Final answer:
The muscle spindle apparatus serves as a muscle length detector.
Step-by-step explanation:
True.
The muscle spindle apparatus is a proprioceptive stretch receptor that lies within a muscle and detects the lengthening or stretching of the muscle.
It helps to maintain the muscle at an optimal length for efficient contraction.
The muscle spindles function as part of the stretch reflex, which is a protective mechanism that prevents muscle tearing and helps to maintain muscle tone.