What is ischemia?

Ischemia refers specifically to a condition characterized by inadequate arterial blood flow to a particular tissue or organ, resulting in a deficiency of oxygen and nutrients necessary for cellular metabolism. This reduced blood supply can lead to tissue damage or dysfunction if not resolved, as cells begin to suffer from a lack of oxygen (hypoxia) and can eventually undergo necrosis if ischemia persists. The underlying causes of ischemia can include conditions such as atherosclerosis, thrombosis, or embolism, which obstruct normal blood flow.

The other options describe conditions that do not align with the definition of ischemia. Excessive blood flow to the brain indicates hyperemia rather than ischemia. High levels of carbon dioxide in the blood pertain to respiratory or metabolic issues, which are unrelated to ischemic processes. Excessive pressure within the cranial cavity could refer to conditions such as intracranial hypertension, but again, this is distinct from ischemia since it does not specifically address inadequate blood flow.