The Achilles reflex corresponds to which nerve roots?

The Achilles reflex corresponds to which nerve roots?

• A. L5 to S1
• B. L4 to L5
• C. S1 to S2
• D. L3 to L4

Answer: (A)

Achilles reflex tests the sacral nerve roots, mainly S1 with some contribution from S2. The reflex arc travels through the tibial nerve to the gastrocnemius-soleus muscles, so tapping the Achilles tendon should produce plantar flexion if these sacral pathways are intact. The strongest single contributor is S1, with S2 assisting. Roots around L4-L5 or L3-L4 affect other reflexes (like the knee jerk) and are not the primary mediators of the ankle jerk. Therefore, the Achilles reflex corresponds to the S1–S2 nerve roots.

Achilles reflex tests the sacral nerve roots, mainly S1 with some contribution from S2. The reflex arc travels through the tibial nerve to the gastrocnemius-soleus muscles, so tapping the Achilles tendon should produce plantar flexion if these sacral pathways are intact. The strongest single contributor is S1, with S2 assisting. Roots around L4-L5 or L3-L4 affect other reflexes (like the knee jerk) and are not the primary mediators of the ankle jerk. Therefore, the Achilles reflex corresponds to the S1–S2 nerve roots.