Chapter 13 - Section 13.3 - Figure 13.22 - The Patellar Tendon Reflex Arc and Reciprocal Inhibition of the Antagonistic Muscle - Page 499: 1

Fig. 12:22 Somatic motor neurons to skeletal muscles are capable only of excitation of those muscles.

To facilitate contraction of the qudriceps, it is necessary to relax the hamstrings . Impulses sent from interneurons inhibit motor neurons to the hamstrings at the level of the central nervous system (CNS).