Normal reflexes suggest that the motor system is functioning appropriately. The main motor pathway, the corticospinal tract, descends from the cortex to different segments of the spinal cord. Neurons in this tract are upper motor neurons; the tract is also known as the pyramidal tract. The upper motor neurons synapse with lower motor neurons in the anterior gray matter of the spinal cord at the root level where the lower motor neuron exits. The corticospinal tract travels from the motor cortex through the internal capsule, and down the cerebral peduncles in the midbrain; it passes through the anterior pons, then crosses in the pyramids of the medulla, and follows the lateral corticospinal tract in the spinal cord.

Pathologically hyperactive reflexes imply disease in the corticospinal tract; an upper motor neuron disorder. Other signs of upper motor neuron disorder include spasticity, clonus, slow motor movements, and weakness of certain muscle groups (deltoid, triceps, wrist and finger extensors, hip flexors, knee flexors, and ankle dorsiflexors and evertors). An upgoing toe (a positive Babinski response) is a cardinal manifestation of upper motor neuron dysfunction. In the acute phase of an upper motor neuron lesion, hyporeflexia often is present, with hyperreflexia slowly developing over 1 to 2 weeks.