Question

Describe the 3 different types of motor units.

explain muscle fiber recruitment.

Answer 1

A motor unit consists of the muscles fibres that are innervated by a single motor neuron.

It can be classified as :

Type l : type l motor unit are slow twitch. They are fatigue resistant and contains oxidative enzyme

Type lla : type lla motor unit contain fast  twitch muscle fibres. They have a moderate fatigue resistance. They contain oxidative as well as glycolytic enzymes.

Type llb : type llb motor unit contains rapidly contracting muscle fibres. They are fatigued easily. They contain glycolytic enzymes.
Muscle fibre recruitment can be defined as the activation of different motor units in a muscle to produce muscle contraction. Recruitment of large number of motor units results in a stronger muscle contraction whereas recruitment of less number of motor units results in weaker muscle contraction. Motor units are recruited according the size with smaller motor units recruited first.