Muscle Contraction Process Quiz
36 Questions
3 Views

Choose a study mode

Play Quiz
Study Flashcards
Spaced Repetition
Chat to lesson

Podcast

Play an AI-generated podcast conversation about this lesson

Questions and Answers

What is the role of calcium in the excitation-contraction coupling of cardiac muscle?

  • Propagates the action potential to dyads
  • Binds to myofibrils during contraction (correct)
  • Causes relaxation by returning to the sarcoplasmic reticulum
  • Generates action potential in pacemaker cells
  • How does the length of the contractile cell action potential in cardiac muscle prevent tetanus?

  • By having a prolonged refractory period (correct)
  • By propagating action potentials slowly
  • By inhibiting the binding of calcium to myofibrils
  • By releasing an insufficient amount of calcium
  • How does the resting sarcomere length in cardiac muscle compare to optimal length?

  • It varies depending on muscle contractility
  • It is greater than optimal length
  • It is at optimal length
  • It is less than optimal length (correct)
  • What differentiates cardiac muscle from skeletal muscle regarding contraction?

    <p>It has higher passive tension due to blood filling</p> Signup and view all the answers

    Which statement best describes the excitation-contraction coupling of skeletal muscle?

    <p>Dependent on calcium binding to myofibrils</p> Signup and view all the answers

    What effect does the blood filling in the ventricles have on cardiac muscle?

    <p>Increases passive tension due to stretching</p> Signup and view all the answers

    What type of muscle fiber has physiological and histological features intermediate between the other two types?

    <p>Fast oxidative-glycolytic (Type II a, FOG) fibers</p> Signup and view all the answers

    Which type of cells in the heart are responsible for initiating action potentials?

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

    What is the function of intercalated disks in cardiac muscle cells?

    <p>Facilitate electrical coupling between cardiac myocytes</p> Signup and view all the answers

    What is the primary role of pacemaker cells in the heart's conduction system?

    <p>Generating and conducting electrical impulses</p> Signup and view all the answers

    Which component is significantly less developed in cardiac muscle cells compared to skeletal muscle fibers?

    <p>Endoplasmic reticulum</p> Signup and view all the answers

    What percentage of myocardial cells are made up of pacemaker cells in the heart?

    <p>Around 1-5%</p> Signup and view all the answers

    What is the correct sequence of events at the neuromuscular junction for skeletal muscle contraction?

    <p>Excitation, coupling, contraction, relaxation</p> Signup and view all the answers

    What is the result of calcium binding to the myofibrils during skeletal muscle contraction?

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

    What happens when calcium is released from the myofibrils during skeletal muscle relaxation?

    <p>Calcium returns to the sarcoplasmic reticulum</p> Signup and view all the answers

    What occurs when action potentials are propagated down the somatic motor neuron at the neuromuscular junction?

    <p>Depolarization of presynaptic terminal</p> Signup and view all the answers

    What role do nicotinic receptors play at the motor-end plate during skeletal muscle contraction?

    <p>Binding acetylcholine</p> Signup and view all the answers

    What is the effect of the end plate potential spreading across the muscle fiber during skeletal muscle contraction?

    <p>Depolarization and firing of an action potential</p> Signup and view all the answers

    What happens at the end of the power stroke in muscle contraction?

    <p>Myosin releases ADP</p> Signup and view all the answers

    In skeletal muscle, what induces a conformational change in the thin filament allowing myosin heads to cross-bridge with actin?

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

    Which statement best describes an isotonic contraction?

    <p>Muscle tension stays constant and the muscle fiber shortens</p> Signup and view all the answers

    What is the role of afterload in the force-velocity relationship in muscle contraction?

    <p>Afterload decreases velocity of shortening</p> Signup and view all the answers

    What happens during temporal summation in muscle contraction?

    <p>Second contraction starts before first relaxes</p> Signup and view all the answers

    In skeletal muscle, what is the primary function of spatial summation?

    <p>Enhance force through multiple motor unit recruitment</p> Signup and view all the answers

    At what stage does ATP binding destabilize the myosin-actin interaction in muscle contraction?

    <p>&quot;Power stroke&quot;</p> Signup and view all the answers

    What defines the length-tension relationship in muscle mechanics?

    <p>&quot;Overlap between actin and myosin filaments&quot;</p> Signup and view all the answers

    Which type of muscle tissue makes up approximately 30-45% of the total body weight?

    <p>Skeletal muscle</p> Signup and view all the answers

    What is the function of the perimysium in skeletal muscle organization?

    <p>Enclose the muscle fibers known as fascicles</p> Signup and view all the answers

    Which protein wraps around actin filaments and covers the myosin-binding sites in sarcomeres?

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

    What is the function of troponin-I (Tn-I) in sarcomeres during muscle contraction?

    <p>Inhibit myosin binding site on actin</p> Signup and view all the answers

    Where are triads located in skeletal and cardiac muscle cells?

    <p>Terminal cisternae and T-tubules</p> Signup and view all the answers

    In skeletal muscle, what is the primary function of nebulin and titin?

    <p>Support actin strands</p> Signup and view all the answers

    Which region of the sarcomere contains only thick (myosin) filaments?

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

    What is the primary function of the endomysium in skeletal muscle organization?

    <p>Enclose the skeletal muscle cells or myofibrils</p> Signup and view all the answers

    Which organelle serves as a major store for calcium in muscle cells?

    <p>Sarcoplasmic reticulum (SR)</p> Signup and view all the answers

    What is the primary function of transverse tubules (T-tubules) in muscle cells?

    <p>Conduct action potentials rapidly throughout the muscle</p> Signup and view all the answers

    Study Notes

    Skeletal Muscle Organization

    • Skeletal muscles make up 30-45% of total body weight
    • Under voluntary control and mostly attached to bones
    • Functions: produce skeletal movement, maintain posture and body position, protect internal organs, and generate heat
    • Three connective tissue layers: epimysium, perimysium, and endomysium
    • Each skeletal muscle fiber has a sarcolemma (cell membrane), transverse tubules (T-tubules), and a sarcoplasmic reticulum (SR)

    Sarcomere Structure

    • Sarcomeres are the contractile units of skeletal and cardiac muscle
    • A-band contains thick (myosin) and thin filaments (actin)
    • I-band contains only thin filaments
    • Z-line anchors thin filaments to the sarcolemma
    • H-zone contains only thick filaments
    • Sarcomeres shorten during muscle contraction

    Actin Filaments

    • Actin chains are intertwined with troponin and tropomyosin proteins
    • Actin has a myosin-binding site
    • Troponin and tropomyosin regulate muscle contraction

    Myosin Filaments

    • Myosin molecules form a protein chain with a head and a tail
    • Myosin head has a heavy chain (HC) and a light chain (LC)
    • Heavy chain contains an ATP binding site and a binding site for actin
    • Elastic hinge region allows the head to swivel and move (power stroke)

    Excitation-Contraction Coupling

    • Excitation-contraction coupling is the process in which an action potential causes calcium concentration to increase in the cytosol, leading to contraction of the muscle
    • Steps: excitation, coupling, contraction, and relaxation
    • Calcium binds to troponin and tropomyosin, allowing myosin heads to cross-bridge with actin

    Neuromuscular Junction

    • The neuromuscular junction is the synapse between a motor neuron and a muscle fiber
    • Sequence of events: action potential propagation, calcium influx, ACh release, binding to nicotinic receptors, and muscle contraction

    Muscle Contraction and Relaxation

    • Muscle twitch: one cycle of excitation-contraction coupling
    • Types of contraction: isometric (no shortening) and isotonic (shortening with constant tension)
    • Types of isotonic contractions: concentric (shortening) and eccentric (lengthening)
    • Length-tension relationship: the relationship between fiber length and force produced
    • Force-velocity relationship: the velocity of shortening as a product of changes in afterload

    Cardiac Muscle

    • The heart is a hollow muscular pump that pumps blood throughout the vasculature
    • Ventricular muscle cells: striated muscle cells with two nuclei, rich in mitochondria, and less developed SR
    • Cells are connected end-to-end by gap junctions, forming a functional syncytium
    • Pacemaker cells initiate action potentials necessary for cardiac muscle contraction

    Excitation-Contraction Coupling in Cardiac Muscle

    • Similar to skeletal muscle, but with differences in SR and calcium release
    • No tetanus in cardiac muscle due to the length of the contractile cell action potential
    • Graded contractions possible due to the heart's ability to increase contractile force under changing conditions

    Studying That Suits You

    Use AI to generate personalized quizzes and flashcards to suit your learning preferences.

    Quiz Team

    Related Documents

    Description

    Test your knowledge on the muscle contraction process. From myosin releasing ADP to ATP binding destabilizing the myosin-actin interaction, each step is crucial for muscle fiber shortening.

    More Like This

    Use Quizgecko on...
    Browser
    Browser