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Questions and Answers
What is the primary function of myofibrils in muscle fibers?
What is the primary function of myofibrils in muscle fibers?
The I-band is formed exclusively of myosin filaments.
The I-band is formed exclusively of myosin filaments.
False (B)
What type of protein is myoglobin and what is its function?
What type of protein is myoglobin and what is its function?
Myoglobin is an oxygen-binding pigmented protein that provides oxygen for oxidative reactions.
The __________ is a well-developed smooth endoplasmic reticulum in muscle cells that stores calcium ions.
The __________ is a well-developed smooth endoplasmic reticulum in muscle cells that stores calcium ions.
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Match the muscle components with their descriptions:
Match the muscle components with their descriptions:
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Which organelle is primarily responsible for energy production in muscle cells?
Which organelle is primarily responsible for energy production in muscle cells?
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The H-zone is a pale area located in the middle of the I-band.
The H-zone is a pale area located in the middle of the I-band.
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Name one of the large proteins that link thick myofilaments to the Z-line.
Name one of the large proteins that link thick myofilaments to the Z-line.
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Which type of skeletal muscle fiber is characterized by a rich supply of myoglobin?
Which type of skeletal muscle fiber is characterized by a rich supply of myoglobin?
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White muscle fibers are rich in mitochondria and have low levels of glycogen.
White muscle fibers are rich in mitochondria and have low levels of glycogen.
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What primarily composes the A-band in muscle fibers?
What primarily composes the A-band in muscle fibers?
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What is the primary source of energy for red skeletal muscle fibers?
What is the primary source of energy for red skeletal muscle fibers?
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The I-band becomes shorter during muscle contraction.
The I-band becomes shorter during muscle contraction.
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Skeletal muscle hypertrophy occurs through the enlargement of muscle fibers due to __________.
Skeletal muscle hypertrophy occurs through the enlargement of muscle fibers due to __________.
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Match the following types of muscle fibers with their characteristics:
Match the following types of muscle fibers with their characteristics:
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What is the functional unit of contraction in muscle fibers?
What is the functional unit of contraction in muscle fibers?
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The __________ are invaginations of the sarcolemma that encircle myofibrils.
The __________ are invaginations of the sarcolemma that encircle myofibrils.
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What happens to satellite cells after muscle injury?
What happens to satellite cells after muscle injury?
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What happens to calcium levels when depolarization stops?
What happens to calcium levels when depolarization stops?
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Muscular dystrophy is a condition characterized by an increase in muscle function.
Muscular dystrophy is a condition characterized by an increase in muscle function.
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What is the musculotendinous junction?
What is the musculotendinous junction?
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Match the skeletal muscle types with their characteristics:
Match the skeletal muscle types with their characteristics:
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The H-zone contains both actin and myosin filaments.
The H-zone contains both actin and myosin filaments.
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When the muscle contracts, the A-band __________ in length.
When the muscle contracts, the A-band __________ in length.
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What primarily causes muscle cramps?
What primarily causes muscle cramps?
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Myasthenia Gravis affects the skeletal muscles by enhancing muscle strength.
Myasthenia Gravis affects the skeletal muscles by enhancing muscle strength.
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What is the primary function of the cardiac muscle?
What is the primary function of the cardiac muscle?
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Cardiac muscle fibers are characterized by a cylindrical shape and have a nucleus that is _____ and _____ in each cardiac myocyte.
Cardiac muscle fibers are characterized by a cylindrical shape and have a nucleus that is _____ and _____ in each cardiac myocyte.
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Match the following terms related to cardiac muscle with their descriptions:
Match the following terms related to cardiac muscle with their descriptions:
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Which component is NOT present in the sarcoplasm of cardiac muscle fibers?
Which component is NOT present in the sarcoplasm of cardiac muscle fibers?
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The myocardium forms the outer layer of the heart.
The myocardium forms the outer layer of the heart.
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What changes occur in cardiac myocytes with age?
What changes occur in cardiac myocytes with age?
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What structural components are found in the transverse regions of the cardiac muscle intercalated discs?
What structural components are found in the transverse regions of the cardiac muscle intercalated discs?
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Cardiac muscle fibers can regenerate after injury.
Cardiac muscle fibers can regenerate after injury.
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What is the primary function of Purkinje muscle fibers?
What is the primary function of Purkinje muscle fibers?
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The cardiac muscle's involuntary contraction is modulated, but not initiated, by ______ innervations.
The cardiac muscle's involuntary contraction is modulated, but not initiated, by ______ innervations.
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Match the following structures with their functions:
Match the following structures with their functions:
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What occurs during a myocardial infarction?
What occurs during a myocardial infarction?
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Angina is characterized by severe chest pain resulting from increased oxygenation of the heart muscle.
Angina is characterized by severe chest pain resulting from increased oxygenation of the heart muscle.
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What type of epithelium covers the heart valves?
What type of epithelium covers the heart valves?
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What is the primary function of smooth muscles?
What is the primary function of smooth muscles?
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Smooth muscle fibers have a striated appearance.
Smooth muscle fibers have a striated appearance.
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What hormone is a potent stimulator of smooth muscle contraction?
What hormone is a potent stimulator of smooth muscle contraction?
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Smooth muscle cells may be affected by hormones such as __________.
Smooth muscle cells may be affected by hormones such as __________.
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Where are smooth muscles primarily located?
Where are smooth muscles primarily located?
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Match the following characteristics with their corresponding smooth muscle features:
Match the following characteristics with their corresponding smooth muscle features:
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Smooth muscle fibers are arranged in sheets, layers, or bundles.
Smooth muscle fibers are arranged in sheets, layers, or bundles.
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What type of connective tissue surrounds each bundle of smooth muscle fibers?
What type of connective tissue surrounds each bundle of smooth muscle fibers?
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Flashcards
Sarcoplasmic Reticulum
Sarcoplasmic Reticulum
A network of smooth endoplasmic reticulum surrounding myofibrils in muscle cells. It plays a crucial role in storing and releasing calcium ions (Ca++) for muscle contraction.
Myofibrils
Myofibrils
Cylindrical protein structures that make up muscle fibers. They are responsible for muscle contraction and are arranged in parallel bundles within each muscle cell.
Sarcomere
Sarcomere
The functional unit of a myofibril, responsible for muscle contraction. It is characterized by alternating dark (A) and light (I) bands.
A-band
A-band
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I-band
I-band
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Z-line
Z-line
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H-zone
H-zone
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M-line
M-line
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What are the characteristics of red muscle fibers?
What are the characteristics of red muscle fibers?
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What are the characteristics of white muscle fibers?
What are the characteristics of white muscle fibers?
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What are intermediate fibers?
What are intermediate fibers?
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What are satellite cells and their function?
What are satellite cells and their function?
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What is the musculotendinous junction?
What is the musculotendinous junction?
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What is skeletal muscle hypertrophy?
What is skeletal muscle hypertrophy?
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What is muscular dystrophy?
What is muscular dystrophy?
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T-tubules (Transverse tubules)
T-tubules (Transverse tubules)
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Muscle Contraction (Role of the Tubular System)
Muscle Contraction (Role of the Tubular System)
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Muscle Relaxation
Muscle Relaxation
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Muscle Cramps
Muscle Cramps
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Myasthenia Gravis
Myasthenia Gravis
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Cardiac Muscle
Cardiac Muscle
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Epicardium
Epicardium
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Endocardium
Endocardium
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Cardiac Muscle Fibers
Cardiac Muscle Fibers
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Intercalated Discs
Intercalated Discs
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Cardiac Myocyte Nucleus
Cardiac Myocyte Nucleus
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Purkinje muscle fibers
Purkinje muscle fibers
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Myocardial infarction
Myocardial infarction
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Gap junctions
Gap junctions
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Cardiac muscle contraction
Cardiac muscle contraction
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Angina
Angina
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Reduced oxygenation of ventricular muscle
Reduced oxygenation of ventricular muscle
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What is smooth muscle?
What is smooth muscle?
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How are smooth muscle fibers connected?
How are smooth muscle fibers connected?
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What is the endomysium?
What is the endomysium?
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How are smooth muscle fibers arranged?
How are smooth muscle fibers arranged?
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How does oxytocin affect smooth muscle?
How does oxytocin affect smooth muscle?
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What are caveolae and how do they affect smooth muscle contraction?
What are caveolae and how do they affect smooth muscle contraction?
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What is the shape of smooth muscle fibers?
What is the shape of smooth muscle fibers?
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What are dense bodies in smooth muscle?
What are dense bodies in smooth muscle?
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Study Notes
Muscular Tissue
- The structural and functional unit is a specialized elongated cell called a muscle fiber containing contractile filaments (actin and myosin).
- The cell membrane of muscle fibers is called the sarcolemma, and the cytoplasm is called the sarcoplasm.
- Sarcoplasmic reticulum is the smooth ER.
- Sarcoplasm is acidophilic and contains organelles like mitochondria, sarcoplasmic reticulum, and myofibrils, and inclusions like glycogen, myoglobin, and fat.
- Muscle tissue originates from the Mesoderm.
- Muscle cells (myocytes) can form all types of muscle tissue.
Types of Muscular Tissue
- Classified according to the shape and function of their cells:
- Skeletal muscle
- Cardiac muscle
- Smooth muscle
Skeletal Muscle
- Attached to the skeleton.
- Consists of muscle fibers held and supported by connective tissue:
- Epimysium: surrounds the whole muscle.
- Perimysium: surrounds bundles (fascicles) of muscle fibers.
- Endomysium: surrounds each individual muscle fiber; a layer of reticular fibers containing small blood vessels and nerves.
- Connective tissue is essential for force transmission and nourishment of the muscle fibers through diffusion.
Skeletal Muscle Fiber
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Cylindrical, non-branched (except in face and tongue).
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Size: 10-100 µm in diameter and markedly variable in length.
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Multiple, oval nuclei just under the sarcolemma.
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Sarcoplasm is acidophilic with uniform transverse striations in longitudinal section.
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Organelles:
- Myofibrils: numerous cylindrical, parallel, longitudinal fibrils extending the entire muscle fiber.
- Sarcoplasmic reticulum: a well-developed smooth endoplasmic reticulum forming networks around myofibrils. Essential for calcium storage and release during muscle contraction.
- Mitochondria: numerous, arranged in rows between myofibrils.
- Other organelles: few, found mainly in the perinuclear cytoplasm.
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Inclusions:
- Myoglobin: oxygen-binding protein.
- Glycogen granules: energy storage.
- Lipid droplets.
Myofibrils
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The myofibrils are composed of two main types of protein filaments:
- Thin filaments (actin filaments).
- Thick filaments (myosin filaments).
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Thick filaments are located in the A-band, while the Thin filaments extend into and occupy the I band, and both are connected to the Z lines.
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Dark bands (A-bands) and light bands (I-bands).
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The A-band appears dark because it contains both actin and myosin filaments, and the I band is light because it contains only actin filaments.
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The H zone is a pale area in the middle of the A-band, which contains only myosin filaments.
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The M-line bisects the H zone.
Triad Tubular System (T-system)
- Formed of three tubules: one T-tubule (transverse tubule) in the middle, and two wide terminal cisternae of sarcoplasmic reticulum.
- The T-tubules are invaginations of the sarcolemma.
- The lumen of the T-tubule is continuous with the extracellular space.
- Located at the junction between the A and I bands.
Function of Skeletal Muscle
- Skeletal muscle is voluntary.
- Skeletal muscle's contraction is transmitted to the T tubules, then to the depth of the fiber and stimulate the sarcoplasmic reticulum to release calcium (Ca²⁺), which facilitates the sliding of actin filaments over myosin filaments filling the middle of the A band.
Types of Skeletal Muscle Fibers
- Classified based on color and function (fast twitch or slow twitch).
- Differences: color, myoglobin content, source of energy, mitochondria number, and fatigue resistance.
Cardiac Muscle
- Forms the middle layer of the heart (myocardium).
- Thicker in the ventricles than in the atria.
- Surrounded by:
- Epicardium (visceral layer of the pericardium) - outside
- Endocardium - inside
- Cardiac muscle tissue is made up of branched and interconnected muscle fibers.
- Each fiber is surrounded by delicate connective tissue rich in capillaries (endomysium).
- Characterized by intercalated discs, which are specialized junctions between adjacent cardiac muscle cells.
Smooth Muscle
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Found in the walls of hollow viscera, blood vessels, and other structures.
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Small, non-branched spindle-shaped cells.
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Arranged in sheets or layers.
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Connected by gap junctions.
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Characterized by the presence of dense bodies forming an attachment site for contractile proteins (myosin) and lack of striations.
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Innervated by the autonomic nervous system (involuntary).
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Function: Slow, sustained contractions, influenced by hormones and autonomic nervous system, contraction that maintains blood vessel tone in cardiovascular, respiratory, and gastrointestinal systems.
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Regeneration: Limited ability to repair or regenerate after injury.
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Description
This quiz covers key concepts regarding muscular tissue, including its structure, types, and functions. Explore the details of skeletal, cardiac, and smooth muscles, as well as the cellular components vital for muscle function.