| a pulsation of the heart, including one complete systole and diastole |
| an innate mechanism of the body that regulates its rhythmic and periodic cycles |
voluntary vol·un·tar·y (vŏl'ən-těr'ē)
adj.
Arising from or acting on one's own free will.
Normally controlled by or subject to individual volition, as of respiration.
Capable of making choices; having the faculty of will.