MICROANATOMY

Detailed explanation-1: -Because an action potential generated by a motor neuron normally brings to threshold all of the muscle fibers it contacts, a single motor neuron and its associated muscle fibers together constitute the smallest unit of force that can be activated to produce movement.

Detailed explanation-2: -A single motor neuron, however, can innervate many muscle fibers. The combination of an individual motor neuron and all of the muscle fibers that it innervates is called a motor unit.

Detailed explanation-3: -When a motor neuron is activated, all of the muscle fibers innervated by the motor neuron are stimulated and contract. The activation of one motor neuron will result in a weak but distributed muscle contraction.

Detailed explanation-4: -A motor unit is made up of a motor neuron and all of the skeletal muscle fibers innervated by the neuron’s axon terminals, including the neuromuscular junctions between the neuron and the fibres.

Detailed explanation-5: -A single action potential from a motor neuron will produce a single contraction in the muscle fibers of its motor unit. This isolated contraction is called a twitch. A twitch can last for a few milliseconds or 100 milliseconds, depending on the muscle type.