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Contractility

Properties of Muscle Tissue. 3 Types of Muscle Tissue. Skeletal – attached to bone. Contractility. Excitability. Cardiac – the heart. Extensibility. Smooth – internal organs blood vessels. Elasticity. Facts and Functions of Skeletal Muscle. Movement of Body

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Contractility

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  1. Properties of Muscle Tissue 3 Types of Muscle Tissue Skeletal – attached to bone • Contractility • Excitability Cardiac – the heart • Extensibility Smooth – internal organs blood vessels • Elasticity

  2. Facts and Functions of Skeletal Muscle • Movement of Body • Heat Production (Tb) • Protection of Body • About 40% body mass • Muscle fiber = Muscle cell One muscle cell (see next slide)

  3. A Muscle Fiber (Cell)

  4. Neuromuscular Junction of Skeletal Muscle

  5. Diagrammatic Neuromuscular Junction

  6. Excitation - Contraction in Skeletal Muscle

  7. Intracellular Ca2+ triggers contraction

  8. Sarcolemma Lateral sacs

  9. The Sarcomere

  10. Contractile Proteins Regulatory Proteins • Actin – “thin filaments” • 2 regulatory proteins associated with actin 1. Tropomyosin • guards active site on actin 2. Troponin • binds Ca2+ • Myosin – “thick filaments” • – ATPase site on head • – Actin binding site on head

  11. Structures of the Sarcomere Z disks H-band I-band A-band M line H-band = myosin only I-band = actin only A-band = all of the myosin

  12. Muscle Relaxation

  13. Sources of ATP in Muscle Tissue (Skeletal Muscle Metabolism) 2) Short Term – Glycolysis (Lactic Acid) 1) Immediate – Creatine Phosphate 3) Long Term – Oxidative Phosphorylation

  14. CP ADP P P Creatine Kinase ATP C 1)Creatine Phosphate (CP) • Takes P from creatine and sticks it on ADP • Makes ATP, but CP is very limited! (~ 6 seconds)

  15. 2) Glycolysis Krebs Cycle ETC Glucose (C6H12O6) 2 ADP Glycolysis + Lactic Acid 2 ATP Have O2 (30-40 sec) No O2 3) Oxydative Phosphorylation 36 ATP

  16. Where is ATP used in Muscle Tissue e.g., requires 1 ATP for every 2 Ca2+ imported to SR 1) Re-sequestering Ca2+ into the SR 2) Breaking the Crossbridge (Myosin-Actin bond) * Needed for relaxation or continuation of contraction

  17. Muscle Fatigue - Depletion of O2 - decrease in ATP available. Depletion of glucose or glycogen - decrease in ATP available. Slows Na+/K+ pumps, decreases RMP excitability. Lactic Acid Build-Up. Motor neuron exhaust ACh: "junctional fatigue". CNS (origin) "central fatigue", mentally exhausted.

  18. 1. Slow Twitch: Aerobic 2. Fast Twitch: Anaerobic - Slow onset of contraction - Fast onset of contraction - Slower to fatigue - Faster to fatigue - Smaller diameter - Larger diameter - More mitochondria - Fewer mitochondria - More capillaries - Fewer capilaries - Myoglobin - High glycogen stores - Posture, Endurance - Power lifting, Sprinting

  19. Comparison of Slow and Fast Twitch Muscle Fibers

  20. Varying the Force of Contraction(Graded Skeletal Muscle Contraction) 1) Temporal Summation 2) Spatial Summation 3) Length of Resting Sarcomere

  21. Length of Sarcomere and Tension Generation

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