INNERVATION OF MUSCLE-SPINDLES IN SNAKE, ELAPHE-QUADRIVIRGATA

  • 1 January 1976
    • journal article
    • research article
    • Vol. 122  (SEP) , 141-167
Abstract
The morphology and distribution of sensory and motor endings in 2 varieties of muscle spindles in the snake, E. quadrivirgata, were examined. For sensory endings Ag impregnation technique was used. The sensory terminal was composed of terminal bulbs and small links. In long-capsule spindles the sensory ending was arranged longitudinally in 1 or 2 rows. The sensory ending in short-capsule spindles ramified extensively, densely covering the intrafusal fiber. The area occupied by sensory bulbs was estimated to be slightly higher in short-capsule (15-17%) than in long-capsule spindles (12-13%). Motor innervation was studied using AchE [acetylcholinesterase] staining for light microscopy in conjunction with EM. In the polar region of either type of spindle, the majority of the motor endings were of the grape type. In long-capsule spindles plate endings may occur in the spindle pole and in the capsular region. Motor endings in the capsular region were mostly of the plate type. Plate endings rarely occurred in short-capsule spindles. Identified single motor endings were studied by EM. Intrafusal grape endings were characterized by a smooth post-synaptic membrane. Intrafusal plate endings in the polar region were characterized by junctional folds or gutterings; plate endings in the capsular region showed less developed gutterings or indentations. The distributions of intrafusal motor endings was examined along the length of single intrafusal fibers. The long-capsule spindle often received asymmetrical motor innervation around the capsular region, whereas motor endings in the short-capsule spindle distributed more symmetrically.