Muscle Anatomy and Physiology Quiz
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Questions and Answers

What is the primary function of skeletal muscle?

  • To allow for body movement by contracting (correct)
  • To transport blood throughout the body
  • To store nutrients and energy
  • To connect bones to other bones

    • What role do tendons play in the musculoskeletal system?

  • Cushioning joints during movement
  • Attaching muscle to bone (correct)
  • Binding bone to bone
  • Connecting muscles to other muscles

    • How does the structure of a muscle fiber contribute to its function?

  • Fibers contain myofibrils which enable contraction (correct)
  • Fibers are filled with fat for energy storage
  • Muscle fibers are composed only of tendons
  • Fibers are tightly bound by ligaments for support

    • What distinguishes isometric contraction from isotonic contraction?

    <p>Isometric produces no change in muscle length, while isotonic changes length</p> Signup and view all the answers

    Which type of muscle is responsible for involuntary movements in organs?

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

    What is a characteristic feature of striated muscle?

    <p>Low endurance</p> Signup and view all the answers

    Which type of muscle is related to smooth muscle but is primarily found in the heart?

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

    What is the purpose of the epimysium in muscle anatomy?

    <p>To bind fascicles together and protect the muscle</p> Signup and view all the answers

    Which statement correctly describes antagonistic muscle pairs?

    <p>One muscle contracts while the other relaxes</p> Signup and view all the answers

    What is the primary role of intercalated discs in cardiac muscle?

    <p>Provide gap junctions for communication</p> Signup and view all the answers

    What is true about smooth muscle?

    <p>It is not under direct nervous control</p> Signup and view all the answers

    What component of muscle fibers is essential for the contractile process?

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

    What constitutes a motor unit?

    <p>One motor neuron and the associated muscle fibers</p> Signup and view all the answers

    How does the number of muscle fibers per motor unit affect muscle control?

    <p>Fewer fibers allow for increased dexterity</p> Signup and view all the answers

    Which type of muscle has no striations and a high endurance capacity?

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

    What is the primary function of the pace-maker in cardiac muscle?

    <p>Initiate the heartbeat</p> Signup and view all the answers

    What is the average number of muscle fibers per motor unit in the human body?

    <p>150 fibers/MU</p> Signup and view all the answers

    What characterizes an isometric contraction?

    <p>Tension increases without a change in muscle length.</p> Signup and view all the answers

    In concentric isotonic contractions, what occurs?

    <p>Muscle shortens and force generated is greater than the load.</p> Signup and view all the answers

    What happens at the neuromuscular junction (NMJ)?

    <p>Nerve and muscle membranes come into close contact.</p> Signup and view all the answers

    What is a key feature of eccentric isotonic contractions?

    <p>They can lead to damage when muscles are overloaded.</p> Signup and view all the answers

    How does asynchronous firing of motor units contribute to muscle contraction?

    <p>It creates a smooth and graded response.</p> Signup and view all the answers

    Which muscle type has the fewest fibers per motor unit?

    <p>Eye muscles</p> Signup and view all the answers

    What is the 'all-or-nothing' response in muscle fibers?

    <p>A fiber either fully contracts or does not contract at all.</p> Signup and view all the answers

    What is the correct duration of the twitch response in a frog after stimulation?

    <p>0.1 sec</p> Signup and view all the answers

    Which phase follows the latent period in muscle contraction?

    <p>Contraction period</p> Signup and view all the answers

    What occurs during the refractory period of muscle contraction?

    <p>Muscle is unable to respond to further stimulation</p> Signup and view all the answers

    What is the duration of the contraction period in a muscle twitch?

    <p>0.04 sec</p> Signup and view all the answers

    What triggers summation in muscle contraction?

    <p>Stimulation while the muscle is still contracting</p> Signup and view all the answers

    What indicates a state of maximal contraction in muscle physiology?

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

    Which mechanism involves increasing the number of motor units to enhance contraction?

    <p>Multiple motor unit summation</p> Signup and view all the answers

    As the impulse frequency increases beyond a certain point, what happens to the twitches?

    <p>They become superimposed and fuse</p> Signup and view all the answers

    What is the primary distinction between the origin and insertion of a muscle?

    <p>Insertion is drawn towards the origin.</p> Signup and view all the answers

    Which of the following best describes the function of skeletal muscles?

    <p>They work in pairs to facilitate movement.</p> Signup and view all the answers

    Which component of a muscle fiber contains the contractile apparatus?

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

    What action occurs during flexion as opposed to extension?

    <p>Flexion closes a joint.</p> Signup and view all the answers

    How do skeletal muscles primarily work in the body?

    <p>They engage in antagonistic pairs to facilitate movement.</p> Signup and view all the answers

    What percentage of the body's total weight is comprised of skeletal muscle?

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

    Which muscle type is specifically associated with the walls of the heart?

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

    What primarily distinguishes isotonic contractions from isometric contractions?

    <p>Isometric contractions generate tension without movement.</p> Signup and view all the answers

    Which characteristic is unique to smooth muscle compared to striated muscle?

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

    What is the duration of the latent period in muscle contraction?

    <p>0.005 seconds</p> Signup and view all the answers

    Which muscle type has centrally placed nuclei?

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

    Which phase of muscle contraction involves the muscle shortening?

    <p>Contraction period</p> Signup and view all the answers

    What distinguishes skeletal muscle from other muscle types?

    <p>Voluntary control</p> Signup and view all the answers

    What can occur if a second stimulation is applied during muscle contraction?

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

    Which term describes the state of maximal contraction when stimuli are applied at high frequency?

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

    How does the motor unit structure contribute to muscular control?

    <p>Fewer muscle fibers per motor unit enhance precision</p> Signup and view all the answers

    Which phenomenon describes increasing the number of motor units involved in muscle contraction?

    <p>Multiple motor unit summation</p> Signup and view all the answers

    Which of the following is true about cardiac muscle?

    <p>It exhibits high endurance</p> Signup and view all the answers

    What time period defines the relaxation phase of muscle contraction in a frog?

    <p>0.05 seconds</p> Signup and view all the answers

    What is the functional significance of the motor unit?

    <p>It consists of a single motor neuron and its associated muscle fibers</p> Signup and view all the answers

    How long does the contraction period last in human muscle physiology?

    <p>0.04 seconds</p> Signup and view all the answers

    What is a common feature of both cardiac and striated muscles?

    <p>Striations present</p> Signup and view all the answers

    During which phase does the muscle not respond to further stimulus following initial stimulation?

    <p>Refractory period</p> Signup and view all the answers

    What type of contraction occurs when a muscle lengthens while tension remains constant?

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

    What is the primary function of asynchronous firing of motor units during muscle contraction?

    <p>To produce a graded response</p> Signup and view all the answers

    Which of the following statements is true regarding isometric muscle contractions?

    <p>Tension in the muscle increases while length remains unchanged</p> Signup and view all the answers

    What describes the connection at the neuromuscular junction (NMJ)?

    <p>It consists of membranes of nerve and muscle cells coming into close contact</p> Signup and view all the answers

    Which statement best describes concentric isotonic contractions?

    <p>The muscle shortens and generates more force than the load</p> Signup and view all the answers

    How does the force generated during eccentric isotonic contractions compare to concentric contractions?

    <p>Eccentric contractions produce more force</p> Signup and view all the answers

    Which muscle type has the fewest fibers per motor unit, allowing for fine motor control?

    <p>Eye muscles</p> Signup and view all the answers

    Study Notes

    Musculoskeletal System, Nervous System & Bioelectricity, MNB.5 Muscle Anatomy and Physiology

    • Learning Outcomes: Students will be able to discuss the three main muscle types (cardiac, smooth, and striated), describe the structure and arrangement of anatomical muscles, outline the innervation of the motor unit, describe the physiology of whole muscle action (including twitch and summation), and differentiate between isometric and isotonic contraction.

    Muscle

    • Composition: About 40% of the body is skeletal muscle. There are approximately 650 skeletal muscles and over 150 surface (anatomical) muscles in the human body.

    Muscle Tissue

    • Definition: Muscle is a tissue with the capability to contract.

    • Tendon: A band of fibrous connective tissue connecting muscle to bone.

    • Ligament: Connects bone to bone.

    Muscle Attachment and Action

    • Origin and Insertion: Muscles are usually attached to two different bones; one attachment is fixed (origin), and the other (insertion) is pulled towards the origin.

    • Action: Movement is a result of multiple muscles working together. Muscle can only contract, not push, and they work in antagonistic pairs (e.g., flexor and extensor). A flexor closes a joint, while an extensor opens a joint.

    Muscle Types

    • Skeletal Muscle: Attached to bones; voluntary; low endurance; striped/striated appearance under direct nervous control.

    • Cardiac Muscle: Found only in the heart; involuntary; high endurance; a type of striated but related to smooth muscle.

    • Smooth Muscle: Found in the walls of digestive tract, blood vessels, bronchus; involuntary; high endurance; not under direct nervous control.

    Muscle Structure

    • Muscle Fibres: Composed of bundles of fascicles. Each fascicle contains many muscle fibers.

    • Myofibrils: Each fiber is composed of smaller fibers, called myofibrils. Myofibrils contain the contractile apparatus (the sarcomere).

    • Epimysium: Loose connective tissue sheath that surrounds the entire muscle.

    Motor Unit (MU)

    • Definition: The functional unit of skeletal muscle.

    • Composition: A single motor neuron and the group of muscle fibers innervated by that neuron.

    • Number of fibers: The number of muscle fibers within a motor unit varies with the required control of the muscle; finer control means fewer fibers per unit. 

    • Neuromuscular Junction (NMJ): Also called the motor endplate; connection between the muscle fiber and the motor neuron; the membranes of the nerve and muscle cells come into close contact; one NMJ per muscle fiber.

    • Muscle Contraction: When a muscle fiber is stimulated at the NMJ, it contracts. The degree of contraction in a whole muscle is a function of the number of motor units stimulated. Maximum contraction is achieved when all motor units fire together. Asynchronous firing of motor units allows for graded response.

    • Muscle Twitch and Summation: The single response of a muscle to a single stimulus. The degree of contraction in a whole muscle varies based on the number of motor units firing together at any given time. Summation is when a rapid second stimulation causes a greater shortening of the muscular response. Frequency of stimulation directly impacts summation and degree of contraction (single twitch, multiple twitch, tetanus).

    Types of Muscle Contractions

    • Isometric Contraction: Muscle contracts but does not shorten; tension on muscle increases and muscle length stays the same.

    • Isotonic Contraction: Muscle length changes while the tension remains constant.

      • Concentric: Muscle shortens.
      • Eccentric: Muscle lengthens.

    Muscle Physiology (Further Details)

    • Whole Muscle Function: Studied via laboratory preparations such as frog's gastrocnemius muscle by stimulating the muscle and measuring its contractions and relaxation.

    • Phases of Contraction: Muscle contraction has three phases: latent period, contraction period, and relaxation period.

    • Refractory period: After initial stimulation there is a short period when muscle will not respond to further stimulus. 

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    Related Documents

    MNB.05 Muscle Anatomy and Physiology PDF

    Description

    Test your understanding of muscle anatomy, including the three main types of muscle: cardiac, smooth, and striated. Explore the structural and functional aspects of muscle tissue and its physiological actions, including contractions and motor unit innervation. This quiz will reinforce your knowledge of muscle attachment and biomechanics.

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