Final answer:
Muscle spindles detect rapid muscle length change and cause an increase in muscle tension, while Golgi tendon organs detect an increase in muscle tension and cause slow muscle length change.
Step-by-step explanation:
The correct answer is A. MS - rapid muscle length change, GT - increase in muscle tension.
Muscle spindles are stretch receptors that detect changes in muscle length. When there is a rapid muscle length change, the muscle spindle detects this and sends signals to the brain to increase muscle tension to protect the muscle from injury.
Golgi tendon organs, on the other hand, are tension receptors that detect the force of muscle contraction. When there is an increase in muscle tension, the Golgi tendon organ sends signals to the brain to decrease muscle tension to prevent excessive force and potential damage to the muscle.