<prompt> The rigidity seen in Parkinsons disease is due toExcessive simulation of alpha motor neurons of all the muscles.Hypofunction of motor cortex.Absence of cerebellar inhibition.Increased sensitivity of stretch reflex.  <response>: D Increased sensitivity of stretch reflex. The hypokinetic features of Parkinsons disease are akinesia and bradykinesia, and the hyperkinetic features are rigidity and tremor. The absence of motor activity and the difficulty in initiating voluntary movements are striking. 