A&P Chapter 10: Muscle Tissue

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evander4
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A&P Chapter 10: Muscle Tissue
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2013-05-02 08:02:55
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Muscle tissue
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Muscle tissue
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  1. What are the 6 functions of muscle tissue?
    • 1. Produce skeletal movement (contract)
    • 2. Maintain posture and body position
    • 3. Support soft tissues
    • 4. Guard entrances and exits (sphincters)
    • 5. Maintain body temperature
    • 6. Store nutrient reserves (glycogen)
  2. What are the 3 levels of organization in muscle tissue?
    • 1. Epimysium: exterior collagen layer, isolates muscles from surrounding tissues
    • 2. Perimysium: Surrounds muscle fiber bundles(fascicles), contains blood vessel and nerve supply to the fascicles
    • 3. Endomysium: Surrounds individual muscle fibers, contains capillaries and nerve endings, contains myosatellite cells that repair damage
  3. Compare/contrast the characteristics of skeletal, cardiac and smooth muscle
    • 1. Skeletal: Striated, multinucleate, voluntary
    • 2. Cardiac: Striated, intercalated discs, branched, involuntary
    • 3. Smooth: Non striated, involuntary

    ALL: Help to maintain body temperature
  4. What are the components found in a muscle fiber?
    • 1. Sarcolemma: cell membrane of muscle fiber, change in transmembrane potential begins contractions
    • 2. Sarcoplasm: cytoplasm of muscle fiber
    • 3. T Tubules: transmit action potentials through cell, allows entire muscle fiber to contract simultaneously
    • 4. Myofibrils: made up of bundles of myofilaments (actin/myosin) that are responsible for contractions
    • 5. Sarcoplasmic Reticulum (SR): stores calcium, helps transmit action potentials, forms chambers attached to T tubules
    • 6. Sarcomeres: The contractile unit of the muscle fiber, form striated appearance with overlap of thick and thing filaments
  5. Excitation-Contraction coupling involves excitation of the muscle fiber and contraction. What are the 6 steps of excitation?
    • 1. At neuromuscular junction, the cytoplasm of neuron contains ACh
    • 2. AP arrives in the syn+aptic terminal
    • 3. AP causes the release of ACh into the synaptic cleft
    • 4. ACh binds to receptors on the sarcolemma of the muscle fiber depolarizing the membrane to threshold
    • 5. Sudden rush of Na+ into the muscle fiber results in an AP
    • 6. AP travels down T tubules into the SR causing the release of Ca2+ into the sarcomere
  6. Excitation-Contraction coupling involves excitation of the muscle fiber and contraction. What are the 5 steps of contraction?
    • 1. Ca2+ binds to troponin causing it to change shape and roll away tropomyosin, exposing the myosin binding sites on actin
    • 2. Myosin heads get energy by breaking ATP into ADP+P, energized myosin heads bind to actin forming a cross bridge
    • 3. Energy stored in myosin is released as myosin head pivots towards the M line, called power stroke
    • 4. When another ATP binds to the myosin head, it releases from actin and the attachment site is exposed so it can bind with another myosin head
    • 5. The myosin is reactivated when it breaks ATP into ADP+P again, energy released is used to re-cock the myosin head to be ready for another cross bridge formation and power stroke
  7. What are the different types of contractions produced by a muscle?
    • 1. Treppe: stair-step increase in twitch tension, repeated stimulations after relaxation phase, causes series of contractions with increasing tension
    • 2. Wave summation: increasing tension, summation of twitches, repeated stimulation before the end of relaxation phase, causes increasing tension (summation of twitches)
    • 3. Incomplete tetanus: twitches reach maximum tension, continuous, rapid stimulation prevents muscles from relaxing, twitches reach maximum level of tension
    • 4. Complete tetanus: if stimulation frequency is high enough, muscle never begins to relax, remains in continuous contraction, happens when load exceeds capability
  8. What is a motor unit?
    • A motor unit is a skeletal muscle and the neuron that controls it:
    • 1. Contains hundreds of muscle fibers
    • 2. Contract at the same time
    • 3. Controlled by a single motor neuron
  9. What is motor recruitment?
    • 1. multiple motor unit summation
    • 2. in a whole group of muscles, smooth motion and increasing tension are produced by slowly increasing the size or number of motor units stimulated
    • 3. Maximum tension: when all motor units reach tetanus, only sustained for a short time
  10. What happens as the muscle relaxes?
    • 1. Ca2+ concentrations fall, Ca2+ detaches from troponin, active sites on actin are re-covered by tropomyosin
    • 2. Pull of elastic tendons and ligaments return sarcomeres to resting length
    • 3. Opposing muscle contraction reverses the direction of original motion (opposing skeletal muscle pairs)
    • 4. Gravity can return muscle to its original state
  11. How do muscles create the energy they need to work?
    • 1. ATP: muscles store enough ATP to start a contraction, the rest comes from glycolysis and aerobic respiration in the mitochondria
    • 2. CP: Creatine phosphate stores excess ATP in resting muscles
    • 3. Stored ATP lasts for 2 sec to initiate contraction --> muscle makes ATP from CP --> anaerobic glycolysis breaks down glucose for ATP --> aerobic metabolism breaks down fatty acids for ATP
  12. What are the 2 different types of muscle fibers?
    • 1. Slow: resistant to fatigue, thin, red, many mitochondria
    • 2. Fast: fatigue quickly, large, white, few mitochondria
  13. What structures to cardiac muscle cells have that enable them to communicate with each other?
    • 1. Intercalated discs: Gap junctions at branches of cardiac muscle allow muscle cells to communicate quickly
    • 2. Discs link heart cells mechanically, chemically, and electrically allowing heart to function as a single, fused mass of cells

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