Muscle Anatomy and Physiology Quiz
56 Questions
5 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 primary function of muscles needing oxygen after exercise?

  • To reduce fatigue immediately
  • To increase muscle size
  • To replenish myoglobin and convert lactic acid back to glucose (correct)
  • To produce ATP only

    • Fast glycolytic fibres are known for their endurance capabilities.

    False

    What is the term used to describe the recovery of oxygen in muscles after exercise?

    oxygen debt

    Slow oxidative fibres are also known as _____ ______ twitch fibres.

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

    Match the type of muscle fibre with its characteristic:

    <p>Slow oxidative fibres = Do not fatigue easily, main mode is aerobic respiration Fast oxidative-glycolytic fibres = Largest fibres, red color due to myoglobin Fast glycolytic fibres = Designed for quick, powerful movements Myoglobin = Protein that stores oxygen in muscle cells</p> Signup and view all the answers

    What type of muscular tissue contracts to move blood through the heart?

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

    Muscular tissue cannot generate heat during contraction.

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

    What is the scientific study of muscular tissue called?

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

    Muscular tissue is ________ and can produce electrical signals called muscle action potentials.

    <p>electrically excitable</p> Signup and view all the answers

    Which layer of fascia is most superficial?

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

    Match the type of muscular tissue with its primary function:

    <p>Skeletal muscle tissue = Movement of bones and stabilization of body positions Cardiac muscle tissue = Pumping blood through the heart Smooth muscle tissue = Regulating passage of substances through the body</p> Signup and view all the answers

    Muscles are surrounded by connective tissue layers called _________.

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

    What are muscle fibers also known as?

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

    What is the deepest layer of connective tissue that wraps individual muscle fibers?

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

    Skeletal muscles are innervated by autonomic motor neurons.

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

    What type of cells do muscle fibers start as during development?

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

    Muscle fibers are connected to _______ through tendons.

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

    Match the following muscle structures to their functions:

    <p>Myoglobin = Binds oxygen for muscle cells Myofibrils = Contractile units of muscle Sarcoplasmic reticulum = Stores calcium Tendons = Connect muscles to bones</p> Signup and view all the answers

    What structure is responsible for the striated appearance of skeletal muscles?

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

    Hypertrophy is the process by which muscle fibers can divide to increase mass.

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

    What type of protein is myosin classified as in muscle contraction?

    <p>motor protein</p> Signup and view all the answers

    The cytoplasm of myocytes is referred to as _______.

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

    What inhibits myosin-binding sites on thin filaments during muscle contraction?

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

    What happens to the Z-discs as myosin pulls on the thin filaments during muscle contraction?

    <p>They come together</p> Signup and view all the answers

    Each muscle fiber contains multiple nuclei.

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

    What is the name of the structure where two terminal cisternae meet a T-tubule?

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

    The thick and thin filaments change in length during muscle contraction.

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

    The thick filaments in a sarcomere are predominantly composed of _______.

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

    What molecules are required for muscle contraction?

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

    Match the following muscle bands/regions with their descriptions:

    <p>A-Band = Region of overlap of thick and thin filaments H-Zone = Only thick filaments I-Band = Only thin filaments M-Line = Center of the sarcomere</p> Signup and view all the answers

    Myosin binds and __________ ATP, causing a change in conformation.

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

    Match the following terms with their definitions:

    <p>Myosin = Thick filament that pulls on thin filaments Actin = Thin filament that slides during contraction Troponin = Complex that binds calcium Tropomyosin = Protein that blocks myosin-binding sites</p> Signup and view all the answers

    What is the role of tropomyosin in muscle contraction?

    <p>Blocks myosin-binding sites</p> Signup and view all the answers

    Depolarization of a muscle cell membrane results in a decrease in membrane potential.

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

    What structure releases calcium ions during muscle contraction?

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

    The __- bridge is formed when myosin binds to actin.

    <p>cross-bridge</p> Signup and view all the answers

    Which type of channels are responsible for repolarization?

    <p>Voltage-gated potassium channels</p> Signup and view all the answers

    Muscle contraction can occur even when ATP is absent in the muscle.

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

    What initiates the action potential in muscle fibers?

    <p>Signals from somatic motor neurons</p> Signup and view all the answers

    Calcium binds to ________ to facilitate muscle contraction.

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

    Match the following components with their functions in muscle contraction:

    <p>Acetylcholine = Neurotransmitter that activates muscle contraction Myosin = Pulls thin filaments during contraction Calcium ions = Cause conformational change in troponin ATP = Provides energy for myosin movement</p> Signup and view all the answers

    What is the term for the process that allows muscle fibers to contract in response to a nerve signal?

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

    Muscle tone requires all motor units to be active at the same time.

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

    What enzyme is responsible for breaking down acetylcholine at the neuromuscular junction?

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

    The ________ refractory ________ period occurs when a muscle fiber cannot respond to a new action potential.

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

    Match the following muscle contraction types with their descriptions:

    <p>Isotonic Contraction = Tension remains constant while the muscle changes length Isometric Contraction = Tension generated is not sufficient to cause movement Concentric Contraction = Muscle shortens while generating force Eccentric Contraction = Muscle lengthens while resisting a load</p> Signup and view all the answers

    During muscle contraction, which of the following happens to Ca2+?

    <p>It is released from the sarcoplasmic reticulum</p> Signup and view all the answers

    Aerobic respiration occurs when there is restricted access to oxygen.

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

    How does lactic acid production support ATP synthesis under low-oxygen conditions?

    <p>By regenerating NAD+ for glycolysis to continue.</p> Signup and view all the answers

    The primary muscle type involved in voluntary movements is _________ skeletal __________ muscle.

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

    What generally happens to muscle tension as the frequency of action potentials increases?

    <p>Tension increases</p> Signup and view all the answers

    A twitch contraction involves multiple action potentials in one motor unit.

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

    What is the average number of muscle fibers that a single motor neuron synapses with?

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

    In isotonic contraction, if the muscle shortens, it is called ________ concentric ________ contraction.

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

    Which of the following is a source of ATP for muscles?

    <p>Anaerobic glycolysis</p> Signup and view all the answers

    Calcium ATPases are responsible for what action in muscle cells?

    <p>Pumping calcium back into the sarcoplasmic reticulum</p> Signup and view all the answers

    Study Notes

    Muscle Tissue Types

    • Skeletal muscle tissue contracts to move bones and stabilize body positions.
    • Cardiac muscle tissue contracts to move blood through the heart.
    • Smooth muscle tissue contracts to regulate the passage of substances through the body, such as in the gastrointestinal tract and blood vessels.
    • All muscle tissue generates heat during contraction.

    Muscular Tissue Properties

    • Muscular tissue is electrically excitable. It produces electrical signals called muscle action potentials. Nerve tissues are also excitable.
    • Muscular tissue is contractile. Muscle action potentials stimulate contraction, which generates tension on bones and results in movement.
    • Muscular tissue is extensible. Tissue can be stretched without tearing, for example, smooth muscle around the stomach.
    • Muscular tissue is elastic. After stretching, the tissue returns to its resting length.

    Skeletal Muscle Structure

    • Skeletal muscle cells are called muscle fibers, which are elongated cells also known as myocytes. Muscle fibers contain bunched protein filaments called myofibrils.
    • A muscle (an organ) consists of muscle fibers, connective tissue, nerve and blood supply. Muscles are surrounded by connective tissue layers called fascia. Fascia physically groups muscles with similar functions and provides passage for nerves and vasculature.
    • Fascia is composed of three layers:
      • Epimysium: The most superficial layer. Dense irregular connective tissue that wraps muscles.
      • Perimysium: The intermediate layer. Dense irregular connective tissue that wraps fascicles, which are bundles of muscle fibers or cells.
      • Endomysium: The deepest layer. Mostly reticular fibers that wrap individual muscle fibers.

    Tendons and Aponeuroses

    • Fascia forms tendons, which are thick rope-like structures that connect muscles to bones.
    • Aponeuroses are a special type of tendon that form broad sheets. For example, the two bellies of the occipitofrontalis muscle are connected by the epicranial aponeurosis.

    Blood and Nerve Supply

    • Muscular tissue requires oxygen-rich blood for energy production.
    • Skeletal muscles are extensively innervated. Voluntary muscle contraction is regulated by somatic motor neurons. Axons branch from the spinal cord to muscles, with typically one branch per muscle fiber.

    Muscle Fiber Development

    • Humans are born with all the muscle fibers they will ever have.
    • Muscle fibers start as immature cells called myoblasts in the womb. These cells fuse as they mature, resulting in large, multinucleate cells.

    Muscle Fiber Structure

    • The plasma membrane of myocytes is called the sarcolemma.
    • The sarcolemma folds inward or invaginates to form T-tubules.
    • The cytoplasm of myocytes is called the sarcoplasm, which is densely packed with myofibrils and rich in glycogen (carbohydrate energy store).
    • The sarcoplasm also contains myoglobin, which is only found in muscle cells and binds oxygen at an iron-containing center called heme. Therefore, myocytes receive oxygen from inside and outside the cell.
    • The sarcoplasmic reticulum (SR) is the specialized smooth endoplasmic reticulum in muscle cells that stores and releases calcium.
    • The SR is extensively folded around each myofibril, with membrane folds called cisternae. The terminal cisternae specifically release Ca2+ to each T-tubule.
    • Where two terminal cisternae meet a T-tubule, it forms a triad.
    • Muscle fibers do not divide, but they can grow by laying down new protein and enlarging (hypertrophy).

    Hypertrophy

    • Hypertrophy is an increase in sarcoplasmic volume, which is a response to increased mechanical stress (e.g., weight-bearing exercise), hormones (e.g., anabolic steroids), or disease (e.g., increased demand on a diseased heart).

    Sarcomere Structure

    • Myofibrils are bundles of thread-like structures called myofilaments.
    • Each myofilament is made of contractile units called sarcomeres, which are joined end-to-end.
    • Each sarcomere consists of overlapping thick and thin filaments.
    • Thick filaments, made of myosin, extend from the midline (M-line) of the sarcomere.
    • Thin filaments, made of actin, extend from the ends (Z-discs) of the sarcomere.
    • The sarcomere is divided into zones and bands:
      • A band: The regions where thick and thin filaments overlap and everything in between.
      • H zone: The regions between the zones of overlap around the M-line, containing only thick filaments.
      • I band: The regions between zones of overlap around the Z-discs, containing only thin filaments.

    Muscle Contraction

    • Muscles generate force through contraction, involving three types of proteins:
      • Contractile proteins (shorten the sarcomere)
        • Myosin: A motor protein that converts chemical potential energy in ATP to mechanical energy. Each thick filament consists of approximately 300 myosin proteins. Myosin heads extend radially from ends of thick filaments, making contact with thin filaments and pulling them toward the M-line. Each myosin head has an ATP-binding site and an actin-binding site.
        • Actin: A cytoskeletal protein that forms long threads twisted around one another to form helical thin filaments. They have myosin-binding sites.
      • Regulatory proteins (control contraction)
        • Troponin: Binds Ca2+, causing it to move tropomyosin.
        • Tropomyosin: Blocks myosin-binding sites on thin filaments.
      • Structural proteins (stabilize and connect the sarcomere)
        • Titin: A large elastic protein that spans the M-line to Z-discs, stabilizing the position of thick filaments.
        • Dystrophin: Connects thin filaments to integral membrane proteins in the sarcolemma, reinforcing sarcomere structure and transmitting tension of sarcomeres to tendons.

    Sliding Filament Model

    • The sarcomere shortens as the thin filaments slide over the thick filaments, known as the sliding filament model.
    • The filaments themselves do not change length during the contraction cycle.

    The Contraction Cycle

    • The contraction cycle involves myosin binding to thin filaments, pulling them into the M-line, and then releasing them.
    • The steps of the contraction cycle are:
      • Myosin binds and hydrolyzes ATP, energizing myosin and changing its conformation (cocked, like a gun).
      • Myosin binds thin filaments to form a cross-bridge.
      • Myosin pulls the thin filaments toward the M-line; this conformational change is called the power stroke.
      • Myosin releases the thin filaments, requiring the binding of a new ATP molecule.
      • The cycle repeats.

    Calcium and Muscle Contraction

    • The myosin-binding sites on the thin filaments are initially obscured by tropomyosin until troponin binds Ca2+.
    • Ca2+ alters the conformation of troponin, moving tropomyosin off the myosin-binding sites on actin, allowing myosin to form a cross-bridge.
    • Muscle contraction requires both ATP and Ca2+.

    Sarcomere Structural Changes During Contraction

    • As myosin pulls on the thin filaments, the Z-discs come together, shortening the sarcomere.
    • The H zone disappears during contraction.
    • The I band narrows during contraction.

    Muscle Action Potentials

    • Muscle fibers are electrically excitable. Signals from somatic motor neurons stimulate an action potential.
    • The neuromuscular junction (NMJ) is where neurons and muscles meet.
    • Somatic motor neurons release neurotransmitters (e.g., acetylcholine), which bind to protein receptors on muscle cells and lead to an action potential in the muscle cell.

    Membrane Potential Changes during Action Potentials

    • The Na+-K+ pump maintains a negative resting membrane potential in cells, with the inside of the cell slightly more negative than the outside.
    • During an action potential, the membrane potential rapidly becomes positive, a process called depolarization.
    • The restoration of a negative membrane potential after depolarization is called repolarization.
    • The depolarization and repolarization stages are caused by voltage-gated ion channels. These channels open in response to changes in membrane potential, facilitating diffusion of ions down their concentration gradients.
    • Voltage-gated sodium (Na+) channels (VGNCs) allow Na+ ions to enter the cell, causing depolarization. These channels are only open when a change in membrane potential occurs. When acetylcholine binds, it opens some Na+ channels, leading to a slight depolarization.
    • Repolarization is achieved by voltage-gated K+ (potassium) channels (VGKCs), which are slower to open in response to membrane potential changes. Once open, K+ flows rapidly out of cells, restoring resting membrane potential. VGNCs close as the membrane repolarizes.

    Excitation-Contraction Coupling

    • The action potential travels along the sarcolemma to voltage-gated Ca2+ channels (VGCCs) at T-tubules. These VGCCs physically connect to Ca2+ release channels in the SR membrane.
    • Action potentials open VGCCs at triads, releasing and opening Ca2+ release channels of the SR.
    • Ca2+ spills into the sarcoplasm and binds troponin, moving tropomyosin off the myosin-binding sites on thin filaments, triggering muscle contraction.

    Muscle Relaxation

    • When the muscle action potential has passed, VGCCs in the sarcolemma close.
    • The SR Ca2+ release channels also close and reassociate with VGCCs at triads.
    • Ca2+-ATPases actively pump Ca2+ back into the SR and out of the cell.
    • The muscle can now relax. This entire process is called excitation-contraction coupling.

    Control of Muscle Tension

    • One action potential usually causes one contraction.
    • More frequent action potentials lead to more tension.
    • Each somatic motor neuron axon can form multiple NMJs with muscle fibers.
    • A motor unit is comprised of one somatic motor neuron and all the skeletal muscle fibers it synapses with (average of 150).
    • Larger muscles have many motor units distributed throughout the muscle.
    • All muscle fibers in a motor unit will contract and relax synchronously.
    • A twitch contraction is the contraction generated in all skeletal muscle fibers of one motor unit due to one action potential.
    • Twitch contractions proceed in three phases:
      • Latent period (2 msec): A delay between the stimulus (e.g., electrical stimulation) and muscle action. The action potential is moving through the sarcolemma, and Ca2+ is being released from the SR during this phase.
      • Contraction period (10-100 msec): Cross-bridges form, and sarcomeres shorten. Maximum tension develops during this phase.
      • Relaxation period (10-100 msec): Ca2+ is pumped back into the SR, myosin detaches from actin, and tension decreases during this phase.

    Refractory Period

    • While a muscle fiber is responding to an action potential, it temporarily becomes unresponsive to new signals. This short time period is called a refractory period.

    Muscle Tone

    • Not all motor units within a muscle are working simultaneously to prevent muscle fatigue and ensure smooth movements.
    • In large muscles, weaker motor units work first, and stronger motor units are recruited second.
    • Muscle tone refers to the small, involuntary contractions of alternating motor units that create slight muscle stiffness in postural muscles.

    Types of Muscle Contractions

    • Isotonic contractions maintain constant tension in the muscle as it changes length.
      • Concentric: These contractions occur when the muscle shortens to decrease the angle around a joint, like the biceps brachii contracting to pick up a book.
      • Eccentric: This contraction occurs when the muscle resists a load while lengthening, such as the biceps brachii lengthening as you slowly put a book down.
    • Isometric contractions occur when the generated tension is insufficient to overcome the resistance of the load, causing the bones not to move (e.g., holding a book out or holding a plank).
    • Isometric contractions function to stabilize many joints during movement.

    Muscle Metabolism

    • Muscle cells require ATP not only for the contraction cycle but also for other cellular processes, such as maintaining the sodium-potassium pump and transporting calcium back into the sarcoplasmic reticulum.
    • Muscles generate ATP using three methods:
      • Consuming creatine phosphate: At rest, unused ATP is dephosphorylated to make creatine phosphate. During activity, muscles rapidly dephosphorylate creatine phosphate to regenerate ATP. Both phosphate transfers are catalyzed by creatine kinase. This process is quick but provides only a small amount of ATP.
      • Aerobic respiration: Muscles can release glucose monomers from glycogen stores or uptake glucose from blood. Glucose is broken into two three-carbon molecules called pyruvate in ten chemical reactions. This process of splitting glucose is called glycolysis.
      • Anaerobic glycolysis: If muscles have restricted access to oxygen, they cannot respire the products of glycolysis. Pyruvate is fermented into lactic acid.

    Muscle Oxygen Debt

    • Muscles require oxygen after exercise to replenish myoglobin, convert lactic acid back to glucose in the liver, and replenish creatine phosphate.
    • This demand for oxygen after exercise is referred to as "oxygen debt."

    Muscle Fiber Types

    • There are three main types of skeletal muscle fibers: slow oxidative, fast oxidative-glycolytic, and fast glycolytic.
    • These fiber types differ in structure, function, and appearance.

    Slow Oxidative Fibers

    • Slow oxidative fibers appear dark red due to their high myoglobin and capillary density.
    • They are known as "slow twitch" fibers due to their longer contraction cycle (100-200 milliseconds).
    • Their primary metabolic mode is aerobic respiration, which allows them to resist fatigue during endurance activities and postural muscle function.

    Fast Oxidative-Glycolytic Fibers

    • Fast oxidative-glycolytic fibers are also dark red with high myoglobin and capillary density.
    • They have the largest fiber size.
    • These fibers exhibit faster contraction cycles due to their glycolytic capacity, but their oxidative capabilities also allow them to contribute to endurance activities.

    Fast Glycolytic Fibers

    • Fast glycolytic fibers are white in appearance because of their lower myoglobin content.
    • They are the fastest contracting fiber type, making them important for short bursts of high-intensity activity.
    • They primarily use anaerobic glycolysis for energy production which makes them susceptible to fatigue.

    Studying That Suits You

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

    Quiz Team

    Description

    Test your knowledge on muscle tissue, its types, and functions. This quiz covers key concepts related to muscle fibers, their recovery, and the scientific study of muscular tissue. Perfect for students studying exercise science or anatomy.

    More Like This

    Use Quizgecko on...
    Browser
    Open
    Browser
    Browser