Muscle Types and Mechanics Overview
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Questions and Answers

What is required to re-energize the myosin head during the crossbridge cycling?

  • Tropomyosin
  • ADP
  • ATP (correct)
  • Calcium

    • The length of myofilaments changes during muscle contraction.

    False

    What disappears during muscle contraction, the H-zone or the A band?

    H-zone

    During excitation-contraction coupling, skeletal muscle fibers must have a direct __________ stimulus to contract.

    <p>neural</p> Signup and view all the answers

    Match the components involved in muscle contraction with their roles:

    <p>Troponin = Binds calcium and exposes binding sites Tropomyosin = Blocks myosin-binding sites on actin Calcium = Triggers muscle contraction Somatic motor neurons = Provide neural stimulus to muscle fibers</p> Signup and view all the answers

    What is the immediate energy source derived from the breakdown of creatine phosphate?

    <p>ATP</p> Signup and view all the answers

    Creatine phosphokinase (CPK) is found only in the brain.

    <p>False</p> Signup and view all the answers

    What is the primary energy source used during the first 5-10 minutes of exercise?

    <p>Glycogen</p> Signup and view all the answers

    The breakdown of glucose during glycolysis produces __________ and ATP.

    <p>pyruvate</p> Signup and view all the answers

    What is the region called where actin and myosin filaments overlap?

    <p>A-band</p> Signup and view all the answers

    The I-band contains both actin and myosin filaments.

    <p>False</p> Signup and view all the answers

    Match the following energy sources with their associated processes:

    <p>Creatine phosphate = Rapid energy supply for short bursts of exercise Glycogen = Primary energy source in the early stages of exercise Fatty acids = Sustained energy after glycogen stores are depleted Blood glucose = Source of energy after initial glycogen breakdown</p> Signup and view all the answers

    What attaches from the Z-line to the M-line in a sarcomere?

    <p>titin proteins</p> Signup and view all the answers

    What triggers the secretion of acetylcholine at the axon terminal?

    <p>Action potential and calcium influx</p> Signup and view all the answers

    The region that has myosin thick filaments only is called the ______.

    <p>H-zone</p> Signup and view all the answers

    Match the following components with their descriptions:

    <p>Z-line = Ends of a sarcomere Actin = Thin filaments that attach to Z-lines Myosin = Thick filaments that float in the middle A-band = Region where actin and myosin overlap</p> Signup and view all the answers

    The release of calcium from the sarcoplasmic reticulum is essential for muscle contraction.

    <p>True</p> Signup and view all the answers

    What is the initial step in the crossbridge cycling process?

    <p>Myosin head attaches to actin active site</p> Signup and view all the answers

    What binds to the receptors on the motor end plate of the skeletal muscle plasma membrane?

    <p>Acetylcholine</p> Signup and view all the answers

    The _________ serves as an on/off switch for muscle contraction by binding to calcium.

    <p>troponin</p> Signup and view all the answers

    The M-line is located at the ends of a sarcomere.

    <p>False</p> Signup and view all the answers

    What is formed when a myosin head attaches to an actin active site?

    <p>crossbridge</p> Signup and view all the answers

    What must occur for an action potential to be generated on the sarcolemma?

    <p>Threshold must be reached</p> Signup and view all the answers

    Match the following components with their roles in muscle contraction:

    <p>Acetylcholine = Binds to receptors on the motor end plate Calcium = Exposes active sites on actin Tropomyosin = Prevents crossbridge formation Action Potential = Triggers calcium release from the sarcoplasmic reticulum</p> Signup and view all the answers

    What happens when acetylcholine binds to its receptors?

    <p>It causes a depolarizing graded potential to be generated on the sarcolemma.</p> Signup and view all the answers

    What is the first step in the contraction cycle?

    <p>Sarcoplasmic reticulum releases calcium</p> Signup and view all the answers

    Which process requires oxygen to produce ATP?

    <p>Krebs cycle</p> Signup and view all the answers

    Fatigue occurs due to a lack of ATP and buildup of lactic acid, which is a major cause of muscle soreness.

    <p>False</p> Signup and view all the answers

    What must happen to lactic acid after muscle activity?

    <p>It must be oxidized back to glucose by the liver.</p> Signup and view all the answers

    The breakdown of glycogen is known as __________.

    <p>glycogenolysis</p> Signup and view all the answers

    Match the muscle activity recovery process with its requirement:

    <p>Replacing oxygen in myoglobin = Requires oxygen Replacing creatine phosphate = Requires ATP Oxidizing lactic acid = Requires oxygen Replenishing glycogen = Requires glucose</p> Signup and view all the answers

    What percentage of energy released from glucose breakdown is used for muscle contraction?

    <p>40%</p> Signup and view all the answers

    Anaerobic respiration produces a large amount of ATP.

    <p>False</p> Signup and view all the answers

    What condition occurs after death due to the lack of ATP?

    <p>Rigor mortis</p> Signup and view all the answers

    What is the result of poliomyelitis?

    <p>Destruction of motor neurons</p> Signup and view all the answers

    Muscular dystrophy primarily affects females.

    <p>False</p> Signup and view all the answers

    What is a common effect of tetanus?

    <p>Muscle spasms and rigidity</p> Signup and view all the answers

    Botulism is caused by the toxin produced by __________ in anaerobic conditions.

    <p>Clostridium botulinum</p> Signup and view all the answers

    Match the condition with its primary effect:

    <p>Poliomyelitis = Destroys motor neurons Myasthenia gravis = Destroys motor end plates Botulism = Flaccid paralysis Tetanus = Muscle spasms and rigidity</p> Signup and view all the answers

    Which chemical blocks receptors on the sarcolemma?

    <p>Curare</p> Signup and view all the answers

    Skeletal muscle fibers can undergo mitosis after they have fused into muscle fibers.

    <p>False</p> Signup and view all the answers

    What does the autoimmunity in myasthenia gravis primarily lead to?

    <p>Destruction of ACh receptors</p> Signup and view all the answers

    Study Notes

    Muscle Types

    • Skeletal muscle is striated and voluntary
    • Smooth muscle is not striated and involuntary
    • Cardiac muscle is striated and involuntary

    Muscle Mechanics

    • Muscles pull on lever systems, never push
    • Muscles are arranged in antagonistic pairs (flexors/extensors, abductors/adductors) for opposing movements

    Skeletal Muscle Structure

    • Composed of connective tissue surrounding skeletal muscle fibers
    • Connective tissue bundles muscle fibers into fascicles
    • Fascicles are further divided into individual muscle fibers (cells)
    • Tendons are connective tissue that extends from the muscle to the bone

    Skeletal Muscle Fiber Structure

    • Sarcoplasm: cytoplasm
    • Sarcolemma: plasma membrane with transverse tubules (T-tubules)
    • Sarcoplasmic reticulum (SR): smooth ER that stores calcium
    • Myofibrils: rod-shaped protein structures within the fiber
    • Sarcomeres: functional units of myofibrils, composed of overlapping actin and myosin filaments

    Myofilaments

    • Thin filaments: primarily actin, with troponin and tropomyosin proteins
    • Thick filaments: primarily myosin, with myosin heads capable of forming crossbridges with actin

    Sarcomere Structure

    • Z-lines define the boundaries of each sarcomere
    • Actin filaments attach to Z-lines
    • Myosin filaments are in the center of the sarcomere
    • A-band: region where actin and myosin overlap, is dark
    • I-band: region with only actin filaments, is light
    • H-zone: center of A-band with only myosin
    • M-line: center of the sarcomere

    Sliding Filament Theory

    • Contraction occurs as myosin heads pull on actin filaments, causing them to slide past each other
    • This shortens the sarcomere and the muscle fiber

    Excitation-Contraction Coupling

    • Skeletal muscle contraction is triggered by the nervous system
    • Nerves stimulate the muscle fiber and cause a release of calcium from the SR
    • Calcium allows myosin heads to bind to actin filaments, initiating cross-bridge cycling

    Whole Muscle Contraction

    • Summation: multiple stimuli result in a build-up of tension
    • Incomplete/fused tetanus: high frequency stimulation causes a sustained contraction
    • Recruitment: controlled increase in motor units activated to increase force of contraction

    Muscle Fiber Types

    • Slow-oxidative (SO): slow to fatigue, rich in mitochondria, used for prolonged activity, postural muscles
    • Fast-oxidative-glycolytic (FOG): intermediate in speed, mitochondria and glycogen content. used for endurance activities
    • Fast-glycolytic (FG): fast contracting, high speed, large quantity of glycogen, high power, short durations, used for rapid movements, less mitochondria

    Muscle Metabolism/Energy

    • Energy for muscle contraction comes from ATP
    • Creatine phosphate can rapidly replenish ATP
    • Glycolysis and Oxidative phosphorylation contribute to ATP production, with glycolysis initially providing energy

    Muscle Fatigue

    • Fatigue is due to a buildup of lactic acid and a lack of ATP

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    Description

    This quiz covers essential concepts related to muscle types, their mechanics, and structure. It includes information on skeletal, smooth, and cardiac muscles, as well as the arrangement and functioning of skeletal muscle fibers. Test your understanding of muscle anatomy and physiology!

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