spindle [AS, spinel, to spin] , 1. the fusiform-shaped body of achromatin in the cell nucleus during the late prophase and the metaphase of mitosis. It consists of tiny fibers radiating out from the centrosomes and connecting them with one another. 2. a type of brain wave, consisting of a short series of changes in electric potential with a frequency of 14 per second. 3. any one of the special receptor organs comprising the neurotendinous and neuromuscular spindles distributed throughout the body. These kinds of spindles serve as special receptor organs that detect the degree of stretch in a muscle or at the junction of a muscle with its tendon and are essential in maintaining muscle tone.
