The diagram shows a reflex arc.

A patient undergoes a procedure where a localized anaesthetic is injected to block nerve impulses. The goal is to temporarily prevent any movement or contraction of the leg muscle (motor block) while ensuring the patient still retains full sensation, such as feeling touch or pain (sensory pathways remain fully functional).
Where should the anaesthetic be injected to achieve this?
At X
At Y
At Z
At both X and Y