Question

Put the motor units (listed by innervation ratio) in order from first activated to last to be activated.

A 1:25
B 1:100
C 1:1000

Answer 1

Motor units are activated in an order based on their size and innervation ratio. The correct activation order is the smaller units first (1:25), followed by intermediate (1:100) and finally the larger units (1:1000). This reflects the body's method of producing precisely controlled muscle force.

Step-by-step explanation:

When it comes to the recruitment of motor units, motor units are activated based on the size principle, which means smaller motor units with lower innervation ratios get activated first, followed by larger motor units with higher innervation ratios. In the context of the motor units listed by innervation ratio (A: 1:25, B: 1:100, C: 1:1000) this would translate into the following activation order:

1. A (1:25) - Small motor unit with low innervation ratio, often associated with fine motor control.
2. B (1:100) - A motor unit of intermediate size and innervation ratio.
3. C (1:1000) - Large motor unit with high innervation ratio, typically recruited for gross, powerful movements.

This order of activation allows for gradual recruitmen, ensuring precise control over muscle force output.