What are muscle spindles?
D002490:Central Nervous System / Q000502:physiology; D006801:Humans; D009046:Motor Neurons; D009068:Movement; D009470:Muscle Spindles / Q000033:anatomy & histology* / Q000502:physiology / Q000503:physiopathology; D009132:Muscles / Q000294:innervation*; D009422:Nervous System Diseases / Q000503:physiopathology