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Questions and Answers
What is the origin of muscular tissue in the body?
What is the name of the cell membrane of a myofiber?
What is the function of the sarcoplasm?
What is the name of the structure that surrounds a muscle fiber?
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What is the classification of muscular tissue based on?
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What is the shape of skeletal muscle fibers when viewed under a light microscope?
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What is the name of the structural and functional unit of the muscle fiber?
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What is the name of the system formed by a transverse tubule and two terminal cisternae of sarcoplasmic reticulum?
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Where are gap junctions found in the cardiac muscle?
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What is the main function of Purkinje fibers?
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What happens to cardiac muscle fibers when they die?
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What is the characteristic shape of smooth muscle fibers?
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How do smooth muscle fibers contract?
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What is the origin of new smooth muscle fibers?
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What is the function of the T-tubular system in skeletal muscle?
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Which type of skeletal muscle fibers are highly vascular and can sustain contraction for a long time without fatigue?
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What is the source of energy for Type I fibers?
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What is the characteristic of the muscle fiber in cardiac muscle?
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What is the function of the motor nerve supply in skeletal muscle?
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Which type of muscle fibers predominate in skeletal muscles?
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What is the characteristic of the sarcoplasm in cardiac muscle fibers?
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What is the location of the T-tubular system in cardiac muscle fibers?
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Study Notes
Muscular Tissue
- Muscular tissue is one of the basic tissues of the body, originating from mesoderm.
- A muscle cell, also called a myofiber, is elongated and has a cell membrane called sarcolemma and cytoplasm called sarcoplasm.
- Sarcoplasm contains all cell organoids (mainly actin and myosin micro-filaments) and inclusions (mainly fat and glycogen).
Structure of Muscle Fiber
- Muscle fibers are surrounded by a connective tissue sheath called endomysium.
- Groups of muscle fibers are called muscle bundles, surrounded by perimysium.
- The whole muscle is surrounded by epimysium.
Types of Muscular Tissue
- There are three types of muscular tissue: Skeletal muscle, Cardiac muscle, and Smooth muscle.
Skeletal Muscle
- Sites: attached to skeleton, diaphragm, tongue, eye, and upper third of esophagus.
- Characteristics: long, cylindrical shape with multiple peripheral flattened nuclei.
- Functional unit: sarcomere, formed of actin and myosin filaments.
- During muscular contraction, actin filaments slide over myosin filaments, resulting in shortening of the sarcomere.
- Myofibrils show alternation of dark (A-band) and light (I-band) areas.
- T-tubular system: regulates calcium ion concentration and conducts wave of depolarization to myofibrils.
- Nerve supply: motor nerve supply (motor-end plate) and sensory supply (muscle spindle).
- Muscle fibers can regenerate by activating new myoblasts cells called satellites.
Types of Skeletal Muscle Fibers
- Type I fibers (Red fibers): small diameter, high mitochondria and myoglobin content, slow contraction, sustainable for long time without fatigue, energy derived from fatty acid oxidation.
- Type II fibers (White fibers): large diameter, low mitochondria and myoglobin content, fast contraction, easily fatigued, energy derived from glycolysis.
- Type III fibers (Intermediate fibers): intermediate characteristics between Type I and Type II fibers.
Cardiac Muscle
- Sites: forms the wall of the heart (myocardium).
- Characteristics: short, cylindrical, branched, and joined at intercalated discs.
- Single rounded central nucleus, sarcoplasm with all cell organoids and inclusions.
- Cross striations of dark and light bands, similar to skeletal muscles.
- T-tubular system: formed of two tubules, lies at the Z-lines.
- Gap junctions: allow ions and electrical impulses to pass between cardiac muscle fibers.
- Purkinje fibers: modified cardiac muscle fibers responsible for conduction of nerve impulses.
- Muscle fibers, when died, never regenerate but are replaced by fibrous connective tissue.
Smooth Muscle
- Sites: wall of gastro-intestinal tract, respiratory system, urinary system, media of blood vessel wall, and capsule of spleen, lymph node, and digestive glands.
- Characteristics: spindle-shaped, central oval nucleus, acidophilic sarcoplasm.
- Sarcoplasm contains all cell organoids, inclusions, and long actin with few short myosin microfilaments.
- Cells are joined together with gap junctions, allowing electrical impulses to pass.
- Cells can regenerate from pericyte cells around blood vessels.
- Contraction occurs by translocation of actin and myosin filaments after ATP cleavage.
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Description
Learn about the basic characteristics of muscular tissue, including its origin, cell structure, and components. Understand the role of myofibers, sarcolemma, and sarcoplasm in muscle function.
