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Chapter 3

Chapter 3. The Neuromuscular System: Anatomical and Physiological Bases and Adaptations to Training. Objectives. Describe the anatomy of the neural system Describe anatomy of the muscular unit Understand force production Understand reflexes Describe neuromuscular training adaptations.

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Chapter 3

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  1. Chapter 3 The Neuromuscular System: Anatomical and Physiological Bases and Adaptations to Training

  2. Objectives • Describe the anatomy of the neural system • Describe anatomy of the muscular unit • Understand force production • Understand reflexes • Describe neuromuscular training adaptations

  3. Nervous System • Anatomical divisions • Central nervous system • Peripheral nervous system • Functional divisions • Somatic (voluntary) • Autonomic (involuntary)

  4. Nerve conduction velocity • 120 m/s or 270mph for myelinated • 400 f/s • 5 m/s or 2mph for unmyelinated • 16 f/s

  5. 1014 neurons

  6. Reflexes • Involuntary motor response to a stimulus

  7. Stretch Shortening Cycle (SSC) • Concentric force is increased as a function of eccentric action or stretching. • Increased force with speed of the motion. • Stored elastic energy responsible. (rubber band)

  8. Muscle SpindleSensitive to stretch

  9. Golgi Tendon Organ (GTO)Sensitive to tension

  10. Striated Actin Myosin Troponin Tropomyosin Z lines H zone I band A band Muscle Tissue

  11. FIGURE 3.6

  12. Sliding Filament Theory of Muscle Contraction (AF Huxley, 1954) • Impulse initiated in cortex • Impulse travels through spinal cord • Through nervous pathway, action potential reaches myoneural junction • ACH is released from synapse and binds to receptors on muscle

  13. Sliding Filament Theory of Muscle Contraction (cont.) • Action potential spreads along sarcolema of muscle • Transverse tubules depolarize • Sarcoplasmic reticulum depolarizes and releases calcium into the sarcoplasm • Calcium causes conformational change in shape of troponin/tropomyosin

  14. Sliding Filament Theory of Muscle Contraction (cont.) • Myosin head binds to actin • Binding of actin to myosin causes the myosin head to swivel. • ATP breaks the actin/myosin bond and the myosin head moves to the next active site http://www.youtube.com/watch?v=CbfK1Gi-aCk&feature=fvwrel

  15. Electrical Stimulation • Motor nerve innervation • Latent period (.01) • Contraction phase (.04) • Relaxation phase (.05) • Fast vs. slow time varies • Motor Units (nerve and fibers)

  16. Event Timing by Gender

  17. Length Tension Relationship (Blix Curve 1880)

  18. Force/Velocity cure (AV Hill 1939)

  19. 2. Recruitment (size principle; Henneman, 1964) Gradation of Force 1. Rate coding (increasing the rate of firing of motor neurons)

  20. Muscle Actions Based on Length of Muscle • Isometric • Concentric • Eccentric

  21. Muscle Modes Based on Velocity of Shortening • Isometric • Isotonic (DCER) • Isokinetic

  22. Muscular Strength Adaptations • Specificity (isokinetic, isotonic, isometric) • Males vs. females • Absolute strength, males are stronger • Expressed per unit of cross sectional area, small differences

  23. Muscular Strength Adaptations • Hypertrophy • Atrophy • Hyperplasia • Sarcopenia

  24. Bilateral/Unilateral Strength • Unilateral cross-education • 60% increase in untrained limb • Bilateral deficit • Inhibitory mechanism

  25. Muscle Strength Adaptations • Muscle fiber transformation • Motor Units • Type I can not be converted to type II • Type II can not be converted to type I • Type II X fibers are converted to type II A with resistance training • Implications of this conversion are unclear

  26. Muscle Strength Adaptations (cont.) • Nervous systems adaptations • If there is no increase in muscle size, strength increases are likely neural • RFD (Rate of Force Development) sports .3-.4 secs • Increased frequency of firing • Increased synchronization of motor unit firing • Relaxation of antagonistic muscle groups

  27. Early strength gains in resistance training are neural (Moritani and deVries, 1979) • Patterns of motor unit recruitment • Recruiting more motor units

  28. Metabolic Adaptations • Metabolic specificity • ATP/phospagens • Glycogen • Glycolytic enzymes (PFK) Endocrine Adaptations • Testosterone • Growth hormone

  29. Next Class • Chapter 4 Skeletal System

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