Chapter10 muscletissuemarieb

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Chapter10 muscletissuemarieb

  1. 1. Ch 10: Skeletal Muscle Tissue (Myology) main objectives:1) Describe the distinguishing characteristics of the different muscle tissues2) Discuss the organization of skeletal muscle3) Explain the micro-anatomy of a skeletal muscle fiber4) Describe the fascicle arrangement in different types of muscle5) Review general muscle terminology Developed by John Gallagher, MS, DVM
  2. 2. Types of Muscle TissueOne of the 4 primary tissue types• Skeletal = Striated = Voluntary • 40 % of weight• Cardiac (involuntary)• Smooth (involuntary, nonstriated Made up of many tissue types. > 700 skeletal muscles Musculus = little mouse Word roots: sarco myo
  3. 3. Function of Skeletal Muscles1. Skeletal movement2. Posture and body position3. Support of soft tissues4. Joint Stabilization5. Guarding of entrances & exits6. Maintenance of body temperature7. Protection8. Facial expression
  4. 4. Gross to Microscopic AnatomyEach skeletal muscle cell (fiber) is wrapped by 3 layers ofconnective tissue.
  5. 5. Epi-, Peri-, and Endomysium Epimysium = On top of theAre interwoven - muscle Continuous with tendon, and Perimysium = Around a bundle eventually the periosteum of myofibersDistinguish between: Endomysium = Surrounds each Tendon myofiber Aponeurosis LigamentFunction: Protection Blood supply Innervation
  6. 6. Nerve and Blood SupplySkeletal muscles are rich in nerves and blood vessels.Chemical communication at neuromuscular junctionSynaptic terminal of axon meets motor end plate of muscle cellCoiled capillaries are able to adapt to changes in length of muscle fiber
  7. 7. CoiledCapillaries
  8. 8. Origin and Insertion•Origin: •The part that stays still •Usually proximal•Insertion: •The part that moves •Usually distal
  9. 9. Microanatomy of Skeletal Muscle FibersSome vocabulary:Skeletal muscle cell = fiber or myofiberSarcolemmaSarcoplasm Multiple nuclei on peripherySarcoplasmic reticulumMyofibrilMyofilamentsT-tubules
  10. 10. Fig. 10.4 Microanatomy Myofiber (= cell) Myofibrils Myofilaments
  11. 11. MyofilamentsMyofiber (cell) Myofibrils Myofilaments Actin & Myosin
  12. 12. Sarcomere (= thick + thin filaments)Thick and Thin Filaments are organized in repeating functional unitsEach myofibril has linear arrangement of up to 10,000 sarcomeresBanded appearance (striation) due to arrangement of thick and thin filamentsInteraction of thick and thin filaments responsible for skeletal muscle fiber contraction
  13. 13. SarcomereStructure Z - line I - band A- band = lIght band = dArk band
  14. 14. Thin Filament: Actin
  15. 15. Thick Filament: Myosin
  16. 16. Motor Unit= All muscle fibers that are controlled by a single motor neuron (axon)The lower the ratio of muscle fibers to neurons, the more precise the movement can be.Ratio is from 1:1 to 1:2000Acetylcholine is the neurotransmitter at the motor end plateContraction of a motor unit is “all or none.”
  17. 17. Neuromuscular Junction LM x230
  18. 18. Muscle ControlMuscle tone = Resting tension of skeletal muscles (continuous contraction of some motor units to maintain some muscle tension)Recruitment or Multiple motor unit summation for greater forceSome directional control depending on which motor units are stimulated
  19. 19. Muscle Hypertrophy vs. AtrophyHypertrophy due to anaerobic exerciseLeads to increased muscle size - how?Atrophy if supply of myofilaments exceeds demand. Muscle fibers become smaller and weaker.Eventual death of muscle fibers is irreversible! Importance of Physical Therapy
  20. 20. Three Types of Skeletal Muscle Fibers (fast, slow, intermediate)1. Slow (or Red) OxidativeFibers Type I2. Fast Glycolytic Fibers Type Iix3. Fast Oxidative Fibers Type IIaMost skeletal muscles containmixture of fiber types.Proportion of fast to slow depends ontraining and developmentOne motor unit only containsone fiber type
  21. 21. 1. Slow (or Red) Oxidative Fibers Type ISlow but continuous contraction for extended periodsSmaller diameter (~ half) contain myoglobin more capillaries more mitochondriaDo not fatigue as fast due to aerobic production of ATP
  22. 22. 2. Fast Glycolytic FibersType IIxFast contraction after nervous stimulationLarge diameter large glycogen reserve fewer mitochondria densely packed myofibrilsFatigue fast due to mainly anaerobic respiration
  23. 23. 3. Fast Oxidative FibersType IIa Have attributes in between fast and slow types
  24. 24. Organization (shape) of Skeletal Muscle FibersEffect of individual muscle contraction determined by: 1. arrangement of muscle fibers 2. method of attachment to skeletonBundles of muscle fibers =fascicleMuscle fibers within 1 fascicle are parallel
  25. 25. Parallel MusclesExtensor vs. flexorOrigin vs. InsertionSpindle shaped with cord-like tendonsSome flat bands with broad attachments on each end
  26. 26. Convergent musclesBroad origin, pointed insertionDirection of pull can be varied: versatility!!Example = deltoid
  27. 27. Pennate Muscles: UnipennateOne or more tendons run though muscle bodyFascicles in oblique angle to tendonCan generate more tensionExample = biceps brachii
  28. 28. Pennate Muscles: Bipennate & Multipennate Example Example
  29. 29. Muscle TerminologyFlexor ExtensorOrigin InsertionAgonist AntagonistSynergist Possible: multiple origins Note: Agonist = Prime Mover
  30. 30. Grouping of Muscles according to Primary ActionAgonist = Prime MoverAntagonist (action opposes agonist)Synergists = Assistants of prime mover
  31. 31. Cardiac Muscle• Form the Myocardium• Striated, involuntary• Single cells • Branched extensively • Joined with Intercalated Disks (provide communication with gap junctions)• Similar filament structure to Skeletal M. • Not as organized • Nuclei in the middle of the cells
  32. 32. Smooth Muscle• Nonstriated, involuntary• Internal organs (mostly)• Single Cells called fibers• Often in opposing layers • Gut, bladder

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