Final answer:
As intracranial pressure rises, the heart rate acutely increases, mean arterial pressure typically increases, and brainstem herniation may occur.
Step-by-step explanation:
As intracranial pressure rises, several physiological changes occur in response. One of these changes is an acute increase in heart rate (option c). The increase in heart rate is a reflex response of the sympathetic division of the autonomic nervous system, triggered by the drop in blood pressure upon standing. This reflex is known as the orthostatic reflex and helps to maintain blood pressure against the effect of gravity when standing up.
Mean arterial pressure, on the other hand, typically increases with rising intracranial pressure, rather than decreases (option b). Increased intracranial pressure can also result in brainstem herniation, particularly if left untreated or if the pressure continues to rise without intervention (option d). Herniation occurs when the brain is compressed and forced to move through openings in the skull.
In summary, as intracranial pressure rises, the heart rate acutely increases, mean arterial pressure typically increases, and brainstem herniation may occur.