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Muscular Tissue

Muscular Tissue. Types of Muscle Tissue. skeletal cardiac smooth. Skeletal. attached to bones, skin, deep fascia, or other muscles voluntary control striated , alternating light and dark bands along length of myofibrils many nuclei Functions: - movement - posture - respiration.

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Muscular Tissue

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  1. Muscular Tissue

  2. Types of Muscle Tissue • skeletal • cardiac • smooth

  3. Skeletal • attached to bones, skin, deep fascia, or other muscles • voluntary control • striated , alternating light and dark bands along length of myofibrils • many nuclei • Functions: - movement - posture - respiration

  4. Skeletal Muscle Nuclei Striation

  5. Cardiac • located only in the heart • striated, single nucleus, branched fibers with intercalated discs • involuntary control by autonomic nervous system • regulation of heart rate is primarily due to hormones and neurotransmitters • no regeneration capability • propels blood through blood vessels

  6. Cardiac Muscle intercalated disc

  7. Smooth • located in hollow organs, skin attached to hair follicles, etc. • no striations, single nucleus, spindle-shaped fibers • involuntary control by autonomic nervous system • some regeneration

  8. Functions of Smooth Muscles • mix and propel food though GI tract • regulate flow of blood by changing diameter of lumen • contraction of urinary bladder, gallbladder, and spleen, expels urine, bile and blood • control sphincter muscles • control muscles of eye • contraction of arrector pili muscles

  9. Types of Smooth Muscles

  10. Multiunit Smooth • muscle fibers are not well organized • occur as separate fibers rather than sheets • found in irises of eye, walls of blood vessels

  11. Visceral Smooth • composed of sheets of spindle-shaped cells • in contact with one another • more common type • found in hollow visceral organs • capable of stimulating each other • display rhythmicity due to self-exciting fibers - responsible for peristalsis

  12. Peristalsis • wavelike motion • occurs in various tubular organs • helps force contents of these organs along their lengths

  13. Contraction of Smooth Muscles • acetylcholine and norepinephrine • also affected by hormones • slower to contract - slower to relax • can maintain a forceful contraction longer than skeletal with same amount of ATP • can change length without changing tautness

  14. Smooth Muscle

  15. Muscle Fibers • many muscle fibers are enclosed in a delicate connective tissue sheath called endomysium • several sheathed fibers are wrapped in perimysium in bundles called fascicles (10 -100 fibers)

  16. Muscle Fibers (cont.) • many fascicles are joined together by even tougher covering called epimysium • fascia covers entire muscles which lead into tendons which attach to bones

  17. Individual Muscle Fiber (single cell) • sarcolemma - plasma membrane covering of muscle cell • sarcoplasm - cytoplasm of a skeletal muscle cell

  18. Individual Muscle Fiber (cont.) • sarcoplasmic reticulum - network of membranous channels - within sarcoplasm (corresponds to endoplasmic reticulum) - surrounds each myofibril - channels run parallel to myofibril - stores calcium which is necessary for muscle contraction

  19. Individual Muscle Fiber (cont.) • transverse tubules - fingerlike inward invaginations or channels of sarcolemma - extend from membrane and pass through the fiber - open to outside of the muscle fiber - contain extracellular fluid - carry action potentials to sarcoplasmic reticulum

  20. Individual Muscle Fiber (cont.) • cisternae - enlarged portions of sarcoplasmic reticulum - lie on either side of transverse tubules - near region where actin and myosin overlap

  21. Individual Muscle Fiber (cont.) • myofibrils - long ribbon-like organelles - lie parallel to one another • myofilaments - thread-like structures within myofibrils (contain two types of protein filaments) • actin (thin & light) and myocin (thick & dark)

  22. Actin and Myosin • appear as light (thin) and dark (thick) bands • arrangement of these fibers produces the characteristic striations of a skeletal muscle fiber • slide past each other causing muscle cells to contract

  23. Myosin • located within the dark portions of the striations (A bands)

  24. Actin • located primarily within light areas (I bands) • during muscle contraction actin filaments slide farther into A bands • attached to the Z lines at end of I bands • Z lines extend across muscle fiber enabling adjacent myofibrils to lie side by side • segment between two Z lines is called a sarcomere

  25. Sarcomeres • repeating units composed of filaments inside myofibrils • do not extend the entire length of the muscle fiber

  26. Muscle Activity

  27. Characteristics of Muscle Tissue • excitability • contractility • extensibility • elasticity

  28. Excitability(irritability) • ability to respond to stimuli • generate action potentials or impulses • stimuli that initiate action potentials in muscles are neurotransmitters • neurotransmitters are released by axon terminals of neurons

  29. Contractility • ability to contract and shorten to generate a force • muscles contract in response to action potentials

  30. Extensibility • ability to be stretched or extended when pulled • with pairs of skeletal muscles - one muscle is contracted while the opposing one is usually stretched

  31. Elasticity • ability to return to original shape after contraction or extension

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