What is a primary spinal level for the Achilles tendon reflex?

The primary spinal level for the Achilles tendon reflex is S1, making the fourth choice the correct response. The Achilles tendon reflex tests the integrity of the S1 and S2 nerve roots, with S1 being the main contributor. When the Achilles tendon is tapped, sensory receptors in the tendon are stimulated, sending signals through the sensory nerve fibers to the spinal cord, where this information synapses with motor neurons that then send impulses back to the gastrocnemius and soleus muscles. This results in the rapid contraction of these muscles, causing plantarflexion of the foot.

Recognizing the specific spinal levels tested by reflexes is essential for understanding the underlying neurological pathways and diagnosing potential issues. In this case, S1 plays a crucial role in the Achilles reflex, illustrating the functional importance of these nerve roots in lower limb biomechanics and response to stimuli.