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Questions and Answers
What is the primary function of tendons in the musculoskeletal system?
What is the primary function of tendons in the musculoskeletal system?
What component accounts for the alternating dark and light bands seen in a myofibril?
What component accounts for the alternating dark and light bands seen in a myofibril?
Which structure represents the functional unit of a muscle?
Which structure represents the functional unit of a muscle?
What is contained within the H-zone of a myofibril?
What is contained within the H-zone of a myofibril?
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What distinguishes the I-band in a myofibril?
What distinguishes the I-band in a myofibril?
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Which muscle type is characterized by striations and strong, short contractions?
Which muscle type is characterized by striations and strong, short contractions?
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What is the primary function of smooth muscle?
What is the primary function of smooth muscle?
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What is the role of cardiac muscle in the body?
What is the role of cardiac muscle in the body?
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Which tissue type comprises the majority of body weight?
Which tissue type comprises the majority of body weight?
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What distinguishes striated muscle from unstriated muscle?
What distinguishes striated muscle from unstriated muscle?
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What characteristic is common to skeletal muscle fibers?
What characteristic is common to skeletal muscle fibers?
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How does muscle tissue primarily convert energy?
How does muscle tissue primarily convert energy?
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Which of the following muscle types is classified as involuntary?
Which of the following muscle types is classified as involuntary?
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What is the primary role of myoglobin in muscle cells?
What is the primary role of myoglobin in muscle cells?
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Which structure separates individual muscle cells within a fascicle?
Which structure separates individual muscle cells within a fascicle?
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What neurotransmitter is released at the myoneural junction to stimulate muscle contraction?
What neurotransmitter is released at the myoneural junction to stimulate muscle contraction?
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Which of the following best describes the composition of skeletal muscle in terms of protein content?
Which of the following best describes the composition of skeletal muscle in terms of protein content?
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What is the function of lactic acid in muscle cells?
What is the function of lactic acid in muscle cells?
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What is the typical innervation ratio for motor neurons to muscle fibers in eye muscles?
What is the typical innervation ratio for motor neurons to muscle fibers in eye muscles?
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Which layer of connective tissue surrounds large bundles of muscle?
Which layer of connective tissue surrounds large bundles of muscle?
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What is the structural unit of contraction within muscle fibers?
What is the structural unit of contraction within muscle fibers?
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Which of the following statements about myosin is true?
Which of the following statements about myosin is true?
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What is the main characteristic of skeletal muscle?
What is the main characteristic of skeletal muscle?
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Which type of muscle is primarily responsible for strong, continuous contractions?
Which type of muscle is primarily responsible for strong, continuous contractions?
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Which statement correctly describes tendons?
Which statement correctly describes tendons?
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What distinguishes cardiac muscle from skeletal muscle?
What distinguishes cardiac muscle from skeletal muscle?
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What is the primary role of myosin-binding proteins in the sarcomere?
What is the primary role of myosin-binding proteins in the sarcomere?
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Which component is part of the thin filament structure?
Which component is part of the thin filament structure?
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In a contracted sarcomere, how does the H zone change?
In a contracted sarcomere, how does the H zone change?
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What is the molecular weight of G-actin?
What is the molecular weight of G-actin?
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What is the primary function of tropomyosin in muscle contraction?
What is the primary function of tropomyosin in muscle contraction?
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Which protein is known to provide elasticity to the sarcomere?
Which protein is known to provide elasticity to the sarcomere?
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What does the A band in the sarcomere represent?
What does the A band in the sarcomere represent?
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What is the diameter range of thin filaments?
What is the diameter range of thin filaments?
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What type of muscle has branching fibers and central nuclei?
What type of muscle has branching fibers and central nuclei?
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Which type of muscle contraction is characterized as being stronger and continuous?
Which type of muscle contraction is characterized as being stronger and continuous?
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What structure is primarily responsible for coordinating the contraction of cardiac muscle tissue?
What structure is primarily responsible for coordinating the contraction of cardiac muscle tissue?
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Which characteristic is NOT associated with smooth muscle?
Which characteristic is NOT associated with smooth muscle?
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In cardiac muscle cells, what are the structures that bind cells together called?
In cardiac muscle cells, what are the structures that bind cells together called?
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Study Notes
Muscle Tissue Structure
- Muscle tissue is a type of excitable tissue.
- Muscle tissue makes up a large portion of the body, approximately 50%.
- Muscle tissue has three main types: skeletal, cardiac, and smooth.
- Skeletal muscle is responsible for movement of the body and manipulation of objects.
- Cardiac muscle powers the heart's pumping action.
- Smooth muscle moves substances through hollow internal organs.
Four Tissue Types
- Epithelial tissue lines and protects surfaces, including skin and mucous membranes.
- Muscle tissue is responsible for movement. Types include skeletal, smooth, and cardiac muscles.
- Nervous tissue is involved in communication and control, comprising the brain and spinal cord.
- Connective tissue supports other tissues, including loose connective tissue (e.g., ligaments, tendons) and dense connective tissue (e.g., bone, cartilage, and blood).
Muscle Structure
- Skeletal muscle cells are also called muscle fibers. They're long and cylindrical, and contain multiple nuclei.
- Muscle fibers are made up of myofibrils.
- Myofibrils are composed of myofilaments.
- Myofilaments, primarily actin and myosin, are responsible for muscle contraction.
- Muscle cells are organized into fascicles, then bundles of fascicles form a muscle.
- Tendons connect muscles to bones while aponeuroses attach to bones, cartilages, or other connective tissues.
- Structure includes sarcolemma (outer membrane), sarcoplasm (cytoplasm), and sarcoplasmic reticulum (specialized smooth ER important for calcium ion storage).
Skeletal Muscle Cells
- A motor unit is comprised of a single motor neuron that innervates the entire muscle fiber.
- Myoneural junction is the synapse between the motor neuron and muscle fiber.
- Acetylcholine is the neurotransmitter released at the myoneural junction for muscle contraction.
- Motor end plate is the specialized area of the sarcolemma under the axon terminal.
- The innervation ratio varies depending on the muscle, from 1:100 to 1:2000.
Basic Units of Muscle Organisation
- Sarcolemma is the plasma membrane, which has a well-developed basement membrane outside.
- Sarcoplasm is the cytoplasm excluding the myofibrils.
- Sarcoplasmic Reticulum is the smooth endoplasmic reticulum found within the muscle cell.
- Epimysium is a thick connective tissue layer surrounding a bundle of fascicles.
- Perimysium is the connective tissue wrapping each fascicle.
- Endomysium is a thin connective tissue layer encasing individual muscle fibers.
- Fascicle is a bundle of muscle cells encased by perimysium.
- Skeletal muscles are connected to bones via tendons.
Skeletal Muscle - Myofibrils
- Myofibrils are made up of sarcomeres, repeating units arranged end-to-end.
- Each sarcomere gives the skeletal muscle its striated appearance.
- Sarcomeres contain myofilaments.
- Myofilaments are actin and myosin filaments, which interact for contraction.
Myofilament Components
- Components include Z-discs, A band, I band, H zone, and M line.
- Z-discs are dense membranes separating sarcomeres.
- A band contains thick myosin filaments (sometimes overlapped by thin actin).
- I band contains thin actin filaments.
- H zone is the center part of A band, mainly containing thick filaments.
- M line supports the thick filaments in the center of sarcomere.
- Myofilaments include thick myosin and thin actin filaments.
Myofilaments (Actin and Myosin)
- Actin is a thin filament protein that plays a key role in muscle contraction.
- Thin filaments consist of 3 proteins: actin, tropomyosin, and troponin.
- Myosin is a thick filament protein that binds to actin during contraction.
- Muscle contraction involves binding myosin to actin with the use of ATP, leading to shortening of the sarcomeres.
Regulatory Proteins
- Regulatory proteins include Tropomyosin and Troponin.
- Troponin is a complex of 3 proteins: TnC (Ca2+ binding), TnI (inhibitory), and TnT (tropomyosin binding).
- Under resting conditions, tropomyosin covers the myosin-binding sites on actin, preventing contraction. Calcium ion release causes tropomyosin to move, allowing myosin to bind to actin.
- Tropomyosin binds to actin and prevents the binding of myosin to actin.
Thin Filaments
- Thin filaments have a length of about 1 µm and a diameter of 5-8 nm.
- Nebulin and Titin are elasticity-related proteins within thin filaments and are important during contraction.
Thick Filaments
- Thick filaments are made up of myosin protein molecules. Myosin has a head and a tail region.
- The heads bind to actin molecules to initiate cross-bridge formation during muscle contraction.
Cardiac Muscle
- Structure includes intercalated discs which are specific for cardiac muscle.
- Cardiac muscle cells are also called cardiocytes.
- Cardiocytes are branched muscle cells and are connected via gap junctions.
- Cardiac muscle is under involuntary control and responsible for the rhythmic contractions of the heart.
Smooth Muscle
- Smooth muscle cells are spindle-shaped with a single nucleus.
- Smooth muscle cells are typically located in walls of hollow organs, such as blood vessels, intestines, and the digestive system.
- Smooth muscle is under involuntary control.
- Smooth muscle contraction is often slow and sustained. - Smooth muscles exist in two main types, multi-unit and single-unit. They differ in their innervation(how they receive signaling) and their response to stimuli.
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Description
Test your knowledge on the anatomy and functions of muscle tissue with this engaging quiz. Explore concepts related to tendons, myofibrils, and various muscle types, including striated, smooth, and cardiac muscles. Perfect for students studying human biology or anatomy.
