Parkinson’s Disease (PD) Neurological II Practice Exam

When a tendon is tapped, the muscle spindle is stretched and sends a rapid signal to the spinal cord, where it synapses directly on the alpha motor neurons. This creates a quick, involuntary muscle contraction in a monosynaptic pathway. That’s the deep tendon reflex, a hallmark of proprioceptive stretch within the muscle itself rather than skin or cortex-driven processing. It’s distinct from superficial reflexes, which are triggered by skin stimulation (like abdominal or plantar responses); pathological reflexes, which are abnormal signs of corticospinal tract dysfunction (such as Babinski); and cortical reflexes, which involve processing by the cerebral cortex and are not elicited by a simple tendon tap. So, reflexes elicited by tapping a tendon fall into the deep tendon reflex category.