1 / 153

Muscles and Muscle Tissue

Muscles and Muscle Tissue. Karen Marshall, Associate Professor Montgomery College Takoma Park Campus. Muscle Tissues. highly cellular well-vascularized three types differ in structure, body location, function, means of activation (contraction) skeletal cardiac smooth.

tegan
Download Presentation

Muscles and 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.

E N D

Presentation Transcript


  1. Muscles and Muscle Tissue Karen Marshall, Associate Professor Montgomery College Takoma Park Campus

  2. Muscle Tissues • highly cellular • well-vascularized • three types • differ in structure, body location, function, means of activation (contraction) • skeletal • cardiac • smooth

  3. Similarities (Skeletal & Smooth Muscle) • 1) cells • elongated • called muscle fibers • 2) muscle contraction • dependent on two kinds of myofilaments • actin • myosin • 3) muscle terms • myo, mys, sarco • sarcolemma ~ PM of muscle • sarcoplasm ~ muscle fiber cytoplasm

  4. Skeletal Muscle Tissue • voluntary, striated • packed by connective tissue sheets into skeletal muscles • fibers are longest • stripes (striations) • location • attached to and covers bony skeleton • controlled voluntarily

  5. Skeletal Muscle Tissue • contracts rapidly • tires easily • must rest after short periods of activity • function • responsible for overall body mobility • *see Table 9.4 for comparison of muscle types

  6. Cardiac Muscle Tissue • striated, involuntary • location • found only in heart • constitutes the bulk of the heart wall • controlled involuntarily • neural control allows a shift into high gear for short periods

  7. Cardiac Muscle Tissue • cells • uninucleate • branch & fit tightly together at junctions (intercalated discs) • contracts at a steady rate • pacemaker of heart (SA node)

  8. Smooth Muscle Tissue • nonstriated, involuntary • location • walls of hollow visceral organs • stomach, urinary bladder, respiratory passages • function • force fluids & other substances through internal body channels • controlled involuntarily • contractions are slow & sustained

  9. Functions of Muscle • 1) produce movement • 2) maintain posture • 3) stabilize joints • 4) generate heat • during contraction

  10. Functional Characteristics of Muscle • 1) excitability • irritability • ability to receive & respond to a stimulus • stimulus • environmental change that arises inside or outside the body • usually a chemical • NT, hormone, change in pH • response • generation of electrical impulse • passes along the sarcolemma contraction of muscle cells

  11. Functional Characteristics of Muscle • 2) contractility • ability of a muscle to shorten forcibly when adequately stimulated • 3) extensibility • ability of a muscle to be stretched or extended • even beyond its resting length when relaxed • 4) elasticity • ability of a muscle fiber to recoil & resume its resting length • after being stretched

  12. Gross Anatomy of Skeletal Muscle • each skeletal muscle is a discrete organ • consists of several kinds of tissues • muscle fibers predominate • blood vessels • nerve fibers • connective tissue

  13. Connective Tissue Wrappings • muscle fibers are wrapped & held together by several different layers • three layers • external to internal • epimysium • perimysium & fascicles • endomysium

  14. Connective Tissue Wrappings • epimysium • overcoat • dense irregular connective tissue • surrounds the entire muscle

  15. Connective Tissue Wrappings • perimysium & fascicles • muscle fibers are grouped into bundles of sticks • fascicle • each fascicle surrounded by a layer of fibrous connective tissue • perimysium

  16. Connective Tissue Wrappings • endomysium • surrounds each muscle fiber w/in a fascicle • consists of connective tissue & mostly reticular fibers

  17. Connective Tissue Wrappings • all connective sheaths continuous • one another • tendons (join muscles to bones) • w/ contraction • fibers pull on the sheath movement

  18. Connective Tissue Wrappings • functions • support each cell • reinforce muscle as a whole • contribute to elasticity of tissue

  19. Connective Tissue Wrappings (fig 9.1)

  20. Nerve & Blood Supply • each muscle • one nerve • an artery • one or more veins • enter or exit near the central part of the muscle • branch throughout the connective tissue • provide for normal muscle activity

  21. Attachments • direct (fleshy) • epimysium of muscle is fused to • periosteum of a bone • connective tissue covering • perichondrium of a cartilage • fibrous connective tissue covering

  22. Attachments • indirect • muscle’s connective tissue wrapping extend beyond muscle • ropelike tendon • connects muscle to bone • sheetlike aponeurosis • connects muscle to other muscles or to bones • tendon or aponeurosis • anchors the muscle to connective tissue covering • bone or cartilage or fascia of other muscles

  23. Attachments • indirect • much more common • durable & small • tendons are mostly tough collagenic fibers • cross bony projections • more tendons can pass over a joint • conserve space

  24. Microscopic Anatomy of a Skeletal Muscle Fiber • muscle fiber • long, cylindrical cell • multiple oval nuclei • ~multinucleate • arranged just beneath sarcolemma (PM) • functions as a syncytium

  25. Microscopic Anatomy of a Skeletal Muscle Fiber • myofibril • rodlike bundle of contractile filaments • ~hundreds to thousands in a single muscle fiber • make up 80% of cell volume

  26. Microscopic Anatomy of a Skeletal Muscle Fiber • striations • repeating series of dark A bands and light I bands • nearly perfectly aligned • give cells its striped (striated) appearance • located along length of each myofibril

  27. Microscopic Anatomy of a Skeletal Muscle Fiber • sarcomere • smallest contractile unit of a muscle fiber • consists of thick (myosin) filaments & thin (actin) filaments • arranged in a regular array • region of myofibril between two successive Z discs (lines)

  28. Microscopic Anatomy of a Skeletal Muscle Fiber • Z disc ~ Z line • darker area of midline interruption in the I band • coin-shaped sheet • composed of proteins • connectins • anchors the thin filaments • connects each myofibril to the next throughout the width of muscle cell

  29. Microscopic Anatomy of a Skeletal Muscle Fiber • thick filaments • composed primarily of protein myosin • each molecule has a rodlike tail terminates in two globular heads • head • AKA crossbridges • serve as actin binding sites • contain ATP binding sites & ATPase enzymes that split ATP to generate energy for contraction • link the thick & thin myofilaments together during contraction

  30. Microscopic Anatomy of a Skeletal Muscle Fiber • thick filaments • myosin molecules are bundled together • tails form central part of the filament • heads face outward & in opposite directions at each end

  31. Microscopic Anatomy of a Skeletal Muscle Fiber • thin filaments • composed chiefly of actin • polypeptide subunits of actin • AKA globular actin or G actin • contain active sites to which myosin crossbridges attach during contraction

  32. Microscopic Anatomy of a Skeletal Muscle Fiber • thin filaments • also contains regulatory proteins • help to control myosin-actin interactions involved in contraction • two strands of tropomyosin • troponin

  33. Tropomyosin • rod-shaped protein • spirals about actin core • helps stiffen it • successive molecules arranged end to end along actin filaments • relaxed muscle • block actin’s active sites • so myosin heads cannot bind to thin filaments

  34. Troponin • three polypeptide complex • one inhibitory subunit • binds to actin • one positioning subunit • binds to tropomyosin • helps position it onto actin • one subunit binds to Ca

  35. Myosin Molecule (fig 9.3a)

  36. Actin Molecule (fig 9.4c)

  37. Actin & Myosin Filaments (fig 9.3d)

  38. Regulation of Contraction • assisted by two sets of intracellular tubules • located in skeletal muscle fibers • sarcoplasmic reticulum • SR • transverse tubules • T tubules

  39. Sarcoplasmic Reticulum (SR) • specialized ER of muscle cells • interconnecting tubules • surround each myofibril • most run longitudinally along the myofibril • others form larger, perpendicular cross channels at A-I junctions • terminal cisternae (end sacs)

  40. Sarcoplasmic Reticulum (SR) • function • regulate IC levels of ionic Ca • store Ca and release it on demand • when muscle fiber is stimulated to contract • Ca provides the final “go” signal for contraction

  41. Transverse Tubules (T tubules) • elongated tube • invaginations of sarcolemma • run between terminal cisternae of SR formation of triads • successive groupings of three membranous structures • terminal cisternae • T tubule • terminal cisternae

  42. Transverse Tubules (T tubules) • function • conduct impulses to the deepest regions of the muscle cell & to every sarcomere • signal for release of Ca from adjacent terminal cisternae • act as a “rapid telegraphy system” • ensures that every myofibril in muscle fiber contracts at the same time

  43. SR & T tubules (fig 9.4)

  44. Contraction • physiological definition • activation of myosin’s crossbridges • force generating sites

  45. Contraction • shortening occurs • force or tension generated by cross bridges on the thin filaments > forces opposing shortening • shortening ends • cross bridges become inactive & tension generated declines • relaxation of muscle fiber

  46. Tropomyosin • rod-shaped protein • spirals about actin core • helps stiffen it • successive molecules arranged end to end along actin filaments • relaxed muscle • block actin’s active sites • so myosin heads cannot bind to thin filaments

  47. Troponin • three polypeptide complex • one inhibitory subunit • binds to actin • one positioning subunit • binds to tropomyosin • helps position it onto actin • one subunit binds to Ca

More Related