Reflexes and Gait

The importance of proprioception to motor function is revealed by the dramatic story of Ian Waterman, a man who lost function in all proprioceptive and tactile spinal afferents. The circuitry of the stretch reflex, termed the deep tendon reflex in clinical circles, is described in detail. In this context, the student is introduced to load, muscle spindles, Ia afferents, α‎- and γ‎- motoneurons, and α‎- γ‎ coactivation. The concept of physiological extensors and flexors is useful for understanding the role of reflexes in normal and abnormal postures. The logic and utility of reflex testing is fully explained and the Ib and nociceptive withdrawal reflexes briefly introduced. Primitive reflexes and their modulation across development and in response to stroke or disease are presented. In a final segment, movements produced by central pattern generators and refined by reflexes are illustrated by a close examination of human gait across the life cycle.