ess 303 – biomechanics the neurological system. motor units a motor nerve and all the muscle...

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