ess 303 – biomechanics the neurological system. motor units a motor nerve and all the muscle...
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ESS 303 – Biomechanics
The Neurological System
Motor Units
A motor nerve and ALL the muscle
fibers (cells) it innervates
All or nothing – force and unit size
Recruitment patterns
From small to large
Rate Coding: higher rate higher force
Size of Motor Units
Size of Motor Units
Motor Units (Cont.)
All fibers in a motor unit are of the same type:Slow (S): type I, slow conduction &
contraction timesFatigue Resistant (FR): type IIa, moderate
Contraction timeFast Fatigable (FF): type IIb, high
conduction velocity and high speed of contraction
Wave of Depolarization
Wave of Depolarization
Na+ Na+ Na+ Na+ Na+ Na+ Na+ Na+ Na+
Na+ Na+ Na+ Na+ Na+ Na+ Na+ Na+ Na+
K+ K+ K+ K+ K+
K+ K+ K+ K+ K+
Na+
Na+
Na+
Na+
Wave of Depolarization
+ + + + + + + + + + + + + + + +
- - - - - - - - - - - - - - - -
+ + + + + + + + + + + + + + + +
- - - - - - - - - - - - - - - -
+ + +
+ + +
- - -
- - -
SarcolemaSarcolema
Synaptic CleftSynaptic CleftPostsynapticMembranePostsynapticMembrane
PresynapticMembrane
Junctional FoldsJunctional Folds
SynapticVesicles
Mitochondria
The Neuromuscular Junction
Electromyography (E.M.G.)
Motor & Sensory Neuron Anatomy
The Spinal Cord
The Spinal Cord
Proprioceptors
Muscle Spindles: Length
Golgi Tendon Organs: Tension
Pacinian Corpuscles: Pressure
Muscle Spindle Structure
The Stretch-Shortening Cycle
Elastic qualities of muscle tissue and tendons
Greater contraction force possible if muscle is put “on stretch” with an eccentric contraction just prior to a concentric contraction
Examples: Running, vertical jumps, wind-ups, etc.
The neurological component
Proprioceptive neuromuscular facilitation (PNF) Stretching
Currently the fastest and most effective way known to increase static-passive flexibility
A muscle group is passively stretched, then contracts isometrically against resistance while in the stretched position, and then is passively stretched again through the resulting increased range of motion
Fatigue of stretch-reflex (from muscle spindles) and use of IPSP from GTOs