Effects of extracellular calcium on the hair-bundle mechanics in an OHC. (A) Motion of the fixed end of the fiber cemented to the piezoelectric actuator (Δx1, upper), the free end of the fiber attached to the hair bundle (Δx2, middle), and MT current (lower) in 1.5 mM extracellular calcium. (B) Motion of the fixed end of the fiber (Δx1, upper), the end attached to the hair bundle (Δx2, middle), and MT current (lower) in 0.02 mM extracellular calcium. (C, upper) Current-displacement relationships in 1.5 mM calcium (solid circles, prior control; open circles, wash) and in 0.02 mM calcium (crosses). (C, lower) Force-displacement relationships, with symbols the same as in upper. Fast-adaptation time constants (dashed lines): 0.44 ms for 1.5 mM calcium; 1.7 ms for 0.02 mM calcium. Secondary creep in displacement (dashed lines): 0.43 ms, 1.5 mM calcium; 0.70 ms; 0.02 mM calcium. P10 rat, IMAX = 800 pA, KHB = 8 mN·m−1 in 1.5 mM calcium. Stiffness of fiber, 2.4 mN·m−1.