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MUSCLES

MUSCLES . Form is For Function. We See This in bones when we look at a vertebrae Processes are for attachment of muscles, tendons and ligaments. Openings such as foramen are for nerves and blood vessels. .

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MUSCLES

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  1. MUSCLES

  2. Form is For Function • We See This in bones when we look at a vertebrae • Processes are for attachment of muscles, tendons and ligaments. • Openings such as foramen are for nerves and blood vessels.

  3. We Can See Form For Function In Both TheGross and Microanatomy of Muscles!

  4. What Functions Do Muscles Provide?

  5. Smooth Muscle Characteristics • Has no striations • Spindle-shaped cells • Single nucleus • Involuntary – no conscious control • Found mainly in the walls of hollow organs Figure 6.2a

  6. Skeletal Muscle Characteristics • Most are attached by tendons to bones • Cells are multinucleate • Striated – have visible banding • Voluntary – subject to conscious control • Cells are surrounded and bundled by connective tissue

  7. Cardiac Muscle Characteristics • Has striations • Usually has a single nucleus • Joined to another muscle cell at an intercalated disc • Involuntary • Found only in the heart Figure 6.2b

  8. Characteristics of Muscles • Muscle cells are elongated (muscle cell = muscle fiber) • Contraction of muscles is due to the movement of microfilaments • All muscles share some terminology • Prefix myo refers to muscle • Prefix mys refers to muscle • Prefix sarco refers to flesh

  9. Skeletal Muscle Attachments • Epimysium blends into a connective tissue attachment • Tendon – cord-like structure • Aponeuroses – sheet-like structure • Sites of muscle attachment • Bones • Cartilages • Connective tissue coverings

  10. Connective Tissue Wrappings of Skeletal Muscle (So as to keep Muscle fibers together) • Endomysium – around single muscle fiber • Perimysium – around a fascicle (bundle) of fibers • Epimysium- The outermost connective tissue Figure 6.1

  11. Characteristics of Muscles: AND….MYO, MYS and SARCO • Muscle cells are elongated (muscle cell = muscle fiber) • Contraction of muscles is due to the movement of microfilaments • All muscles share some terminology: • Prefix myo refers to muscle • Prefix mys refers to muscle • Prefix sarco refers to flesh

  12. The myocyte is elongated Their characteristics depend on which type of muscle they are found: skeletal, muscle or cardiac. Which Type of Muscle are we referring to here?? Muscle Cell =Muscle Fiber= Myocyte: But BEWARE…ALL Muscles cells are NOT ALIKE!!

  13. Microscopic Anatomy of Skeletal Muscle Cell: A First Look • Cells are multinucleate • Nuclei are just beneath the sarcolemma Figure 6.3a

  14. We Will See The Role of Calcium During ……Muscle Contraction

  15. Smooth Endoplasmic Reticulum (SR) in Muscle Cells • VERY SPECIALIZED • It STORES and MOBILIZES Calcium ions • What is the role of Ca++ in muscle contraction??

  16. What Does the SER Look Like?

  17. Function of Muscles • Produce movement • Maintain posture • Stabilize joints • Generate heat

  18. Properties of Skeletal Muscle Activity • Irritability – ability to receive and respond to a stimulus • Contractility – ability to shorten when an adequate stimulus is received

  19. Muscle Contraction Begins When.. • Stored Calcium is released into the sarcoplasm • These ions are released into the sarcomeres

  20. Relaxed and Contracted Sarcomeres • Muscle cells shorten because their individual sarcomeres shorten • pulling Z discs closer together • pulls on sarcolemma • Notice neither thick nor thin filaments change length during shortening • Their overlap changes as sarcomeres shorten

  21. Microscopic Anatomy of Skeletal Muscle Sarcoplasmic reticulum – specialized endoplasmic reticulum Figure 6.3a

  22. Microscopic Anatomy of Skeletal Muscle • Myofibril • Bundles of myofilaments • Myofibrils are aligned to give distinct bands • I band = light band • A band = dark band Figure 6.3b

  23. Microscopic Anatomy of Skeletal Muscle • Sarcomere • Contractile unit of a muscle Figure 6.3b

  24. Microscopic Anatomy of Skeletal Muscle • Organization of the sarcomere • Thick filaments = myosin filaments • Composed of the protein myosin • Has ATPase enzymes Figure 6.3c

  25. Microscopic Anatomy of Skeletal Muscle • Organization of the sarcomere • Thin filaments = actin filaments • Composed of the protein actin Figure 6.3c

  26. Microscopic Anatomy of Skeletal Muscle • Myosin filaments have heads (extensions, or cross bridges) • Myosin and actin overlap somewhat Figure 6.3d

  27. Microscopic Anatomy of Skeletal Muscle • At rest, there is a bare zone that lacks actin filaments • Sarcoplasmic reticulum (SR) – for storage of calcium Figure 6.3d

  28. Neural Stimulus to Muscles • Skeletal muscles must be stimulated by a nerve to contract • Motor unit • One neuron • Muscle cells stimulated by that neuron Figure 6.4a

  29. Those Myofiloments: How They Move: The Basis of Muscle Contraction Plus: The Neuromuscular Junction: where it all happens: This IS Muscle Physiology!

  30. What Do You Think? • Glycogen- Stored form of starch found in muscle • What is the role of Glycogen in muscle physiology?

  31. SEE THE I BAND DISAPPEAR during a contraction of the.. sarcomere? Yes. Which makes up myofilament. Will the I band reappear? When? What causes the I band to dissapear? The Case of the Shrinking Sarcomere

  32. What is ACTUALLY happening when a Sacromere Shrinks? • The thin filament ACTIN and the THICK filament MYOCIN form a CROSS-BRIDGE that cause a SLIDING motion. • This shortens the sacromere or closes that GAP or I band and causes a CONTRACTION. • Neither the ACTIN nor the Myocin filament actually shorten its the sacromere itself.

  33. OBSERVE THE UNCOVERED ACTIN SITES…MYOCIN CAN NOW BIND…

  34. Before Contraction Can Happen • We must think about it …even if it is a reflex. • We must involve the CNS…

  35. Nerve Stimulus to Muscles • Skeletal muscles must be stimulated by a nerve to contract • Motor unit • One neuron • Muscle cells stimulated by that neuron Figure 6.4a

  36. MOTOREND PLATE • This is where the neuron and myofiber intercept. • Muscle contraction is possible because of neural impulse at the motor end plate. • It is the action potential that causes the release of Ca++ ions from the SR, • The Ca++ can then bind to Troponin and change the configuration of Tropomyocin. • ACTiN’s G binding sites are then exposed.

  37. Nerve Stimulus to Muscles • Synaptic cleft – gap between nerve and muscle • Nerve and muscle do not make contact • Area between nerve and muscle is filled with interstitial fluid Figure 6.5b

  38. Transmission of Nerve Impulse to Muscle • Neurotransmitter – chemical released by nerve upon arrival of nerve impulse • The neurotransmitter for skeletal muscle is acetylcholine • Neurotransmitter attaches to receptors on the sarcolemma • Sarcolemma becomes permeable to sodium (Na+)

  39. Transmission of Nerve Impulse to Muscle • Sodium rushes into the cell generates an action potential (AP) • The action potential travels along the T-tubules to the SR to stimulate release of Calcium ions.

  40. The SR Stores Ca ions and Release them When There is an AP! Find the T-Tubules

  41. Where do Ca ions go? • The ions travels to the muscle tissue and bind to the ACTIN regulatory proteins ( TROPONIN) . • This UNCOVERS Myosin Head BINDING Sites on ACTIN so as to allow CROSS BRIDGING ( once myosin is powered by ATP.

  42. The Sliding Filament Theory of Muscle Contraction • Activation by nerve causes myosin heads (crossbridges) to attach to binding sites on the thin filament • Myosin heads then bind to the next site of the thin filament Figure 6.7

  43. The Sliding Filament Theory of Muscle Contraction • This continued action causes a sliding of the myosin along the actin • The result is that the muscle is shortened (contracted) Figure 6.7

  44. The Sliding Filament Theory Figure 6.8

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