Cerebral autoregulation is achieved via myogenic response to pressure changes and metabolic factors (CO2, pH) modulating local vessel tone; NO contributes.

• A. Autoregulation relies only on heart rate
• B. NO causes vasoconstriction that dominates
• C. Myogenic response and CO2/pH modulation; NO contributes
• D. Autoregulation controlled by sympathetic nervous system alone

Answer: (C)

Cerebral autoregulation hinges on vessel-level control that keeps blood flow steady as blood pressure changes. The myogenic response of smooth muscle reacts to pressure shifts by constricting when pressure rises and relaxing when it falls, helping stabilize flow. Local metabolic signals, especially CO2 and pH, fine-tune vessel tone: higher CO2 or lower pH promote vasodilation to meet metabolic needs, while lower CO2 or higher pH can promote constriction. NO from the endothelium adds a vasodilatory influence, helping to modulate tone rather than driving it alone. This combined mechanism contrasts with ideas that rely solely on heart rate or sympathetic control, which are not the primary drivers of cerebral autoregulation in healthy conditions.