Nerve fibres of the parasympathetic nervous system arise from the central nervous system. Specific nerves include several cranial nerves, specifically the oculomotor nerve, facial nerve, glossopharyngeal nerve, and vagus nerve. Three spinal nerves in the sacrum (S2-4) also act as parasympathetic nerves.
The word longevity is sometimes used as a synonym for life expectancy in demography - however, the term longevity is sometimes meant to refer only to especially long-lived members of a population, whereas life expectancy is always defined statistically as the average number of years remaining at a given age.
Studies have shown for nearly 20 years that the key personality trait that predicts longevity is conscientiousness. In one long-term study, students judged by their parents and teachers to be conscientious as 12-year-olds were more likely to be alive when researchers followed up 64 years later.