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

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

Wave of Depolarization

Na + K+K+ K+K+ K+K+ K+K+ K+K+ K+K+ K+K+ K+K+ K+K+ K+K+

Wave of Depolarization

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

Electromyography (E.M.G.)

Motor & Sensory Neuron Anatomy

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