Question

What kind of neurons control skeletal muscles? What is a motor unit? How and why does the number and size of motor units differ in “precision” muscles versus “power” muscles.

Answer 1

1. Aplha motor neurons control the skeletal muscle. They are also called lower motor neurons. They can cause muscle contraction and generate movement.
2. Motor unit is composed of motor neuron and skeletal muscle that the neuron innervates. It includes the single motor neuron and the associated muscle fiber.
3. The number of motor units varies with the type of muscle, that affects the precision and power. Precision is inversely proportional to the motor unit size. A small number of motor units can have greater precision moves compared to larger complexes. When operated at maximum velocity, the force generated does not peak, in fact, reduces due to the absence of actin-myosin cross-bridges. We know that power = force x velocity. But an optimal combination of motor units and velocity is required to generate maximum power. Usually to generate higher power a large number of motor units are required. So we can say that a small number of motor units functioning at a time can bring about small but precise movement, but large power can be generated by the combined action of multiple motor units.