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Questions and Answers
What is the role of acetylcholine (ACh) in muscle contraction?
What is the role of acetylcholine (ACh) in muscle contraction?
Which of the following best describes a motor unit?
Which of the following best describes a motor unit?
What occurs during the latent period of a muscle twitch?
What occurs during the latent period of a muscle twitch?
Which phase of a muscle twitch involves the breaking of cross-bridges?
Which phase of a muscle twitch involves the breaking of cross-bridges?
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How do motor units responsible for strength differ from those allowing fine control?
How do motor units responsible for strength differ from those allowing fine control?
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What type of muscle tissue is characterized by being involuntary and non-striated?
What type of muscle tissue is characterized by being involuntary and non-striated?
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Which muscle type has fibers that are striated, branched, and allows contractions to spread through the heart wall?
Which muscle type has fibers that are striated, branched, and allows contractions to spread through the heart wall?
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What is the main function of skeletal muscles in the body?
What is the main function of skeletal muscles in the body?
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What connects the skeletal muscle to the bone?
What connects the skeletal muscle to the bone?
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During muscle contraction, which structure is responsible for pulling on the tendons?
During muscle contraction, which structure is responsible for pulling on the tendons?
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Which type of muscle contracts voluntarily?
Which type of muscle contracts voluntarily?
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What structure helps to cushion and lubricate tendons and bones?
What structure helps to cushion and lubricate tendons and bones?
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What is the primary action of cardiac muscle?
What is the primary action of cardiac muscle?
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What arrangement do smooth muscle fibers have?
What arrangement do smooth muscle fibers have?
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Which statement about skeletal muscles is true?
Which statement about skeletal muscles is true?
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What is the primary function of myoglobin in muscle fibers?
What is the primary function of myoglobin in muscle fibers?
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What structure forms extensions of the sarcolemma into the muscle fiber?
What structure forms extensions of the sarcolemma into the muscle fiber?
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Which component of the muscle fiber stores calcium ions?
Which component of the muscle fiber stores calcium ions?
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What do myofibrils consist of?
What do myofibrils consist of?
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What does the Z line in a sarcomere represent?
What does the Z line in a sarcomere represent?
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What are the two types of myofilaments that make up a sarcomere?
What are the two types of myofilaments that make up a sarcomere?
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Which best describes the A band in a sarcomere?
Which best describes the A band in a sarcomere?
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How are thick myofilaments characterized in structure?
How are thick myofilaments characterized in structure?
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What occurs when a muscle fiber contracts according to the Sliding Filament Theory?
What occurs when a muscle fiber contracts according to the Sliding Filament Theory?
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Which role does ATP play in muscle contraction?
Which role does ATP play in muscle contraction?
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What is the function of troponin in muscle contraction?
What is the function of troponin in muscle contraction?
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Where does the release of acetylcholine (ACh) occur during muscle contraction?
Where does the release of acetylcholine (ACh) occur during muscle contraction?
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What happens to the H band during muscle contraction?
What happens to the H band during muscle contraction?
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Which of the following describes the power stroke during muscle contraction?
Which of the following describes the power stroke during muscle contraction?
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How does a motor neuron stimulate muscle fibers?
How does a motor neuron stimulate muscle fibers?
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What maintains the continuous cycle of muscle contraction?
What maintains the continuous cycle of muscle contraction?
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What is rigor mortis, and why does it occur?
What is rigor mortis, and why does it occur?
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What is the role of an agonist muscle?
What is the role of an agonist muscle?
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Which muscle group acts as antagonists to each other?
Which muscle group acts as antagonists to each other?
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Which term indicates the size of the muscle?
Which term indicates the size of the muscle?
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What is the action of the masseter muscle?
What is the action of the masseter muscle?
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What describes the shape of the trapezius muscle?
What describes the shape of the trapezius muscle?
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What is the primary action of the quadriceps femoris muscle?
What is the primary action of the quadriceps femoris muscle?
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What does the term 'flexor' indicate in muscle action?
What does the term 'flexor' indicate in muscle action?
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Which protein binds oxygen in muscle fibers?
Which protein binds oxygen in muscle fibers?
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What are myofibrils made of?
What are myofibrils made of?
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What is the role of the sarcoplasmic reticulum?
What is the role of the sarcoplasmic reticulum?
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Which muscle primarily raises and laterally rotates the thigh?
Which muscle primarily raises and laterally rotates the thigh?
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Which action is performed by the extensor digitorum?
Which action is performed by the extensor digitorum?
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Which muscle is responsible for extending the thigh back?
Which muscle is responsible for extending the thigh back?
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What is the significance of striations in muscle fibers?
What is the significance of striations in muscle fibers?
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What causes muscle fatigue during prolonged contraction?
What causes muscle fatigue during prolonged contraction?
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Which pathway provides the fastest ATP production for muscles?
Which pathway provides the fastest ATP production for muscles?
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What characterizes fast-twitch muscle fibers?
What characterizes fast-twitch muscle fibers?
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What happens during muscle recruitment?
What happens during muscle recruitment?
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What is the primary energy source used in cellular respiration?
What is the primary energy source used in cellular respiration?
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What physiological phenomenon occurs when a muscle relaxes despite continued stimulation?
What physiological phenomenon occurs when a muscle relaxes despite continued stimulation?
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What is a common cause of myositis?
What is a common cause of myositis?
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Which type of muscle fiber is primarily used in endurance sports?
Which type of muscle fiber is primarily used in endurance sports?
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What can cause the buildup of lactate in muscles?
What can cause the buildup of lactate in muscles?
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What is a characteristic of muscular dystrophy?
What is a characteristic of muscular dystrophy?
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Which muscle condition involves twisting of a joint with swelling?
Which muscle condition involves twisting of a joint with swelling?
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In which condition do facial spasms occur that can be controlled with effort?
In which condition do facial spasms occur that can be controlled with effort?
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What is the role of myoglobin in muscle cells?
What is the role of myoglobin in muscle cells?
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Which of the following is NOT a characteristic of fast-twitch fibers?
Which of the following is NOT a characteristic of fast-twitch fibers?
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Study Notes
The Muscular System
- The muscular system is responsible for movement in the entire organism and the movement of materials, e.g., blood, food, within the body.
- Three types of muscle tissue exist: smooth, cardiac, and skeletal.
- Muscle cells are also known as muscle fibers.
Smooth Muscle
- Smooth muscle fibers are tapered cylinders with a single nucleus.
- They are arranged in parallel lines, forming sheets.
- Smooth muscle is found in the walls of hollow internal organs and blood vessels, causing those walls to contract.
- The contraction of smooth muscle is involuntary.
- Smooth muscle can sustain prolonged contractions and does not fatigue easily.
Cardiac Muscle
- Cardiac muscle forms the heart wall.
- Cardiac muscle fibers are branched, striated, and tubular, with a single nucleus.
- They interlock at intercalated discs, containing gap junctions that permit contractions to spread throughout the heart wall.
- Cardiac muscle relaxes completely between contractions, preventing fatigue.
- Cardiac muscle contracts rhythmically without nervous stimulation; the contraction is involuntary.
Skeletal Muscle
- Skeletal muscle fibers are tubular, multinucleated, and striated.
- They make up skeletal muscles attached to the skeleton.
- This type of muscle fiber is very long, running the entire length of the muscle.
- Skeletal muscles are voluntarily controlled.
- Skeletal muscles function in groups.
Skeletal Muscle Structure
- Fascicle: A bundle of skeletal muscle fibers.
- Fascia: Connective tissue covering muscles, extending to form tendons.
- Bursae: Small, fluid-filled sacs between tendons and bones, acting as cushions and lubrication.
- Origin: The attachment site of a muscle to a stationary bone.
- Insertion: The attachment site of a muscle to a bone that moves during contraction.
- Groups of Muscles: Muscles function in groups, agonist, synergist, and antagonist. - Agonist: The primary mover doing most of the work. - Synergist: Assists the agonist. - Antagonist: Acts opposite to the prime mover.
Names and Actions of Skeletal Muscles
- Muscle names often show size (e.g., gluteus maximus, gluteus minimus), form (e.g., deltoid, trapezius), or location (e.g., external obliques, internal obliques).
- Other terms describe direction of muscle fibers (e.g., rectus abdominis), attachment sites (e.g., sternocleidomastoid), and numbers of attachments.
Components of Muscle Fibers
- Sarcolemma: Plasma membrane of a muscle fiber; forms T tubules.
- Sarcoplasm: Cytoplasm of a muscle fiber; contains organelles, including myofibrils.
- Myoglobin: Red pigment storing oxygen for muscle contraction.
- T tubules: Extension of sarcolemma; conveys impulses that cause calcium release.
- Sarcoplasmic reticulum: Smooth endoplasmic reticulum of a muscle fiber; stores calcium.
- Myofibril: A bundle of myofilaments that contracts.
- Myofilaments: Actin or myosin filaments.
- Sarcomeres: Contractile units within a myofibril.
- Two Types of Myofilaments: Thick (myosin) and Thin (actin). - Thick (myosin) myofilaments: Shaped like golf clubs, ending in cross-bridges. - Thin (actin) myofilaments: Composed of two intertwined strands of actin.
- Bands within a Sarcomere: I band (thin filaments only), A band (overlapping thin and thick filaments), H band (thick filaments only). Z line/discs is found at the end of every sarcomere and at the edge of each myofilament
The Sliding Filament Theory
- As the muscle fiber contracts, the sarcomeres shorten.
- Myofilaments slide past each other; their length remains the same.
- I band shortens and the Z lines move inward, alongside an almost disappearing H band.
- ATP provides energy for myosin heads to bind to actin, break down the ATP, and pull actin filaments toward the center of the sarcomere.
- Rigor mortis: the muscle stays contracted at death because ATP is needed to break cross-bridges.
Muscle Fiber Contraction.
- Motor neuron: A nerve cell stimulating muscle fibers to contract.
- Nerve: Group of axons.
- Axon: Long extension of a neuron that stimulates a muscle fiber.
- Neuromuscular junction: Where axon terminals form a synapse with the sarcolemma, transmitting signals.
- Synaptic cleft: The space separating the axon terminal and the sarcolemma.
- Acetylcholine (ACh): neurotransmitter released at the neuromuscular junction.
Motor Units and Muscle Twitch
- Motor unit: A motor neuron and all the muscle fibers it innervates.
- Muscle twitch: A single contraction of a muscle fiber lasting a fraction of a second.
- Stages of Muscle Twitch: Latent period, contraction period and relaxation period.
- Summation of Muscle Twitch: Increased muscle contraction due to increased calcium.
- Tetanus: A maximal sustained contraction.
- Fatigue: Muscle relaxes even when stimulation continues, often due to depletion of energy reserves.
Energy for Muscle Contraction
- Creatine phosphate (CP) pathway: Simplest and fastest way to produce ATP during exercise.
- Fermentation: Anaerobic process that produces ATP from glycogen.
- Cellular respiration: Aerobic process in mitochondria, most efficient way to produce ATP.
Fast-twitch and Slow-twitch Fibers
- Fast-twitch fibers (white): Designed for strength and explosions of energy, not endurance; primarily anaerobic.
- Slow-twitch fibers (red): Endurance sports; primarily aerobic.
Common Muscular Conditions
- Spasms: Sudden involuntary muscle contractions.
- Cramps: Strong painful muscle spasms.
- Convulsion: Multiple spasms.
- Strain: Stretching or tearing of a muscle.
- Sprain: Twisting of a joint, typically injuring muscles, ligaments, tendons, and blood vessels.
- Tendinitis: Inflammation of a tendon.
Muscular Diseases
- Myalgia: Achy muscles, often due to overuse.
- Myositis: Inflammation of muscles, commonly caused by infection or immune disorders.
- Fibromyalgia: Chronic condition with widespread pain, tenderness, and stiffness in muscles.
- Sarcomas: Cancers originating in muscle or connective tissues surrounding muscles; can also occur in bone, adipose, and cartilage.
- Muscular Dystrophy: Progressive degeneration and weakening of muscles due to genetic defects.
- Myasthenia gravis: Autoimmune disease weakening muscles of the eyelids, face, neck, and extremities; typically caused by immune system attacking acetylcholine receptors.
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Description
Test your knowledge on the muscular system, including the different types of muscle tissue such as smooth, cardiac, and skeletal muscles. Learn about their functions, characteristics, and how they contribute to movement within the body. This quiz is perfect for students studying human anatomy.
