Studying the vertebrate stretch reflex is a good way to introduce students to the topics of stretch receptors, nerve conduction velocity, electromyograms (EMG), and motor control. Specialized receptors in the muscle respond to the stretching of the tendon attached to the muscle, and then send signals to motorneurons through a single synapse. The muscle fibers depolarize and twitch (contract) in response to the incoming impulse from the motorneuron.