Muscle Tissue Overview
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Muscle Tissue Overview

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Questions and Answers

What is the primary function of the sarcoplasmic reticulum in muscle fibers?

  • Produce energy for muscle contractions
  • Store and release calcium ions (correct)
  • Facilitate the exchange of oxygen in muscle tissues
  • Provide structural support to the muscle fibers

    • Which proteins are primarily found in thick myofilaments?

  • Actin and Tropomyosin
  • Myoglobin and Actin
  • Myosin and its heads (correct)
  • Tropomyosin and Troponin

    • What structure defines the boundary of a sarcomere?

  • Z-discs (correct)
  • I-band
  • A-band
  • M-line

    • What happens to tropomyosin during muscle contraction?

    <p>It exposes myosin binding sites on actin</p> Signup and view all the answers

    How are sarcomeres organized within a myofibril?

    <p>Connected end to end</p> Signup and view all the answers

    What is the primary function of cardiac muscle?

    <p>To pump blood through the circulatory system</p> Signup and view all the answers

    Which structural feature distinguishes cardiac muscle from skeletal muscle?

    <p>Intercalated discs</p> Signup and view all the answers

    Which type of muscle tissue is responsible for goosebumps and moving food through the digestive tract?

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

    What allows cardiac muscle cells to contract in a coordinated manner?

    <p>Gap junctions within intercalated discs</p> Signup and view all the answers

    How do skeletal muscles differ from cardiac muscles in terms of structure?

    <p>Skeletal muscles have multiple nuclei.</p> Signup and view all the answers

    Which characteristic is NOT associated with smooth muscle tissue?

    <p>Striated appearance</p> Signup and view all the answers

    What is the primary function of muscle contractility?

    <p>To facilitate movement through contraction and relaxation</p> Signup and view all the answers

    What role do pacemaker cells have in cardiac muscle tissue?

    <p>They control the rate of cardiac contractions.</p> Signup and view all the answers

    Which characteristic allows muscles to return to their resting length after stretching?

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

    What is a prominent feature of smooth muscle in terms of its structure?

    <p>It consists of non-striated cells with one nucleus.</p> Signup and view all the answers

    What is a key function of skeletal muscles in maintaining posture?

    <p>Continuous partial contraction</p> Signup and view all the answers

    What process contributes to heat production in skeletal muscles?

    <p>Catabolic processes</p> Signup and view all the answers

    Which process describes the ability of muscles to respond to regulatory signals from nerves?

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

    Which of the following is NOT a characteristic of all muscle tissues?

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

    How do muscles produce movement?

    <p>By pulling on bones</p> Signup and view all the answers

    Which function of skeletal muscle is primarily responsible for maintaining homeostasis?

    <p>Heat production</p> Signup and view all the answers

    What is the primary function of creatine phosphate in muscle cells?

    <p>To transfer phosphate to ADP to form ATP</p> Signup and view all the answers

    How long can creatine phosphate provide energy during intense exercise?

    <p>Up to 15 seconds</p> Signup and view all the answers

    Which process primarily produces the majority of ATP in muscle cells?

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

    What do smaller motor units typically allow for in muscle control?

    <p>Fine motor control</p> Signup and view all the answers

    What is a characteristic of larger motor units?

    <p>They control thousands of muscle fibers.</p> Signup and view all the answers

    In what order are motor units typically recruited during muscle contraction?

    <p>Smaller motor units first, then larger</p> Signup and view all the answers

    What is the recruitment process in muscle physiology?

    <p>Organizing the activation of motor units</p> Signup and view all the answers

    Which type of neuron is responsible for innervating small motor units?

    <p>Lower-threshold neurons</p> Signup and view all the answers

    What initiates the process of muscle contraction?

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

    Which ion is primarily responsible for the depolarization of the muscle fiber membrane?

    <p>Sodium ions</p> Signup and view all the answers

    Which step occurs immediately after myosin binds to actin?

    <p>ADP and inorganic phosphate are released</p> Signup and view all the answers

    What causes muscle relaxation after contraction?

    <p>The cessation of nerve signal and ach release</p> Signup and view all the answers

    What happens to the myosin head after the power stroke?

    <p>It detaches when ATP attaches</p> Signup and view all the answers

    Which substance is necessary for sustaining muscle contraction during repetitive cycles?

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

    What leads to rigor mortis in skeletal muscles?

    <p>Low energy ATP levels</p> Signup and view all the answers

    What role does the sarcoplasmic reticulum play in muscle contraction?

    <p>It releases calcium ions during excitation</p> Signup and view all the answers

    Which part of the muscle fiber is responsible for action potential propagation?

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

    What is the function of ATP during the cross-bridge cycling?

    <p>It provides energy to myosin for the power stroke</p> Signup and view all the answers

    At muscle relaxation, what happens to tropomyosin?

    <p>It covers myosin binding sites</p> Signup and view all the answers

    What is the power stroke in muscle contraction?

    <p>The pivoting motion of the myosin head</p> Signup and view all the answers

    What triggers the opening of voltage-gated calcium channels?

    <p>Action potential from the muscle fiber</p> Signup and view all the answers

    Which of the following is NOT involved in the muscle contraction process?

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

    Study Notes

    Muscle Tissue Overview

    • Muscle tissue is excitable, contractile, extensible, and elastic
    • Muscle tissue functions in movement, posture, heat production, and protection
    • There are three types of muscle tissue: skeletal, cardiac, and smooth

    Skeletal Muscle

    • Skeletal muscle is responsible for movement of the skeleton
    • Skeletal muscle is multinucleated with a regular arrangement of actin and myosin fibers, resulting in striations
    • Skeletal muscle is usually connected to bones or fascia

    Cardiac Muscle

    • Cardiac muscle is responsible for pumping blood through the circulatory system
    • Cardiac muscle cells are branched and contain 1-2 nuclei
    • Cardiac muscle has intercalated discs that allow for coordinated contraction
    • Intercalated discs contain gap junctions and desmosomes
    • Gap junctions allow for rapid depolarization of cardiac muscle cells, creating a functional syncytium

    Smooth Muscle

    • Smooth muscle is responsible for various functions such as goosebumps, food movement in the digestive tract, and blood flow regulation
    • Smooth muscle cells contain a single nucleus and lack regular arrangement of actin and myosin fibers

    Sarcomere

    • The sarcomere is the functional unit of skeletal muscle fibers
    • It is a 3D cylinder with striations due to the arrangement of actin and myosin myofilaments
    • Each myofibril can contain hundreds to thousands of sarcomeres

    Myofilaments

    • Myofibrils contain thousands of thick and thin myofilaments
    • Myofilaments are made up of actin, myosin, tropomyosin, and troponin
    • Thin filaments contain actin with myosin-binding sites
    • Thick filaments contain myosin heads which bind to actin

    Neuromuscular Junction (NMJ)

    • Each skeletal muscle fiber is innervated by a motor neuron at the NMJ
    • A signal from the motor neuron can cause muscle contraction

    Contraction of Skeletal Muscle

    • An action potential reaches the end of the motor neuron, releasing acetylcholine (ACh)
    • ACh binds to receptors on skeletal muscle fibers, opening sodium channels
    • Sodium enters the sarcoplasm, changing the membrane potential
    • The action potential travels along the sarcolemma and into the cell through T-tubules
    • The action potential depolarizes the cell membrane, triggering the release of calcium ions (Ca++) from the sarcoplasmic reticulum (SR)
    • Ca++ binds to troponin, moving the troponin-tropomyosin complex and exposing myosin-binding sites on actin
    • Myosin heads bind to actin, forming cross-bridges
    • Myosin heads pivot towards the center of the sarcomere, causing a power stroke
    • ATP attaches to the myosin head, detaching the cross-bridge
    • The myosin head re-cocks using energy from ATP hydrolysis
    • The cycle of power stroke, detachment, and re-cocking continues as long as Ca++ is present

    Relaxation of a Muscle Fiber

    • Nerve signal stops, halting ACh release
    • Sodium channels close, repolarizing the sarcolemma and T-tubules
    • Ca++ channels in the SR close, and Ca++ is pumped back into the SR using ATP
    • Tropomyosin moves back to cover the myosin-binding sites on actin
    • The interaction between thick and thin filaments relaxes

    Sources of ATP

    • Skeletal muscle has limited ATP stores
    • ATP is quickly replaced through creatine phosphate, glycolysis, and aerobic respiration
    • Creatine phosphate provides a short burst of energy (15 seconds)
    • Glycolysis provides energy for about 1 minute
    • Aerobic respiration provides 95% of ATP and is more efficient

    Motor Units

    • Each skeletal muscle fiber is innervated by one motor neuron
    • One motor neuron can innervate multiple muscle fibers, depending on the muscle's function
    • Small motor units control fine movements with smaller motor neurons
    • Larger motor units control gross movements with larger motor neurons
    • Recruitment of motor units increases muscle contraction strength: allows for variation in force generation.

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    Description

    Explore the fascinating world of muscle tissue with this quiz! Learn about the characteristics and functions of skeletal, cardiac, and smooth muscle. Discover how each type contributes to movement, circulation, and bodily functions.

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