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Chpt. 49

Chpt. 49. Muscles & Motor Locomotion. Why Do We Need All That ATP?. Function of Muscles:. To convert chemical energy of ATP into mechanical work, To get around… To get your food To digest your food To pump your heart so that oxygen can get to that mitochondria.

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Chpt. 49

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  1. Chpt. 49 Muscles & Motor Locomotion Why Do We Need All That ATP?

  2. Function of Muscles: • To convert chemical energy of ATP into mechanical work, • To get around… • To get your food • To digest your food • To pump your heart so that oxygen can get to that mitochondria

  3. Types of Muscle Tissue: • 1) Cardiac rapid contraction • 2) Skeletal rapid contraction • 3) Smooth slow sustained contraction

  4. involuntary, striatedauto-rhythmic voluntary, striated heart moves bone multi-nucleated involuntary, non-striated digestive systemarteries, veins evolved first

  5. As a side … • Insect flight muscles contract more rapidly than ANY OTHER • 1,000 contractions/second • Highest metabolic rate • Contain more mitochondria than any other tissue • HOW get oxygen???

  6. HOW DO WE MOVE THESE 206 BONES?

  7. SKELETAL MUSCLE

  8. skeletal muscles move bones by pulling…not pushing, therefore they come in antagonistic pairs:

  9. So in other words, in order to flex, you must contract your flexor muscles… and in order to, relax, you must contract the antagonistic muscle flexor vs. extensor

  10. Extensor (quadracep) Notice the TENDON connects the muscle to the bone. One bone is pulled towards another bone upon contraction.

  11. composed of smaller & smaller &smaller units Vertebrate Skeletal Muscle Structure: plasma membrane skeletal muscle nuclei tendon muscle fiber (cell) myofibrils myofilaments

  12. Vertebrate Skeletal Muscle each muscle fiber = one long, cylindrical, multinucleated cell

  13. Vertebrate Skeletal Muscle Bundle of fibers Muscle fibercells composed of: bundles of myofibrils (threadlike structures)

  14. Myofibrils are basically parallel “contractile units”

  15. Myofibrils consist of even smaller structures: thick filaments thin filaments

  16. myofibrils have a regular arrangement regular arrangement regular arrangement regular arrangement regular arrangement

  17. sarcomere = basic unit of a myofibril - hundreds are connected end to end & make up the myofibril

  18. sarcomeres are made of these proteins: thick filaments thin filaments

  19. Thin filaments: actin • Complex (bunch) of proteins: • braid of actin molecules & tropomyosinfibers • tropomyosin fibers secured with troponin complex • these are proteins

  20. Thick filaments: myosin • Single protein • myosin molecule • long protein with globular head bundle of myosin proteins: globular heads aligned

  21. Thick & thin filaments • Myosin tails aligned together & heads pointed away from center of sarcomere

  22. sarcomere = basic unit of a myofibril - hundreds are connected end to end & make up the myofibril

  23. SARCOMERE

  24. making up the sarcomere… Z-lines = the borders of the sarcomere (actin)

  25. at rest, thethickmyosin & thin actin filaments in the sarcomere do not overlap completely:

  26. area inwhich only thick myosin filaments = Hzone

  27. Area inwhich onlythin actin filaments = Iband

  28. Area in which both:thin actin filaments & thick myosin filaments= Aband

  29. More muscle anatomy: SARCOLEMMA = plasma membrane

  30. More muscle anatomy: Ttubule = inward extension of the plasma membrane

  31. More muscle anatomy: mitochondrion = ohh, there are plenty!

  32. More muscle anatomy: sarcoplasmicreticulum = another name for endoplasmic reticulum

  33. How does the Muscle Contract?

  34. Sliding Filament Model

  35. Motor Unit (Usually hundreds of muscle fibers)

  36. NEUROMUSCULAR JUNCTION

  37. NEUROTRANSMITTOR ~ ACETYLCHOLINEreleased as action potential moves to synaptic terminal of muscle fiber

  38. The acetylcholine causes the action potential to continue in the muscle fiber

  39. The action potential spreads into T-Tubules(invaginations in the membrane of the muscle fibers)

  40. The a.p. opens Ca+2 channels in the sarcoplasmic reticulum (e.r.)

  41. The special type of smooth endoplasmic reticulum found in smooth and striated muscle fibers whose function is to store and release calcium ions.

  42. Ca+2 flows & binds to a protein in the actin filament

  43. Sliding Filament Model Thin actin filament has myosinbindingsites… At restmyosinbindingsites are blocked (with trypomyosin)

  44. Sliding Filament Model Thin actin filament has myosinbindingsites… myosinbindingsites are opened when Ca+2 binds to the troponin. (Ca+2 is released as a result of acetylcholein rushing through the T-tubules)

  45. Sliding Filament Model At rest, myosin head is bound to an ATP -- ATP

  46. Sliding Filament Model when Ca+2 floods into the cell, Myosin head hydrolyzes (breaks) ATP to ADP and P --.

  47. Sliding Filament Model Myosin binds to Actin --  this forms a cross-bridge When this occurs, the myosin head changes shape and releases the ADP + P

  48. Sliding Filament Model the myosin head changes shape and releases the ADP + P

  49. Sliding Filament Model The thin actin filament is pulled toward the center of the sarcomere…

  50. Sliding Filament Model SLIDING

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