What are the afferents of origin of the human stretch reflex, and is it a purely spinal reaction?
D004558:Electric Stimulation; D004576:Electromyography; D006801:Humans; D009475:Neurons, Afferent / Q000502:physiology*; D012026:Reflex, Stretch; D013116:Spinal Cord / Q000502:physiology; D013933:Thumb; D014732:Vibration