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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

Chapter 3

The Neuromuscular System: Anatomical and Physiological Bases and Adaptations to Training

objectives
Objectives
  • Describe the anatomy of the neural system
  • Describe anatomy of the muscular unit
  • Understand force production
  • Understand reflexes
  • Describe neuromuscular training adaptations
nervous system
Nervous System
  • Anatomical divisions
    • Central nervous system
    • Peripheral nervous system
  • Functional divisions
    • Somatic (voluntary)
    • Autonomic (involuntary)
slide5

Nerve conduction velocity

    • 120 m/s or 270mph for myelinated
      • 400 f/s
    • 5 m/s or 2mph for unmyelinated
      • 16 f/s
reflexes
Reflexes
  • Involuntary motor response to a stimulus
stretch shortening cycle ssc
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)
muscle tissue
Striated

Actin

Myosin

Troponin

Tropomyosin

Z lines

H zone

I band

A band

Muscle Tissue
sliding filament theory of muscle contraction af huxley 1954
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
sliding filament theory of muscle contraction cont
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
sliding filament theory of muscle contraction cont1
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

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

2. Recruitment (size principle; Henneman, 1964)

Gradation of Force

1. Rate coding (increasing the rate of firing of motor neurons)

muscle actions based on length of muscle
Muscle Actions Based on Length of Muscle
  • Isometric
  • Concentric
  • Eccentric
muscle modes based on velocity of shortening
Muscle Modes Based on Velocity of Shortening
  • Isometric
  • Isotonic (DCER)
  • Isokinetic
muscular strength adaptations
Muscular Strength Adaptations
  • Specificity (isokinetic, isotonic, isometric)
  • Males vs. females
    • Absolute strength, males are stronger
    • Expressed per unit of cross sectional area, small differences
muscular strength adaptations1
Muscular Strength Adaptations
  • Hypertrophy
  • Atrophy
  • Hyperplasia
  • Sarcopenia
bilateral unilateral strength
Bilateral/Unilateral Strength
  • Unilateral cross-education
    • 60% increase in untrained limb
  • Bilateral deficit
    • Inhibitory mechanism
muscle strength adaptations
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
muscle strength adaptations cont
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
slide30

Early strength gains in resistance training are neural (Moritani and deVries, 1979)

    • Patterns of motor unit recruitment
    • Recruiting more motor units
metabolic adaptations
Metabolic Adaptations
  • Metabolic specificity
    • ATP/phospagens
    • Glycogen
    • Glycolytic enzymes (PFK)

Endocrine Adaptations

  • Testosterone
  • Growth hormone
next class
Next Class
  • Chapter 4 Skeletal System
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