Which nerve is primarily responsible for the Achilles reflex?

Which nerve is primarily responsible for the Achilles reflex?

• A. Sciatic nerve
• B. Tibial nerve (S1)
• C. Femoral nerve
• D. Common fibular nerve

Answer: (B)

The Achilles reflex centers on the plantarflexion of the foot driven by the tibial nerve. When the Achilles tendon is tapped, stretch receptors in the gastrocnemius-soleus complex send an afferent signal through the tibial nerve to the spinal cord, and a motor signal travels back via the tibial nerve to the same muscles, producing contraction and plantarflexion. This reflex mainly involves the S1–S2 spinal levels, so the tibial nerve is the key efferent pathway for this response. The sciatic nerve contains the tibial nerve, but the direct motor supply for this reflex is the tibial portion. The femoral nerve would affect the knee-extending reflex, and the common fibular nerve would influence other movements, not plantarflexion.

The Achilles reflex centers on the plantarflexion of the foot driven by the tibial nerve. When the Achilles tendon is tapped, stretch receptors in the gastrocnemius-soleus complex send an afferent signal through the tibial nerve to the spinal cord, and a motor signal travels back via the tibial nerve to the same muscles, producing contraction and plantarflexion. This reflex mainly involves the S1–S2 spinal levels, so the tibial nerve is the key efferent pathway for this response. The sciatic nerve contains the tibial nerve, but the direct motor supply for this reflex is the tibial portion. The femoral nerve would affect the knee-extending reflex, and the common fibular nerve would influence other movements, not plantarflexion.