Final answer:
Increased intracranial pressure (ICP) generally causes an increase in blood pressure (BP) due to the body's compensatory Cushing reflex, while the heart rate (HR) might decrease because of increased parasympathetic activity.
Step-by-step explanation:
When intracranial pressure (ICP) increases, the body's autonomic response typically leads to an increase in blood pressure (BP) as a compensatory mechanism, a phenomenon known as Cushing's reflex. This reflex is an effort to maintain cerebral perfusion despite the elevated ICP. Often, with very high ICP, the heart rate (HR) may decrease due to increased parasympathetic activity as part of the reflex.
The body perceives an increase in ICP as a threat to cerebral blood flow; therefore, the autonomic nervous system responds by increasing systemic blood pressure to ensure that the brain remains oxygenated. This initial elevation in blood pressure serves to overcome the increased intracranial pressure. Eventually, if left unchecked, continued elevation in ICP can lead to herniation of brain tissues and subsequent damage, with potentially lethal consequences.
Moreover, the association between high ICP and changes in heart rate can vary depending on the underlying cause and the body's autonomic response. For example, significant pain or stress could lead to an increase in heart rate, potentially complicating this relationship.