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
Definition: Isomeric transition is a form of radioactive decay where a gamma photon is emitted by a nucleus in an excited metastable state. The photon is emitted when the energy of the excited nucleus drops to the lower, ground state.