Question

What makes up a motor unit?

a/ one tendon and one muscle fiber

b/ fast- and slow-twitch muscle fibers

c/ one motor nerve connected to muscle fibers

d/ one motor nerve connected to a tendon

Answer 1

Answer--c) one motor nerve connected to muscle fibres

Explanation--

Motor unit-

Motor unit consists of a single motor neuron, it's axonal branches and all the muscle fibres supplied by them.

Size of the motor unit :

The size of the motor unit can be large or small depending upon the the number of muscle fibres innervated by them.

In the intrinsic muscles of hand, one motor neurons innervates less than 10 muscle fibres so, stimulation of a motor unit produces small rise in tension.

The back muscles have 100 or even thousands of muscle fibres per unit, where activation of single motor unit causes a large increase in tension.

Recruitment of motor units -

The process of activating more number of motor units is called recruitment of motor units.