title: Site of origin of calcium spike in frog muscle spindle.
abstract: In order to define the site of origin of the calcium spike along the sensory nerve terminal of the frog muscle spindle, changes in the amplitude of the spikes during long-lasting polarizations of the nerve terminal were compared with those of full-sized and abortive spikes which occurred spontaneously. The amplitude of the calcium spikes superimposed on a spindle potential was not modifiable by application of polarizing currents of 6 nA or less, as well as that of the abortive spikes; while the amplitude of the full-sized spikes depended upon the polarizations. These results suggest that the calcium spikes may initiate along the non-myelinated filaments, as in the abortive spike, in contrast with the full-sized spikes to generate at the terminal node of the myelinated axon.
mesh_terms: D000344:Afferent Pathways / Q000502:physiology; D000818:Animals; D002118:Calcium / Q000378:metabolism*; D005071:Evoked Potentials; D009470:Muscle Spindles / Q000502:physiology*; D009412:Nerve Fibers / Q000502:physiology; D009413:Nerve Fibers, Myelinated / Q000502:physiology; D011898:Ranidae; D011901:Ranvier's Nodes / Q000502:physiology; D012964:Sodium / Q000378:metabolism
chemical_list: D012964:Sodium; D002118:Calcium