The Jendrassik maneuver will heighten (exaggerate) the patellar (knee-jerk) reflex by counteringsome of the normal descending inhibitory brainstem inputs to reflex arc interneurons. Synaptic delay isnot appreciably shortened, but a larger number of reflex arc neurons become activated due to removalof descending inhibition and the reflex response occurs a few milliseconds earlier. The amplitude of theresponse is increased because a larger number of motor units have been activated.