movement Synergists – muscles that help the prime mover by stabilizing joints Antagonist – muscle that produces movement opposite to prime mover 22-12 Relaxes when prime mover contracts C) Skeletal Muscle C) Skeletal Muscle • is composed of muscle fibers, connective tissue, nerves & blood vessels • Skeletal muscles are highly vascularized. to provide O2 & nutrients to muscle tissue for contraction & to get rid of waste • Skeletal muscles are also highly innervated. to signal muscles to contract D) Overall Organization of a Skeletal Muscle Figure 8.1 1. Epimysium (connective tissue) surrounds entire skeletal muscle each muscle is composed of 10-100 fascicles 2. Perimysium surrounds each fascicle Each fasicle is a bundle of muscle fibers (muscle cells) 3. Endomysium surrounds each muscle fiber (muscle cell) Each muscle fiber is composed of 100s-1000s of myofibrils A “Typical” Eukaryotic Animal Cell Tendon: an extension of epi, peri & endomysium beyond the muscle that attaches the muscle to the bone 4. Each myofibril is composed of actin & myosin protein filaments. E) Anatomy of a Skeletal Muscle Cell 1. muscle fiber = is an elongated muscle cell 2. sarcolemma = the plasma membrane of each muscle fiber 3. transverse or T- tubules = tunnels that starts at the sarcolemma & branch to the center of each muscle fiber conduct impulses throughout the muscle fiber 4. Muscles cells are multi-nucleated 5. Muscles cells have many mitochondriato produce ATP (energy) via cellular respiration for muscle contraction 6. sarcoplasmic reticulum is a network of fluid filled membrane tubules; stores Ca ions 7. sarcoplasm contains myoglobin, a red pigmented protein that carries oxygen 8. myofibrils are made of protein filaments: thick filaments = myosin thin filaments = actin 9. A sarcomere is a section of a myofibril that is the basic unit of contraction Figure 8.2a Structure of a Sarcomere 1. Filaments overlap in repeating patterns 2. Sarcomeres are separated by Z-discs 3. A-band = region of thick filaments; appears darker 4. H-zone = center of A-Band; thick filaments ONLY Structure of a Sarcomere 1. Filaments overlap in repeating patterns 2. Sarcomeres are separated by Z-discs 3. A-band = region of thick filaments; appears darker 4. H-zone = center of A-Band; thick filaments ONLY 5. I-band = region of thin filaments ONLY 6. Striations due to the alternating dark & light bands 1 2 3 1 2 3 Figure 8.2c Myosin (thick filament) Figure 8.3a pain has started means a heart attack is unlikely. Actin (thin filament) Thin filaments are made of: a) actin b) tropomyosin—blocks myosin-binding site & prevents contraction (= relaxed muscle) c) troponin—holds the tropomyosin strands in place Figure 8.4