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
pertaining to materials that allow x-rays to penetrate with a minimum of absorption. adjective Referring to a material or tissue that allows the facile passage of X-rays (i.e., has an air or near-air density); radiolucent structures are black or near black on conventional X-rays.