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The Muscular System

Overview. Functions of Skeletal MuscleThe Anatomy of Skeletal MuscleGross anatomyMicroanatomyThe Control of Muscle Fiber ContractionThe neuromuscular junctionThe contraction cycleMuscle MechanicsThe frequency of muscle fiber stimulationThe number of muscle fibers involvedIsotonic and isome

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The Muscular System

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    1. The Muscular System Chapter 7 Pgs 177-195

    2. Overview Functions of Skeletal Muscle The Anatomy of Skeletal Muscle Gross anatomy Microanatomy The Control of Muscle Fiber Contraction The neuromuscular junction The contraction cycle Muscle Mechanics The frequency of muscle fiber stimulation The number of muscle fibers involved Isotonic and isometric contractions Muscle elongation The Energetics of Muscular Activity ATP and CP reserves ATP generation Muscle fatigue The recovery period Muscle Performance Types of skeletal muscle fibers Physical conditioning Cardiac Muscle Tissue Smooth Muscle Tissue

    3. Functions of Skeletal Muscle Produce movement Maintain posture and body position Support soft tissues Guard entrances and exits Maintain body temperature

    4. The Anatomy of Skeletal Muscles Macroanatomy and microanatomy We will use the CD for this!

    5. Neuromuscular Junction We will use the CD for this as well!

    6. The Contraction Cycle Guess what we will be using again?!

    7. Muscle Mechanics Tension An active force generated when muscle cells contract and pull on surrounding collagen fibers Before movement, tension must overcome object’s resistance Dependant upon object’s weight, shape, friction Compression Push applied to object; forces object away from source Muscles can shorten and generate tension but do not lengthen and generate compression!

    8. Muscle Mechanics All or none principle Amt of tension produced by 1 muscle fiber depends only on # cross-bridges activated Always produce same amt of tension Amount of tension produced by whole muscle determined by: Frequency of stimulation Number of muscle fibers activated

    9. The Frequency of Muscle Fiber Stimulation

    10. Freq: Summation and Tetanus (Incomplete and Complete)

    11. The Number of Muscle Fibers Involved Total force exerted depends on # muscle fibers recruited Motor unit All of the muscle fibers controlled by one motor neuron Size indicates how fine the control of movement is Eye vs. legs Recruitment Steady and smooth increase in muscular tension Produced by increasing # of active motor units Muscle tone

    13. Isotonic Contraction

    14. Isometric Contraction

    15. Example: Squats

    16. Muscle Elongation No active mechanism for fiber elongation Rather, it is passive Returns 1 of 3 ways or combo: Elastic forces Opposing muscle movements Gravity

    17. The Energetics of Muscular Activity We will use the wonderful CD for this!

    18. Muscle Fatigue: How long can you do this?

    19. Muscle Performance Considered in terms of: Power Maximum amount of tension produced by a particular muscle or group Endurance The amount of time for the individual to perform a particular activity 2 deciding factors: Type of muscle fibers w/in the muscle Physical condition or training

    20. Types of Skeletal Muscle Fibers Fast Twitch Fibers Contract in 0.01 seconds Large in diameter Lots of myofibrils Glycogen reserves? # of Mitochondria? # of capillaries? Myoglobin? Fatigue quickly or slowly? Slow Twitch Fibers 3Xs the time to contract Small diameter Glycogen reserves? # of mitochondria # of capillaries Myoglobin? Fatigue quickly or slowly

    21. Physical Conditioning Anaerobic activities Hypertrophy Enlargement of muscle fibers Aerobic activities

    22. Cardiac Muscle Tissue: Differences from Skeletal Structural Differences Intercalated disks Functional Differences Pacemaker cells Contractions last 10Xs long as skeletal Cell membrane differences Release of calcium increases permeability to extracellular calcium ions Rely on only aerobic metabolism

    24. Smooth Muscle Tissue: Differences from Other Muscle Structural No myofibrils, sarcomeres, striations Thin filaments anchored w/in cytoplasm to sarcolemma Adjacent smooth muscle cells bound together at anchoring sites Transmits contractile forces throughout tissue

    26. Smooth Muscle Functional Differences Calcium ions trigger contractions differently Smooth muscle cells contract over greater range of lengths b/c actin and myosin not rigidly organized Many cells not innervated by motor neurons Pacesetter cells Environmental stimulation Hormonal stimulation

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