Question

Cerebral blood flow is regulated by all except:

• A. Blood pressure
• B. Arterial PCO₂
• C. Potassium ions
• D. A & C

Answer 1

The Correct Option is D

The regulation of cerebral blood flow is a critical physiological process influenced by various factors. Among the listed options:

• Blood pressure: Cerebral blood flow is regulated by mechanisms such as autoregulation, which maintains a consistent blood flow despite changes in systemic blood pressure. Therefore, blood pressure is indeed a regulator of cerebral blood flow.
• Arterial PCO₂: Levels of carbon dioxide in the blood play a pivotal role in the regulation of cerebral blood flow. An increase in arterial PCO₂ leads to vasodilation and increased blood flow, while a decrease causes vasoconstriction and reduced flow. Thus, arterial PCO₂ is a regulator.
• Potassium ions: Potassium ions influence various cellular functions but are not primary regulators of cerebral blood flow.
• A & C: This option suggests that blood pressure and potassium ions are not regulators. Since potassium ions are not directly involved, this option is correct as both A (blood pressure) and C (potassium ions) are not the ones left from the regulatory factors mentioned.

The correct choice is: A & C, as blood pressure and potassium ions are either regulated by other processes or are not primary regulators of cerebral blood flow.