1. ESS 303 – Biomechanics The Neurological System

2. 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

3. Size of Motor Units

5. Motor Units (Cont.) All fibers in a motor unit are of the same type: Slow (S): type I, slow conduction & contraction times Fatigue Resistant (FR): type IIa, moderate Contraction time Fast Fatigable (FF): type IIb, high conduction velocity and high speed of contraction

6. Wave of Depolarization

7. Na + K+K+ K+K+ K+K+ K+K+ K+K+ K+K+ K+K+ K+K+ K+K+ K+K+

8. Wave of Depolarization + + + + + + + + - - - - - - - - + + + + + + + + - - - - - - - - + + + - - -

10. Sarcolema Synaptic Cleft Postsynaptic Membrane Postsynaptic Membrane Presynaptic Membrane Junctional Folds Synaptic Vesicles Mitochondria The Neuromuscular Junction

12. Electromyography (E.M.G.)

13. Motor & Sensory Neuron Anatomy

14. The Spinal Cord

16. Proprioceptors Muscle Spindles: Length Golgi Tendon Organs: Tension Pacinian Corpuscles: Pressure

17. Muscle Spindle Structure

20. 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

21. 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