Myofilaments and Muscle Contraction
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Questions and Answers

Which type of muscle is controlled consciously and attached to the skeleton?

  • Skeletal muscle (correct)
  • Smooth muscle
  • Cardiac muscle
  • None of the above

    • Which type of muscle is found in the walls of blood vessels and internal organs?

  • Skeletal muscle
  • Smooth muscle (correct)
  • Cardiac muscle
  • None of the above

    • Which type of muscle is only found in the heart?

  • Skeletal muscle
  • Smooth muscle
  • Cardiac muscle (correct)
  • None of the above

    • Which property of muscles allows them to be stretched or lengthened beyond their resting length?

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

    Which property of muscles allows them to return to their original shape after being stretched or contracted?

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

    Which property of muscles enables them to generate tension by contracting or shortening?

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

    Which organelle is responsible for storing, releasing, and reuptake of calcium ions in a muscle fiber?

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

    What is the function of T-tubules in a muscle fiber?

    <p>Allow for rapid transmission of the action potential into the cell</p> Signup and view all the answers

    Which protein is responsible for binding both ATP and actin in a muscle fiber?

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

    Which component of a myosin filament forms cross-bridges with actin to shorten the sarcomere?

    <p>Myosin heads</p> Signup and view all the answers

    Which protein complex is composed of actin, tropomyosin, and troponin in a muscle fiber?

    <p>Thin filament</p> Signup and view all the answers

    Which type of muscle fiber has more mitochondria and is responsible for slow-twitch contractions?

    <p>Red fibers</p> Signup and view all the answers

    Which type of muscle fiber has a high aerobic capacity and fatigue resistance?

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

    Which type of muscle fiber has a moderate aerobic capacity and high anaerobic capacity?

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

    Which type of muscle fiber has a low aerobic capacity and high anaerobic capacity?

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

    What is the primary function of satellite cells in skeletal muscles?

    <p>Repair damaged muscle fibers</p> Signup and view all the answers

    What is the primary function of myostatin in muscle biology?

    <p>Regulate muscle growth and development</p> Signup and view all the answers

    Which type of muscle action is responsible for elbow flexion?

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

    Which property is not associated with muscle fibers?

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

    What is the primary function of skeletal muscles?

    <p>To enable movement of the body</p> Signup and view all the answers

    What is the role of the epimysium?

    <p>To surround the entire muscle</p> Signup and view all the answers

    What is the basic contractile unit of striated muscle fibers?

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

    What is the function of the T-tubules in muscle cells?

    <p>To invaginate into the sarcoplasm</p> Signup and view all the answers

    What are the two types of muscle fibers?

    <p>Slow fibers and Fast fibers</p> Signup and view all the answers

    According to the Sliding Filament Model of Muscle Contraction, how does a muscle shorten or lengthen?

    <p>The thick and thin filaments change length</p> Signup and view all the answers

    What happens when calcium ions bind to the troponin-tropomyosin complex?

    <p>The cross bridge is formed</p> Signup and view all the answers

    What is the source of energy for muscle action?

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

    What causes the actin filaments to slide toward the M line during muscle contraction?

    <p>The myosin heads bend toward the center of the sarcomere</p> Signup and view all the answers

    What type of muscle fibers have high aerobic endurance and are suited to low-intensity endurance activities?

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

    What type of muscle fibers are better for anaerobic or explosive activities?

    <p>Type II (White)</p> Signup and view all the answers

    Which type of stimuli can smooth muscle respond to?

    <p>All of the above</p> Signup and view all the answers

    What type of nervous system signals does smooth muscle receive?

    <p>Both sympathetic and parasympathetic nervous system signals</p> Signup and view all the answers

    How is smooth muscle organized?

    <p>Into sheets</p> Signup and view all the answers

    What are the physical dimensions of smooth muscle determined by?

    <p>All of the above</p> Signup and view all the answers

    Which of the following is NOT a factor that smooth muscle can respond to?

    <p>Hydrogen gas levels</p> Signup and view all the answers

    What is the primary function of smooth muscle?

    <p>To regulate digestion</p> Signup and view all the answers

    Which type of muscle is smooth muscle?

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

    What are the dimensions of smooth muscle determined by?

    <p>All of the above</p> Signup and view all the answers

    Which type of muscle receives nerve signals from the autonomic nervous system?

    <p>All of the above</p> Signup and view all the answers

    What enables coordinated contractions in smooth muscle?

    <p>Bundles or sheets</p> Signup and view all the answers

    What is the main function of smooth muscle in the gastrointestinal tract?

    <p>Peristaltic contraction</p> Signup and view all the answers

    Which type of smooth muscle is found in the ciliary muscles of the eyes?

    <p>Multi-unit smooth muscle</p> Signup and view all the answers

    What is the main difference between smooth muscle and skeletal muscle in terms of actin and myosin arrangement?

    <p>Smooth muscle has myosin filaments attached to dense bodies</p> Signup and view all the answers

    What is the main source of Ca2+ for smooth muscle contraction?

    <p>Extra cellular fluid</p> Signup and view all the answers

    Which type of muscle fiber has the highest aerobic capacity and fatigue resistance?

    <p>Slow-twitch muscle fibers</p> Signup and view all the answers

    What is the main function of the iris muscle in the eyes?

    <p>Pupil constriction and dilation</p> Signup and view all the answers

    What is the main function of smooth muscle in the walls of blood vessels?

    <p>Regulation of blood flow</p> Signup and view all the answers

    Which property of smooth muscle allows it to contract as much as 80% of its length?

    <p>Side-polar cross-bridges in myosin filaments</p> Signup and view all the answers

    What is the main function of smooth muscle in the uterus?

    <p>Contraction during childbirth</p> Signup and view all the answers

    What is the main function of smooth muscle in the base of hair follicles?

    <p>Hair erection</p> Signup and view all the answers

    Which organelle is responsible for storing, releasing, and reuptake of calcium ions in smooth muscle cells?

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

    What is the role of calmodulin in smooth muscle contraction?

    <p>To regulate the contraction process</p> Signup and view all the answers

    Which enzyme is activated by calmodulin in smooth muscle contraction?

    <p>Myosin light chain kinase (MLCK)</p> Signup and view all the answers

    What is the role of myosin light chain kinase (MLCK) in smooth muscle contraction?

    <p>To phosphorylate myosin</p> Signup and view all the answers

    What happens when the ion calcium concentration is reduced in smooth muscle cells?

    <p>Myosin phosphatase removes phosphate from myosin</p> Signup and view all the answers

    Which type of muscle uses calmodulin as a calcium-binding protein to regulate the contraction process?

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

    Which component of a myosin filament forms cross-bridges with actin to shorten the sarcomere?

    <p>Myosin heads</p> Signup and view all the answers

    What is the primary function of satellite cells in smooth muscles?

    <p>To repair and regenerate muscle tissue</p> Signup and view all the answers

    What is the role of caveolae in smooth muscle cells?

    <p>To excite calcium release from the SR</p> Signup and view all the answers

    Which type of muscle fiber has a low aerobic capacity and high anaerobic capacity?

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

    Which type of muscle receives nerve signals from the autonomic nervous system?

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

    What is the main function of smooth muscle in the uterus?

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

    What are the dimensions of smooth muscle determined by?

    <p>Physical factors</p> Signup and view all the answers

    What enables coordinated contractions in smooth muscle?

    <p>Neural factors</p> Signup and view all the answers

    What is the role of caveolae in smooth muscle cells?

    <p>Cellular communication</p> Signup and view all the answers

    What type of stimuli can smooth muscle respond to?

    <p>All of the above</p> Signup and view all the answers

    What is the source of energy for muscle action?

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

    What is the role of myosin light chain kinase (MLCK) in smooth muscle contraction?

    <p>Activating myosin cross-bridges</p> Signup and view all the answers

    What happens when the ion calcium concentration is reduced in smooth muscle cells?

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

    Which organelle is responsible for storing, releasing, and reuptake of calcium ions in a muscle fiber?

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

    Which of the following is true about smooth muscle contraction?

    <p>Calcium-bound calmodulin activates myosin light chain kinase (MLCK).</p> Signup and view all the answers

    Which organelle is responsible for calcium release in smooth muscle cells?

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

    What is the role of caveolae in smooth muscle cells?

    <p>They are small invaginations of the cell membrane.</p> Signup and view all the answers

    Which type of muscle uses troponin as a calcium-binding protein?

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

    Which enzyme is responsible for phosphorylating myosin in smooth muscle cells?

    <p>Myosin light chain kinase (MLCK)</p> Signup and view all the answers

    What happens when myosin is phosphorylated in smooth muscle cells?

    <p>Myosin binds to actin, causing muscle contraction.</p> Signup and view all the answers

    Which type of muscle fiber has the highest aerobic capacity and fatigue resistance?

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

    What is the primary function of myosin phosphatase in smooth muscle cells?

    <p>To remove phosphate from myosin</p> Signup and view all the answers

    Which muscle type uses calmodulin as a calcium-binding protein?

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

    What is the role of the sarcoplasmic reticulum in smooth muscle contraction?

    <p>To store and release calcium ions</p> Signup and view all the answers

    What is the main difference between single-unit smooth muscle and multi-unit smooth muscle?

    <p>Single-unit smooth muscle fibers are arranged in sheets or bundles, while multi-unit smooth muscle fibers are discrete and separate</p> Signup and view all the answers

    Which muscles are examples of single-unit smooth muscle?

    <p>Gastrointestinal tract and bile ducts</p> Signup and view all the answers

    How do smooth muscle cells contract?

    <p>Through the sliding filament mechanism</p> Signup and view all the answers

    What is the role of the sarcoplasmic reticulum in smooth muscle contraction?

    <p>It regulates the binding of calcium to calmodulin in smooth muscle cells</p> Signup and view all the answers

    What is the function of caveolae in smooth muscle cells?

    <p>To regulate the contraction process by binding calcium ions</p> Signup and view all the answers

    What is the main function of smooth muscle in the uterus?

    <p>Contraction during childbirth and menstruation</p> Signup and view all the answers

    What is the main difference between smooth muscle and skeletal muscle in terms of contraction?

    <p>Smooth muscle can contract as much as 80% of its length, while skeletal muscle can only contract up to 30% of its length</p> Signup and view all the answers

    What is the role of myosin light chain kinase (MLCK) in smooth muscle contraction?

    <p>To phosphorylate myosin and initiate cross-bridge cycling</p> Signup and view all the answers

    What is the main function of smooth muscle in the gastrointestinal tract?

    <p>Peristaltic contraction</p> Signup and view all the answers

    What enables coordinated contractions in smooth muscle?

    <p>The presence of many gap junctions between muscle cells</p> Signup and view all the answers

    Study Notes

    Muscle Types

    • Skeletal muscle is controlled consciously and attached to the skeleton
    • Smooth muscle is found in the walls of blood vessels and internal organs
    • Cardiac muscle is only found in the heart

    Muscle Properties

    • Elasticity is the property that allows muscles to be stretched or lengthened beyond their resting length
    • Elasticity is the property that allows muscles to return to their original shape after being stretched or contracted
    • Contractility is the property that enables muscles to generate tension by contracting or shortening

    Muscle Fiber Components

    • The sarcoplasmic reticulum is responsible for storing, releasing, and reuptake of calcium ions in a muscle fiber
    • T-tubules are involved in the function of a muscle fiber
    • Actin and myosin are proteins in a muscle fiber
    • Myosin is responsible for binding ATP and actin in a muscle fiber
    • The component of a myosin filament that forms cross-bridges with actin to shorten the sarcomere is the myosin head
    • Actin, tropomyosin, and troponin form a complex in a muscle fiber

    Muscle Fiber Types

    • Slow-twitch (Type I) muscle fibers have more mitochondria and are responsible for slow-twitch contractions
    • Fast-twitch (Type II) muscle fibers have a high anaerobic capacity
    • Intermediate (Type IIa) muscle fibers have a moderate aerobic capacity and high anaerobic capacity

    Muscle Functions

    • The primary function of satellite cells in skeletal muscles is to repair and regenerate muscle tissue
    • The primary function of myostatin in muscle biology is to inhibit muscle growth and development
    • The primary function of skeletal muscles is to provide movement, maintain posture, and regulate body temperature
    • The role of the epimysium is to surround and protect the entire muscle
    • The basic contractile unit of striated muscle fibers is the sarcomere

    Smooth Muscle Functions

    • Smooth muscle receives nerve signals from the autonomic nervous system
    • The primary function of smooth muscle is to control the diameter of blood vessels, regulate body temperature, and aid in digestion
    • Smooth muscle can respond to hormonal, neural, and local stimuli
    • Smooth muscle is organized into single-unit and multi-unit types
    • The physical dimensions of smooth muscle are determined by the length and diameter of the muscle fibers
    • The primary function of smooth muscle in the gastrointestinal tract is to mix food with digestive enzymes
    • The primary function of smooth muscle in the uterus is to aid in childbirth
    • The primary function of smooth muscle in the base of hair follicles is to regulate hair growth

    Smooth Muscle Contraction

    • Smooth muscle contraction is regulated by calcium ions and calmodulin
    • The enzyme myosin light chain kinase (MLCK) is activated by calmodulin to phosphorylate myosin
    • Phosphorylated myosin then interacts with actin to shorten the sarcomere
    • The sarcoplasmic reticulum is responsible for storing, releasing, and reuptake of calcium ions in smooth muscle cells
    • The role of caveolae is to regulate the contraction process by modulating calcium release

    Muscle Comparisons

    • Smooth muscle differs from skeletal muscle in terms of actin and myosin arrangement
    • Smooth muscle can contract as much as 80% of its length due to its unique properties

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    Description

    Test your knowledge on myofilaments and their role in muscle contraction with this quiz. Learn about the components of thin and thick filaments, the arrangement of filaments in a sarcomere, and the structure of myosin molecules.

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