Mice with a disrupted β₁(BKβ₁)-subunit of the large-conductance Ca²⁺-activated K⁺ (BK) channel gene develop systemic hypertension and cardiac hypertrophy, which is likely caused by uncoupling of Ca²⁺ sparks to BK channels in arterial smooth muscle cells. However, little is known about the physiological levels of global intracellular Ca²⁺ concentration ([Ca²⁺]_i) and its regulation by Ca²⁺ sparks and BK channel subunits. We utilized a BKβ₁ knockout C57BL/6 mouse model and studied the effects of inhibitors of ryanodine receptor and BK channels on the global [Ca²⁺]_i and diameter of small cerebral arteries pressurized to 60 mmHg. Ryanodine (10 μM) or iberiotoxin (100 nM) increased [Ca²⁺]_i by ∼75 nM and constricted +/+ BKβ₁ wild-type arteries (pressurized to 60 mmHg) with myogenic tone by ∼10 μm. In contrast, ryanodine (10 μM) or iberiotoxin (100 nM) had no significant effect on [Ca²⁺]_i and diameter of −/− BKβ₁-pressurized (60 mmHg) arteries. These results are consistent with the idea that Ca²⁺ sparks in arterial smooth muscle cells limit myogenic tone through activation of BK channels. The activation of BK channels by Ca²⁺ sparks reduces the voltage-dependent Ca²⁺ influx and [Ca²⁺]_i through tonic hyperpolarization. Deletion of BKβ₁ disrupts this negative feedback mechanism, leading to increased arterial tone through an increase in global [Ca²⁺]_i.