Muscles

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Anonymous
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70275
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Muscles
Updated:
2011-03-02 19:12:43
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Muscles by Melanie
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Anatomy & Physiology Lecture
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  1. —Types of Muscular Tissue
    • –Skeletal
    • --Skeletal muscle tissue is striated:
    • --voluntary
    • –Cardiac
    • Smooth
  2. Connective Tissue Components
    • Fascia: –Dense sheet or broad band of irregular connective tissue that surrounds muscles
    • Epimysium: –The outermost layer –Separates 10-100 muscle fibers into bundles called fascicles
    • Perimysium: –Surrounds numerous bundles of fascicles
    • Endomysium: Separates individual muscle fibers from one another
    • Tendon: Cord that attach a muscle to a bone
    • Aponeurosis: Broad, flattened tendon
  3. Anatomy of Muscle Tissue
  4. Skeletal Muscle Tissue
    • Myofibrils: thread like structures with contractile function
    • Sarcoplasmic Reticulum (SR): membranous sacs encircling myofibril. Stores Ca++... release of Ca++ triggers muscle contraction
    • Filaments: function in contractile process... 2 thin filaments for each thick filament
    • Sarcomeres: compartments of arranged filaments, basic functional unit of a myofibril
  5. Skeletal Muscle Tissue Organization
    • Z discs: Separate one sarcomere from the next
    • Thick and thin filaments overlap one another
    • —A band: Darker middle part of the sarcomere
    • Thick and thin filaments overlap
    • —I band: Lighter, contains thin filaments but no thick filaments
    • Z discs: passes through the center of each I band
    • —H zone: Center of each A band which contains thick but no thin filaments
    • —M line: Supporting proteins that hold the thick filaments together in the H zone
  6. Skeletal Muscle Tissue Organization
  7. Skeletal Muscle Tissue Organization
  8. Contraction and Relaxation of skeletal muscle - Nerve impulses elicit a muscle action potential in the following way.
    • 1) Release of acetylcholine: –Nerve impulse
    • arriving at the synaptic end bulbs causes many synaptic vesicles to release ACh into the synaptic cleft
    • 2) Activation of ACh receptors: Binding of ACh to the receptor on the motor end plate opens an ion channel. –Allows flow of Na+
    • to the inside of the muscle cell
    • 3) Production of muscle action potential: –The inflow of Na+ makes the inside of the muscle fiber more positively charged triggering a muscle action potential. –The muscle action
    • potential then propagates to the SR to release its stored Ca++
    • 4) Termination of ACh activity: –Ach effects last only briefly because it is rapidly broken down by acetylcholinesterase (AChE)
  9. The Contraction Cycle
    • SR releases Ca++ into the muscle cell
    • Ca++ binds to actin opening the myosin binding sites
    • ATP hydrolysis reorients and energizes the myosin head
    • Cross bridges form when the myosin head attaches to the actin
    • Power Stroke - cross bridges rotate sliding the filament
    • Detachment of myosin from actin - ATP binds to the myosin head thus detaching it from the actin
  10. Visual of Muscle Contraction
  11. What is a motor unit
    • Consists of a motor neuron and the muscle fibers it stimulates.
    • A motor neuron makes contact with about 150 muscle fibers
    • –Muscles that control voice production have 2 - 3 muscle fibers/mu
    • –Muscles controlling eye movements have 10 - 20 muscle fibers/mu
    • –Muscles in the arm and the leg have 2000 - 3000 muscle fibers/mu
  12. Twitch Contraction
    • Latent Period: brief delay between stimulus and contraction
    • Contraction Period: Ca++ binds to troponin - cross bridges form
    • Relaxation Period: Ca++ transported to SR - tropomyosin covers myosin binding sites - myosin heads detach from actin
    • Refractory period: when a muscle fiber contracts it temporarily cannot respond to another action potential.
  13. Control of Muscle Tension

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