These muscle reflexes normally help maintain tone, and set the background tension of postural muscles which is needed for the performance of voluntary movements. To test these reflexes, the tendon of a muscle is tapped, causing the muscle to stretch. Sensory endings of large mechanoreceptor ganglion cell axons in the muscle spindles are stimulated. Central processes of these ganglion cells synapse directly on the motoneurons of the muscle being stretched. These excitatory synapses excite the motoneurons, leading to contraction of that muscle. Stretch reflexes are also referred to as monosynaptic reflexes or deep tendon reflexes.