Physiology of Muscle and Levers
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Questions and Answers

Which type of muscle is responsible for voluntary movements?

  • Skeletal Muscle (correct)
  • Striated Muscle
  • Smooth Muscle
  • Cardiac Muscle

    • What unique feature allows cardiac muscle to contract synchronously?

  • Non-striated fibers
  • Intercalated discs (correct)
  • Striated structure
  • Involuntary control

    • In a second-class lever, where is the load positioned?

  • Between the fulcrum and the effort (correct)
  • Between two efforts
  • At one end of the lever
  • At the fulcrum

    • Which of the following muscles is located in the walls of hollow organs?

    <p>Smooth Muscle</p> Signup and view all the answers

    What type of lever is represented by flexing the forearm at the elbow?

    <p>Third-Class Lever</p> Signup and view all the answers

    What characteristic differentiates smooth muscle from skeletal muscle?

    <p>Involuntary operation</p> Signup and view all the answers

    Which type of muscle is exclusively found in the heart?

    <p>Cardiac Muscle</p> Signup and view all the answers

    In a first-class lever, where is the fulcrum located?

    <p>Between the effort and the load</p> Signup and view all the answers

    Which type of muscle fibre is best suited for endurance activities like long-distance running?

    <p>Type I</p> Signup and view all the answers

    What is the primary characteristic of Type IIb muscle fibres?

    <p>They fatigue rapidly and rely mainly on anaerobic metabolism.</p> Signup and view all the answers

    Which type of muscle is responsible for involuntary movements such as pumping blood?

    <p>Cardiac Muscle</p> Signup and view all the answers

    What feature distinguishes smooth muscle from skeletal muscle?

    <p>Smooth muscle cells lack intercalated discs.</p> Signup and view all the answers

    Which type of muscle fibre is characterized by being fast-twitch and moderately resistant to fatigue?

    <p>Type IIa</p> Signup and view all the answers

    How are skeletal muscle contractions primarily controlled?

    <p>By the somatic nervous system</p> Signup and view all the answers

    What is a common function of smooth muscle?

    <p>Regulating blood vessel constriction</p> Signup and view all the answers

    What distinguishes Type I muscle fibres in terms of energy metabolism?

    <p>They have a high reliance on aerobic metabolism.</p> Signup and view all the answers

    What triggers the release of calcium ions from the sarcoplasmic reticulum?

    <p>An action potential</p> Signup and view all the answers

    What role does ATP play in skeletal muscle contraction?

    <p>It provides energy for myosin head movement</p> Signup and view all the answers

    Which protein complex directly regulates the position of tropomyosin on actin?

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

    What is the primary function of myosin during muscle contraction?

    <p>To form cross-bridges with actin</p> Signup and view all the answers

    What happens during the power stroke of muscle contraction?

    <p>ADP and phosphate are released, pulling actin</p> Signup and view all the answers

    What is an isometric contraction?

    <p>A contraction that generates force without extending or shortening</p> Signup and view all the answers

    What initiates the sliding filament theory process?

    <p>Calcium binding to troponin</p> Signup and view all the answers

    What occurs during muscle relaxation?

    <p>Tropomyosin covers binding sites on actin</p> Signup and view all the answers

    What is characteristic of concentric contraction?

    <p>The muscle shortens as it contracts.</p> Signup and view all the answers

    Which energy source is primarily used during the first few seconds of intense muscle activity?

    <p>Creatine phosphate</p> Signup and view all the answers

    What distinguishes complete tetanus from incomplete tetanus?

    <p>Complete tetanus results in sustained contraction with no relaxation.</p> Signup and view all the answers

    What is primarily produced during anaerobic glycolysis?

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

    Which type of muscle fiber is known for high endurance and reliance on aerobic metabolism?

    <p>Type I fibers</p> Signup and view all the answers

    What process occurs in the mitochondria to produce ATP for prolonged low-intensity activities?

    <p>Aerobic respiration</p> Signup and view all the answers

    What happens during summation in muscle contraction?

    <p>Increased force of contraction is observed.</p> Signup and view all the answers

    What defines the characteristic red color of Type I muscle fibers?

    <p>High myoglobin content</p> Signup and view all the answers

    Which of the following describes a third-class lever?

    <p>The effort is between the fulcrum and the load.</p> Signup and view all the answers

    What triggers the release of calcium ions from the sarcoplasmic reticulum during skeletal muscle contraction?

    <p>Action potential traveling down the T-tubules</p> Signup and view all the answers

    Which of the following is not a characteristic of cardiac muscle?

    <p>Multinucleated cells</p> Signup and view all the answers

    Which process produces the most ATP during prolonged muscle activity?

    <p>Aerobic respiration</p> Signup and view all the answers

    What is the primary reason for muscle fatigue in a marathon runner?

    <p>Depletion of muscle glycogen stores</p> Signup and view all the answers

    What role do eccentric contractions play in delayed onset muscle soreness (DOMS)?

    <p>They create microscopic tears in muscle fibers.</p> Signup and view all the answers

    How can a marathon runner improve performance and reduce fatigue?

    <p>Enhancing aerobic capacity and efficiency</p> Signup and view all the answers

    Which statement about Type I muscle fibers is true?

    <p>They are more resistant to fatigue during long-distance running.</p> Signup and view all the answers

    Study Notes

    Physiology of Muscle

    • Muscles are crucial for movement, posture, and vital bodily functions
    • Muscles are classified into three main types: skeletal, cardiac, and smooth
    • Skeletal muscles are attached to bones and responsible for voluntary movements; they are striated and under conscious control
    • Cardiac muscles are found only in the heart, responsible for involuntary pumping of blood; they are striated
    • Smooth muscles are located in the walls of hollow organs (e.g. blood vessels, intestines, bladder), responsible for involuntary movements like peristalsis; they are non-striated

    Levers in the Muscular System

    • Muscles and bones work together via lever systems to create movement
    • Levers are classified into three types based on the relative positions of the fulcrum (joint), effort (muscle force), and load (resistance)
      • First-class lever: fulcrum between effort and load (e.g., head on neck)
      • Second-class lever: load between fulcrum and effort (e.g., standing on tiptoes)
      • Third-class lever: effort between fulcrum and load (e.g., flexing forearm at elbow)

    Physiology of Skeletal Muscle Contraction

    • Skeletal muscle contraction is a complex process involving ATP, calcium ions, and regulatory proteins (tropomyosin and troponin)
      • Sarcomere: Functional unit of skeletal muscle fiber, containing actin and myosin filaments
      • Myosin: Motor protein forming cross-bridges with actin during contraction
      • Actin: Protein forming the backbone of the thin filament, providing binding sites for myosin
      • ATP Binding: ATP binds to myosin head causing detachment from actin
      • ATP Hydrolysis: ATP is hydrolysed providing energy for myosin head to "cock"
      • Cross-Bridge Formation: Myosin binds to actin and release of ADP/phosphate causes powerstroke
      • Calcium Ions (Ca2+): Released from sarcoplasmic reticulum to bind to troponin, moving tropomyosin, exposing myosin-binding sites
      • Troponin & Tropomyosin: Regulatory proteins controlling interaction between actin and myosin
      • Sliding Filament Theory: Myosin heads pull actin filaments towards the center of the sarcomere, shortening the muscle fiber

    Muscle Contraction Types

    • Isometric contraction: Muscle tension increases without a change in length (e.g., holding object)
    • Isotonic contraction: Muscle tension remains constant while the muscle length changes
      • Concentric contraction: Muscle shortens during contraction (e.g., lifting weight)
      • Eccentric contraction: Muscle lengthens during contraction (e.g., lowering weight)

    Muscle Twitch and Summation

    • Muscle twitch: single, brief contraction from a single action potential
    • Summation: increased muscle force from rapid succession of action potentials
    • Incomplete tetanus: muscle fibers do not completely relax before next stimulus
    • Complete tetanus: muscle fiber stimulated at a high frequency, resulting in sustained contraction without relaxation

    Muscle Metabolism

    • Muscle contraction needs energy, primarily from ATP
      • Creatine Phosphate:
        • Phosphate group donated to ADP to regenerate ATP quickly
        • Essential in first few seconds of intense activity
      • Glycolysis:
        • Anaerobic pathway breaking down glucose to produce a small amount of ATP
        • Converts pyruvate to lactate in absence of oxygen, leading to muscle fatigue
      • Aerobic Respiration:
        • Oxidative pathway using glucose, fatty acids, and amino acids in mitochondria to produce large amounts of ATP
        • Necessary for prolonged, lower-intensity activities

    Types of Muscle Fibers

    • Skeletal muscle fibers categorized by speed and metabolic characteristics
      • Type I Fibers (Slow-Twitch, Oxidative): Endurance, aerobic metabolism, suited for long-distance running
      • Type IIa Fibers (Fast-Twitch, Oxidative-Glycolytic): Endurance and power, both aerobic and anaerobic metabolism, suitable for middle-distance running
      • Type IIb Fibers (Fast-Twitch, Glycolytic): Power and speed, anaerobic metabolism, suited to short bursts of activity like sprinting or weightlifting

    Differences Between Muscle Types

    • Skeletal muscle: Striated, voluntary, multiple nuclei per cell
    • Cardiac muscle: Striated, involuntary, one or two nuclei per cell; interconnected by intercalated discs for synchronized contractions
    • Smooth muscle: Non-striated, involuntary, one nucleus per cell; found in hollow organ walls

    Multiple Choice Questions (Examples)

    • Question 1: Which muscle type is most resistant to fatigue and relies primarily on aerobic metabolism? Answer: Type I
    • Question 2: Which lever system describes the effort applied between the fulcrum and the load? Answer: Third-class lever

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    Physiology of Muscle PDF

    Description

    Explore the essential principles of muscle physiology and the role of lever systems in the muscular system. Learn about the three types of muscles—skeletal, cardiac, and smooth—and how they function in movement. Understand how levers enhance the efficiency of these muscular movements.

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