Final answer:
In a life or death situation, the parasympathetic control of the heart rate is not taking place; instead, the sympathetic division is active, preparing the body for 'fight-or-flight'.
Step-by-step explanation:
In a life or death situation, the element that is not taking place is A) Parasympathetic control of the heart rate. During such intense situations, the sympathetic division of the autonomic nervous system is primarily active. It prepares the body for the 'fight-or-flight' response by causing an increase in heart rate, dilation of the pupils, release of catecholamines like epinephrine and norepinephrine (increasing blood pressure), and the suppression of non-essential functions like digestion.
On the other hand, the parasympathetic division takes over once the emergency passes to return the body to a state of 'rest and digest', slowing the heart rate and resuming digestive activities. This means that during a life-threatening situation, the parasympathetic system's contribution to heart rate control is minimal, if at all present.