Final answer:
The stretch reflex is an example of a negative feedback loop where a muscle contracts in response to stretching.
Step-by-step explanation:
This reflex helps maintain muscles at a constant length.The stretch reflex is an example of negative feedback loop. In this reflex, when a skeletal muscle is stretched, a muscle spindle receptor is activated, causing the muscle to contract.
At the same time, a collateral of the muscle spindle fiber inhibits the motor neuron of the antagonist muscles, preventing them from contracting. This reflex helps to maintain muscles at a constant length and is commonly exemplified by the knee je rk reflex.