Which nerve root is associated with the Achilles reflex?

The nerve root associated with the Achilles reflex is S1. This reflex is a deep tendon reflex tested during a neurological examination, and it helps assess the integrity of the associated nerve roots and the spinal cord segments involved in reflex activity.

When the Achilles tendon is tapped with a reflex hammer, it stimulates the S1 nerve root, which corresponds to the gastrocnemius and soleus muscles in the calf responsible for plantar flexion of the foot at the ankle joint. The reflex involves a sensory pathway that carries the information from the stretch receptors in the tendon to the spinal cord, where it synapses with motor neurons originating from the S1 root. This results in the contraction of the calf muscles and the downward movement of the foot.

Other nerve roots mentioned, such as L2, L4, and C5, are related to different muscle groups and reflexes. For instance, L2 is associated with hip flexion, L4 is linked to knee extension, and C5 is connected to shoulder abduction. However, none of these nerves are involved in the Achilles reflex, which specifically relies on the functional integrity of the S1 nerve root.