Parasympathetic (vagal) nerves leave the vagal nuclei within the medulla as preganglionic efferent vagal fibers. These preganglionic efferent fibers are relatively long and do not synapse until they reach their target organ (e.g., the heart).
medical Definition of isovolumetric : of, relating to, or characterized by unchanging volume; especially: relating to or being an early phase of ventricular systole in which the cardiac muscle exerts increasing pressure on the contents of the ventricle without significant change in the muscle fiber length and the ventricular volume remains constant
operculum. 1. a lid or covering. 2. the folds of pallium from the frontal, parietal, and temporal lobes of the cerebrum overlying the insula. adj., adj operÂ´cular. dental operculum the hood of gingival tissue overlying the crown of an erupting tooth.n anatomy, the portions of the frontal (operculum frontale [TA], frontal operculum [TA]), parietal (operculum parietale [TA], parietal operculum [TA]), and temporal (operculum temporale [TA], temporal operculum [TA]) lobes bordering the lateral sulcus and covering the insula. 3.