Question

________ principle states that motor units are recruited in order according to their recruitment thresholds and firing rates?

a) Size principle
b) All-or-none principle
c) Graded response principle
d) Threshold principle

Answer 1

The size principle explains that motor units are activated in a specific order based on recruitment thresholds and firing rates, allowing skeletal muscles to produce graded muscle responses from delicate to forceful contractions.

Step-by-step explanation:

The principle that states motor units are recruited in order according to their recruitment thresholds and firing rates is known as the size principle. This principle is a vital component of muscle physiology and describes how motor units within skeletal muscles are activated.

Smaller, lower-threshold motor units with more excitable neurons are recruited first, producing a small degree of contractile strength. As more strength is required, larger motor units with bigger, higher-threshold motor neurons are engaged, resulting in the successive recruitment of motor units and increase in muscle contraction, also known as recruitment. The process allows fine motor control over muscle actions from delicate movements to powerful contractions. The graded muscle response and subsequent muscle strength result from this orderly recruitment of motor units.