Muscles and Muscle Tissues
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Questions and Answers

What triggers the contraction of the muscle fiber?

  • Action potential (correct)
  • Release of neurotransmitters
  • Ionic balance
  • Calcium ions

    • The process of excitation-contraction coupling directly affects the myofilaments.

    False

    What happens to calcium levels when contraction is complete?

    Calcium levels drop and are reclaimed by the SR.

    The ____-K+ pump restores the ionic conditions of the resting state in muscle fibers.

    <p>Na+</p> Signup and view all the answers

    Match the types of muscle with their key characteristics:

    <p>Skeletal Muscle = Striated and voluntary Cardiac Muscle = Striated and involuntary Smooth Muscle = Non-striated and involuntary</p> Signup and view all the answers

    How much do contracting muscles typically shorten during contraction?

    <p>30-35%</p> Signup and view all the answers

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

    <p>They trigger calcium release.</p> Signup and view all the answers

    The contraction phase of a muscle fiber lasts longer than the action potential that triggers it.

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

    The sliding filament model of contraction mainly refers to the shortening of the muscle fibers.

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

    What do terminal cisterns release during muscle contraction?

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

    What occurs immediately after Ca2+ is released from the SR?

    <p>Calcium binds to troponin, causing shape change and exposing myosin-binding sites.</p> Signup and view all the answers

    The _____ is involved in producing energy used during muscle contraction.

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

    Match each muscle type with its characteristic:

    <p>Cardiac Muscle = Striated and involuntary Smooth Muscle = Non-striated and involuntary Skeletal Muscle = Striated and voluntary All Muscle Types = Generate force through contraction</p> Signup and view all the answers

    What structural feature helps T tubules communicate signals to myofibrils?

    <p>Integral proteins</p> Signup and view all the answers

    Smooth muscle is primarily responsible for voluntary movements in the body.

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

    What role do glycogen granules play in muscle function?

    <p>Energy storage</p> Signup and view all the answers

    What initiates the action potential in a skeletal muscle fiber?

    <p>The release of acetylcholine (ACh) at the neuromuscular junction</p> Signup and view all the answers

    Calcium ions (Ca2+) play a crucial role in triggering muscle contraction.

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

    What is the term for the local depolarization caused by acetylcholine at the neuromuscular junction?

    <p>End plate potential (EPP)</p> Signup and view all the answers

    The action potential travels along the T tubules, causing the sarcoplasmic reticulum to release ______.

    <p>Ca2+</p> Signup and view all the answers

    Match the following muscle types with their characteristics:

    <p>Skeletal Muscle = Voluntary control and striated Cardiac Muscle = Involuntary control and striated Smooth Muscle = Involuntary control and non-striated Cardiac Muscle Structure = Branched and interconnected fibers</p> Signup and view all the answers

    Which step occurs after the end plate potential triggers an action potential?

    <p>Release of calcium from the sarcoplasmic reticulum</p> Signup and view all the answers

    The process of cross bridge cycling is responsible for muscle relaxation.

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

    What is the final trigger for muscle contraction?

    <p>Calcium ions (Ca2+)</p> Signup and view all the answers

    What molecules do muscles utilize to convert the energy of ATP into force?

    <p>Actin and myosin</p> Signup and view all the answers

    Skeletal muscle is primarily responsible for involuntary movements.

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

    What determines the force, velocity, and duration of muscle contraction?

    <p>Factors such as muscle fiber type, load, and the frequency of stimulation determine these characteristics.</p> Signup and view all the answers

    Smooth muscle is involved in ________________ functions within the body.

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

    Match the following muscle types with their key characteristics:

    <p>Skeletal Muscle = Striated and voluntary Smooth Muscle = Non-striated and involuntary Cardiac Muscle = Striated and involuntary</p> Signup and view all the answers

    Which of the following processes is essential for muscles to generate ATP?

    <p>Both A and B</p> Signup and view all the answers

    Calcium ions play no significant role in muscle contraction.

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

    What is the primary characteristic of smooth muscle?

    <p>Smooth muscle is non-striated and involuntary.</p> Signup and view all the answers

    What is meant by the term 'striated' when describing muscle?

    <p>It describes muscles that have a banded or striped appearance.</p> Signup and view all the answers

    Each skeletal muscle fiber is controlled by multiple nerve endings.

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

    What types of tissues is skeletal muscle made up of?

    <p>Muscle fibers, nerves, blood vessels, and connective tissues.</p> Signup and view all the answers

    Skeletal muscles have a rich _____ supply to deliver oxygen and nutrients.

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

    Match the type of muscle with its characteristics:

    <p>Skeletal muscle = Striated and voluntary Cardiac muscle = Striated and involuntary Smooth muscle = Non-striated and involuntary</p> Signup and view all the answers

    What is the primary function of connective tissue sheaths in skeletal muscles?

    <p>To support and reinforce the muscle fibers.</p> Signup and view all the answers

    Skeletal muscle fibers can contract without any nerve stimulation.

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

    Where do blood vessels, nerves, and veins typically enter or exit the muscle?

    <p>Near the central part of the muscle.</p> Signup and view all the answers

    What is the primary protein that makes up thick filaments in muscle cells?

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

    What surrounds a fascicle within a muscle?

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

    The globular heads of myosin are responsible for forming cross bridges with actin during contraction.

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

    Muscle fibers have a striated appearance due to the presence of myofibrils.

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

    What role does ATP play in muscle contraction?

    <p>ATP provides energy for myosin to generate movement.</p> Signup and view all the answers

    The flexible ______ region of myosin connects the head to the tail.

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

    What is the function of the epimysium in muscle structure?

    <p>It covers the entire muscle and provides support.</p> Signup and view all the answers

    The connective tissue that surrounds individual muscle fibers is called ______.

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

    Match the components of the myofilaments with their functions:

    <p>Myosin head = Splits ATP for energy Actin = Forms thin filaments Tropomyosin = Regulates binding sites on actin Troponin = Binds calcium ions</p> Signup and view all the answers

    Which of the following statements is true regarding myosin molecules?

    <p>Myosin splits ATP during muscle contraction.</p> Signup and view all the answers

    Match the muscle components with their descriptions:

    <p>Fascicle = Discrete bundle of muscle cells Myofibril = Rodlike contractile elements within a muscle fiber Muscle fiber = An elongated multinucleate cell Connective tissue wrappings = Layers that surround different organizational levels of muscle</p> Signup and view all the answers

    Which connective tissue layer covers the entire muscle organ?

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

    Thin filaments are primarily composed of myosin proteins.

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

    Myofibrils are primarily involved in the conduction of nerve impulses in muscle cells.

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

    What are the two types of chains that constitute a myosin molecule?

    <p>Heavy chains and light chains.</p> Signup and view all the answers

    What is the primary structural component inside a muscle fiber responsible for contraction?

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

    What causes the local depolarization known as the end plate potential (EPP) in skeletal muscle fibers?

    <p>Binding of ACh to receptors on the muscle fiber</p> Signup and view all the answers

    The action potential (AP) in the sarcolemma directly triggers the release of calcium ions (Ca2+).

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

    What is the role of calcium ions (Ca2+) in muscle contraction?

    <p>Calcium ions bind to troponin, causing a shift in tropomyosin to uncover myosin-binding sites on actin.</p> Signup and view all the answers

    The _____ releases calcium ions in response to an action potential in muscle fibers.

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

    Match the following steps of muscle contraction with their descriptions:

    <ol> <li>End Plate Potential = A. Local depolarization caused by ACh</li> <li>Action Potential = B. Propagation along the sarcolemma</li> <li>Calcium Release = C. Triggering of contraction process</li> <li>Cross Bridge Cycle = D. Interaction of actin and myosin</li> </ol> Signup and view all the answers

    Which of the following best describes the role of T tubules in muscle contraction?

    <p>They transmit action potentials into the muscle fiber.</p> Signup and view all the answers

    Troponin must be bound by calcium ions before muscle contraction can occur.

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

    What is the final trigger for muscle contraction?

    <p>Calcium ions (Ca2+)</p> Signup and view all the answers

    Study Notes

    Overview of muscle types, special characteristics, and functions

    • Muscles use actin and myosin to convert energy from ATP into force
    • Muscles can be skeletal, smooth, or cardiac

    Skeletal Muscle

    • Made up of muscle fibers, nerves, blood vessels, and connective tissues
    • Each skeletal muscle is a discrete organ
    • Every skeletal muscle fiber is supplied with a nerve ending that controls its activity
    • Skeletal muscle has a rich blood supply
    • Connective tissues support the muscle cells and hold the muscle together, preventing it from bursting during strong contractions
    • There are three types of connective tissue:
      • Epimysium: surrounds the entire muscle
      • Perimysium: surrounds each fascicle
      • Endomysium: surrounds each muscle fiber

    Gross anatomy of skeletal muscle

    • Muscles have a nerve, artery, and veins that enter or exit near the central part of the muscle
    • Capillaries follow a long, winding path through the muscle and are numerous, allowing for changes in muscle length

    Microscopic anatomy and sliding filament model of skeletal muscle

    • Actin are thin filaments
    • Myosin are thick filaments
    • Myosin globular heads link to actin to form cross bridges during contraction
    • Myosin itself splits ATP and uses the energy to drive movement

    How does a nerve impulse cause a muscle fiber to contract?

    • The process of excitation-contraction coupling can be broken down into four steps:
      • Neuromuscular junction: The motor neuron releases acetylcholine (ACh) that stimulates the skeletal muscle fiber, causing a local depolarization called an end plate potential (EPP)
      • Muscle fiber excitation: The EPP triggers an action potential (AP) that travels across the entire sarcolemma
      • Excitation-contraction coupling: The AP in the sarcolemma travels down T tubules and causes the release of calcium ions (Ca2+) from the sarcoplasmic reticulum (SR)
      • Cross bridge cycle: Ca2+ binds to troponin, which shifts tropomyosin to uncover the myosin-binding sites on actin. Myosin heads bind actin and contract
    • The contraction is powered by ATP hydrolysis

    What are the properties of whole muscle contraction?

    • Muscle contraction is influenced by:
      • The number of muscle fibers stimulated: More muscle fibers stimulated = stronger contraction
      • The size of the muscle fibers: Larger muscle fibers = stronger contraction
      • Frequency of stimulation: More frequent stimulation = stronger contraction

    How do muscles generate ATP?

    • Muscles generate ATP through:
      • Creatine phosphate pathway: Quickest way to regenerate ATP, but only lasts for 15 seconds.
      • Anaerobic glycolysis: Generates ATP without oxygen but produces lactic acid, quickly becoming unsustainable
      • Aerobic respiration: Most efficient method, but requires oxygen and time to initiate

    What determines the force, velocity, and duration of contraction?

    • Force of contraction depends on:
      • Number of muscle fibers stimulated
      • Muscle fiber size
      • Degree of muscle stretch
    • Velocity of contraction depends on:
      • Muscle fiber type - slow-twitch fibers contract slowly but are resistant to fatigue, fast-twitch fibers contract rapidly and forcefully
      • Load: heavier loads = slower contraction
    • Duration of contraction depends on:
      • Muscle fiber type
      • Load: heavier loads = shorter contraction duration

    How does skeletal muscle respond to exercise?

    • Exercise results in:
      • Increased muscle mass
      • Improved muscle efficiency
      • Increased blood supply to muscles

    Smooth Muscle

    • Found in walls of hollow organs
    • Structure:
      • Spindle-shaped, nonstriated, and uninucleate
      • Contain actin and myosin, but not arranged into sarcomeres
      • No T-tubules, but SR is less developed
    • Involuntary
    • Contraction:
      • Contracts more slowly and over a wider range of lengths than skeletal muscle
    • Types:
      • Single-unit smooth muscle: Fibers are interconnected by gap junctions and function as a unit
      • Multi-unit smooth muscle: Fibers are independent and innervated by autonomic nerves

    Developmental Aspects of Muscles

    • The development of muscles starts in the embryo
    • Skeletal muscle fibers: Formed from fusion of myoblasts
    • Smooth and cardiac muscle fibers: Formed from division of existing muscle cells

    How does smooth muscle differ from skeletal muscle?

    • Smooth muscle:
      • Nonstriated
      • Involuntary
      • Found in hollow organs
      • Contracts more slowly and over a wider range of lengths than skeletal muscle
    • Skeletal muscle:
      • Striated
      • Voluntary
      • Attached to bones
      • Contracts rapidly and forcefully

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    Chapter 9 - Muscles and Muscle Tissue PDF

    Description

    Test your knowledge of muscle fiber contraction and the processes involved in excitation-contraction coupling. This quiz will cover key concepts such as calcium levels, muscle types, and the structure of muscle cells. Perfect for students studying anatomy and physiology!

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