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Muscle Tissue

Types of Muscle Tissue. Skeletal Muscle: this muscle type is primarily attached to bones. It is striated and voluntary.Cardiac Muscle: this forms the walls of the heart. It is striated and involuntary.Smooth Muscle: this is located in viscera. It is nonstriated (smooth) and involuntary.. Func

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Muscle Tissue

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    1. Muscle Tissue

    2. Types of Muscle Tissue Skeletal Muscle: this muscle type is primarily attached to bones. It is striated and voluntary. Cardiac Muscle: this forms the walls of the heart. It is striated and involuntary. Smooth Muscle: this is located in viscera. It is nonstriated (smooth) and involuntary.

    3. Functions of Muscle Tissue Through contraction, muscle tissue performs four important functions: motion, stabilizing body positions, regulating organ volume and generation of heat.

    4. Characteristics of Muscle Tissue Excitability or irritability—the ability to respond to certain stimuli by producing electrical signals called action potential or impulses. Contractility—the ability to shorten and thicken (contract), generating force to do work. Extensibility—the ability to be extended or stretched without damaging the tissue. Elasticity—the ability to return to original shape after contraction or extension.

    5. Anatomy of Skeletal Muscle Tissue Nerve and blood supply: Nerves that contain motor neurons convey impulses for muscular contractions. Blood provides nutrients and oxygen for contraction. The term “fascia” is applied to a sheet or broad band of fibrous connective tissue underneath the skin (superficial fascia) or around muscles and organs of the body (deep fascia.)

    6. Connective Tissue Components Other connective tissue components are epimysium, covering the entire muscle. Perimysium covers fasciculi Endomysium covers individual msucle fibers ALL are extensions of deep fascia

    7. Tendons and Aponeuroses Tendons and aponeuroses are all extensions of connective tissue beyond muscle cells that attach the muscle to bone or other muscle. Synovial sheaths enclose certain tendons and allow them to slide back and forth more easily. Tenosynovitis—an inflammation of the tendon sheaths and synovial membranes of certain joints, especially those of the wrists, shoulders, elbows, fingers and ankles.

    8. The Motor Unit A motor neuron and the muscle fibers it stimulates form a motor unit. A single motor unit may innervate as few as 10 or as many as 2000 muscle fibers, with an average of 150 fibers being innervated by each motor neuron.

    9. The Neuromuscular Junction A motor neuron transmits a nerve impulse (action potential) to a skeletal muscle where the nerve impulse serves as a stimulus for contraction. Excitable cells (neurons and muscle fibers) make contact and communicate at specialized regions called synapses.

    10. The Neuromuscular Junction A neuromuscular junction or NMJ or myoneural junction refers to an axon terminal of a motor neuron and the portion of the muscle fiber sarcolemma in close approximation with it (the motor end plate.) Acetylcholine or Ach is released by the synaptic vessicles of a motor neuron, triggering a muscle’s action potential.

    11. Microscopic Anatomy of Muscle Skeletal muscle consists of fibers (cells) covered by a sarcolemma . The fibers contain sarcoplasm, nuclei, sarcoplasmic reticulum, and transverse tubules. Each fibers contain myofibrils that consist of thin and thick filaments or myofilaments.

    12. Microscopic Anatomy of Muscle Filaments are compartmentalized into sarcomeres. Thin filaments are composed of actin, tropomyosin and troponin. Thick filaments are composed of mostly of myosin. Actin and myosin are the two contracile proteins in muscle.

    13. Microscopic Anatomy of Muscle Tropomyosin and troponin are muscle’s regulatory proteins. Projecting myosin heads are called cross bridges and contain actin and ATP-binding sites. Elastic filaments help stabilize the position of thick filaments.

    14. Recent Research Findings on Muscle Physiology A recent report published in Cell Metabolism by Hulver et al. indicates that severely obese people have three times as much of the fat-building enzyme stearoyl-CoA desaturase-1 or SCD-1 in their muscles than do their leaner counterparts. This may explain why obese people have trouble loosing weight or maintaining weight loss even when they cut their calories. However, exercise tends to override the muscles tendency to accumulate fat because it encourages the body to burn fat.

    15. Recent Research Findings on Muscle Physiology According to studies performed at Yale University Hospital’s Cardiothoracic Surgery unit, heart attack patients who have bypass surgery right after their attacks are at a significantly greater risk of dying than those who wait at least one week. There are two reasons why patients should wait: (1) the heart muscle is very stiff after a heart attack which can make surgery difficult and (2) abnormal heart rhythms that are often seen following a major heart attack can cause complications which could result in a heart attack during surgery or other serious complications.

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