Neuromuscular system

Muscle structure

Muscle → Muscle fibres → Myofibrils → Sarcomeres (Z-lines)

Fixator muscle

A muscle that works to provide stability to a movement

Muscle fibre types

I, IIa, IIx

Type 1 fibre

Slowest, small and red, low force production, fatigue resistant, long twitch durations

Type IIa fibre

Moderate size, pink, hybrid of power and duration, can increase in number through training, fast contraction speed, medium force production, high fatigue resistance

Type IIb fibre

Large and white, “super fast” twitch fibre, small blood supply, ATP/PC, 10-12s fatigue period

Recruitment of muscle fibres

Different amounts and types of muscle fibres are recruited based on the activity

The Size principle

Motor units are recruited in size order (I → IIa → IIb)

Impulse for recruitment

Generated at the cerebellum, travels down the spinal cord and moves along nerves to the motor units.

Motor unit

A motor neuron connected to one or many muscle fibres

Motor end plate

The part of the motor unit where the motor neuron joins to the muscle fibre (axon terminal)

Synaptic cleft

The gap between nerves and muscles

Neuromuscular neurotransmitter

Acetylcholine

All or none law

This law states that a muscle fibre cannot be partially contracted

Wave summation

Repeated stimulation of a nerve impulse with no time for relaxation

Tetanic contraction

A sustained muscle contraction that arise from fast, repeated releases of calcium from the muscle

Spatial contraction

A repeated stimulation over a period of time with periods of rest inbetween

PNF training

Proprioceptive Neuromuscular Facilitation. A form of flexibility training that creates autogenic inhibition.

CRAC

Contract-Relax, Agonist-Contract

Autogenic inhibition

Tricking the specialist proprioceptors at the muscle, the Golgi Tendon Organ and Muscle spindles to send conflicting impulses to the brain, which disengages the stretch reflex