1 / 151

Chapter 10: Muscle Tissue

Chapter 10: Muscle Tissue. Muscle Tissue. A primary tissue type, divided into: skeletal muscle Voluntary striated muscle, controlled by nerves of the central nervous system cardiac muscle Involuntary striated muscle smooth muscle Involuntary nonstriated muscle.

Télécharger la présentation

Chapter 10: Muscle Tissue

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.


Presentation Transcript

  1. Chapter 10:Muscle Tissue

  2. Muscle Tissue • A primary tissue type, divided into: • skeletal muscle • Voluntary striated muscle, controlled by nerves of the central nervous system • cardiac muscle • Involuntary striated muscle • smooth muscle • Involuntary nonstriated muscle

  3. Characteristics of all Muscle Tissues • Specialized Cells: - elongated, high density of myofilaments = cytoplasmic microfilaments of actin and myosin • Excitability/Irritability: - receive and respond to stimulus • Contractility: - shorten and produce force upon stimulation • Extensibility: - can be stretched • Elasticity: - recoil after stretch

  4. Skeletal Muscle Tissue • Skeletal muscles make up 44% of body mass • Skeletal muscle = an organ • composed of: • skeletal muscle cells (fibers) and CT • nerves and blood vessels

  5. Functions of Skeletal Muscles • Produce skeletal movement • Maintain posture and upright position • Support soft tissues • Guard entrances and exits • Maintain body temperature by generating heat • Stabilize joints

  6. Muscle Tissue Organized at the Tissue Level

  7. Formation of Skeletal Muscle Fibers • Skeletal muscle cells are called fibers Figure 10–2

  8. Skeletal Muscle Anatomy • Each muscle is innervated by one nerve: • Nerve must branch and contact each skeletal muscle fiber (cell) • One artery, branches into extensive capillaries around each fiber: • supply oxygen • supply nutrients • remove wastes.

  9. Organization of Connective Tissues Figure 10–1

  10. Organization of Connective Tissues • Muscles have 3 layers of connective tissues that hold the muscle together: • Epimysium - covers the muscle (exterior collagen layer), separates muscle from other tissues, composed of collagen, connects to deep fascia • Perimysium - composed of collagen and elastin, has associated blood vessels and nerves, bundles muscle fibers into groups called fascicles - perimysium covers a fascicle • Endomysium - composed of reticular fibers, contains capillaries, nerve fibers and satellite cells (= stem cells  repair), surrounds individual muscle fibers

  11. Muscle Attachments • Endomysium, perimysium, and epimysium come together: • at ends of muscles • to form connective tissue attachment to bone matrix • Tendon = cord-like bundles • Aponeurosis = sheet-like

  12. How would severing the tendon attached to a muscle affect the muscle’s ability to move a body part? Uncontrolled movement would result from a severed tendon. Movement would be greatly exaggerated with no tendon. No movement is possible without a muscle to bone connection. Limited movement would result.

  13. Muscle

  14. Skeletal Muscle Fibers • Huge cells: • up to 100 µm diameter, 30 cm long • Multinucleate • Formed by fusion of 100s of myoblasts • Nuclei of each myoblast retained to provide enough mRNA for protein synthesis in large fiber • Unfused myoblasts in adult = satellite cells • Satellite cells are capable of division and fusion to existing fibers for repair but cannot generate new fibers

  15. Organization of Skeletal Muscle Fibers Figure 10–3

  16. Skeletal Muscle Fibers • Cell membrane = sarcolemma • Sarcolemma maintains separation of electrical charges resulting in a transmembrane potential • Na+ pumped out of the cell creating positive charge on the outside of the membrane • Negative charge from proteins on inside give muscle fibers a resting potential of -85mV • If permeability of the membrane is altered, Na+ will flow in causing a change in membrane potential • Change in potential will signal the muscle to contract

  17. Transverse Tubules • Tubes of sarcolemma called transverse tubules (T tubules) reach deep inside the cell to transmit changes in transmembrane potential to structures inside the cell • Transmit action potential through cell • Allow entire muscle fiber to contract simulataneously

  18. Skeletal Muscle Fibers • Cytoplasm = sarcoplasm: • rich in glycosomes (glycogen granules) and myoglobin (binds oxygen) • Fiber is filled with myofibrils extending the whole length of the cell • Myofibrils consist of bundles of myofilaments • Myofilaments are responsible for muscle contraction • made of actin and myosin proteins • 80% of cell volume

  19. Organization of Skeletal Muscle Fibers Figure 10–3

  20. Skeletal Muscle Fibers • Actin: • makes up the thin filament • Myosin: • makes up the thick filament • When thick and thin filaments interact, contraction occurs

  21. Skeletal Muscle Fibers Sarcoplasm contains networks of SER called sarcoplasmic reticulum (SR) • Sarcoplasmic Reticulum: • A membranous structure surrounding each myofibril • Function: • store calcium and help transmit action potential to myofibril • SR forms chambers (terminal cisternae) attached to T-tubules • Cisternae • Concentrate Ca2+ (via ion pumps) • Release Ca2+ into sarcomeres to begin muscle contraction • All calcium is actively pumped from sarcoplasm to SR (SR has 1000X more Ca2+ than sarcoplasm)

  22. Skeletal Muscle Fibers • Triads are located repeated along the length of myofilaments • Triads = T-tubule wrapped around a myofibril sandwiched between two terminal cisternae of SR • Formed by 1 T tubule and 2 terminal cisternae of SR • Triads are located on both ends of a sarcomere • Sarcomere = smallest functional unit of a myofibril

  23. Sarcomere

  24. Each muscle = ~ 100 fascicles • Each fascicle = ~ 100 muscle fibers • Each fiber (cell) = ~ 1 thousand myofibrils • Each myofibril = ~ 10 thousand sarcomeres

  25. The structural components of a sarcomere.

  26. Sarcomeres • The contractile units of muscle • Structural units of myofibrils • Form visible patterns within myofibrils

  27. Sarcomeres Composed of: 1. Thick filaments – myosin 2. Thin filaments – actin 3. Stabilizing proteins: -hold thick and thin filaments in place 4. Regulatory proteins: - control interactions of thick and thin filaments Organization of the proteins in sarcomere causes striated appearance of the muscle fiber Figure 10–4

  28. Muscle Striations • A striped or striated pattern within myofibrils: • alternating dark, thick filaments(A bands) and light, thin filaments(I bands)

  29. Regions of the Sarcomere • A-band: - whole width of thick filaments, looks dark microscopically • M line: at midline of sarcomere - Center of each thick filament, middle of A-band - Attaches neighboring thick filaments • H-zone: - Light region on either side of the M line - Contains thick filaments only • Zone of overlap: - ends of A-bands - place where thin filaments intercalate between thick filaments (triads encircle zones of overlap)

  30. Regions of the Sarcomere • I-band: - Contains thin filaments outside zone of overlap - Not whole width of thin filaments • Z lines/disc: - the centers of the I bands - constructed of Actinins - Anchor thin filaments and bind neighboring sarcomeres - Constructed of Titin Proteins - Bind thick filaments to Z-line, stabilize the filament

  31. Why does skeletal muscle appear striated when viewed through a microscope? Z lines and myosin filaments align within the tissue. Glycogen reserves are linearly arranged. Capillaries regularly intersect the myofibers. Actin filaments repel stain, appearing banded.

  32. Sarcomere Function • Transverse tubules encircle the sarcomere near zones of overlap • Ca2+ released by SR causes thin and thick filaments to interact • Muscle Contraction • Is caused by interactions of thick and thin filaments • Structures of protein molecules determine interactions

  33. Thin Filament Figure 10–7a

  34. Thin Filaments (5-6 nm diameter) • Made of 4 proteins: • Actin • Nebulin • Holds F actin strands together • F-actin (filamentous) consists of rows of G-actin (globular) • Each G-actin has an active site that can bind to myosin • Tropomyosin - Covers the active sites on G actin to prevent actin–myosin binding • Troponin: holds tropomyosin on the G-actin • Also has receptor for Ca2+: • when Ca2+ binds to the troponin-tropomyosin complex it causes the release of actin allowing it to bind to myosin

  35. Troponin and Tropomyosin Figure 10–7b

  36. Initiating Contraction • Ca2+ binds to receptor on troponin molecule • Troponin–tropomyosin complex changes • Exposes active site of F actin

  37. Thick Filament Figure 10–7c

  38. Thick Filaments (10-12 nm diameter) • Composed of: • bundled myosin molecules • titin strands that recoil after stretching • Each Myosin has three parts 1. Tail: - tails bundled together to make length of thick filament - all point toward M-line 2. Hinge: - flexible region, allows movement for contraction

  39. Thick Filaments (10-12 nm diameter) 3. Head: - hangs off tail by hinge, will bind actin at active site. - No heads in H-zone - also contains core of titin: - elastic protein that attaches thick filaments to Z-line - Titin holds thick filament in place and aid elastic recoil of muscle after stretching - Each thick filament is surrounded by a hexagonal arrangement of thin filaments with which it will interact

  40. The Myosin Molecule Figure 10–7d

  41. Myosin Action • During contraction, myosin heads: • interact with actin filaments, forming cross-bridges • pivot, producing motion

  42. Sliding Filaments Figure 10–8

  43. Sliding Filament Theory Contraction of skeletal muscle is due to thick filaments and thin filament sliding past each other • not compression of the filaments • H-zones and I-bands decrease width during contraction • Zones of overlap increase width • Z-lines move closer together • A-band remains constant Sliding causes shortening of every sarcomere in every myofibril in every fiber Overall result = shortening of whole skeletal muscle

  44. The components of the neuromuscular junction, and the events involved in the neural control of skeletal muscles.

  45. Skeletal Muscle Contraction • Excitation • Excitation-Contraction Coupling • Contraction • Relaxation Figure 10–9 (Navigator)

  46. Excitation and the Neuromuscular Junction • Excitation of muscle fiber is controlled by the nervous system at the neuromuscular junction using neurotransmitter

  47. The Neuromuscular Junction • Is the location of neural stimulation • Action potential (electrical signal): • travels along nerve axon • ends at synaptic terminal

  48. Components of Neuromuscular Junction Neuromuscular Junction: - where a nerve terminal interfaces with a muscle fiber at the motor end plate - one junction per fiber: control of fiber from one neuron • Synaptic Terminal: - expanded end of the axon, contains vesicles of neurotransmitters  Acetylcholine (Ach) • Motor End Plate: - specialized sarcolemma that contains Ach receptors and the enzyme acetylcholinesterase (AchE) • Synaptic Cleft: - space between the synaptic terminal and motor end plate where neurotransmitters are released

  49. Skeletal Muscle: Neuromuscular Junction Figure 10–10a, b (Navigator)

More Related