Figure 7.
The main line trace shows calcium ion flux for a 3-step increase in voltage. The horizontal axis represents time in milliseconds, and the vertical axis represents membrane potential in millivolts. The graph displays three distinct peaks corresponding to voltage steps at minus 50 millivolts, minus 45 millivolts, and minus 40 millivolts. The inset graphs illustrate three patterns of transient response to two steps of stimulus intensity. Inset a shows classical inactivation, with no response to a second stimulus step. Inset b shows desensitization, with a smaller response to the second stimulus step. Inset c shows ideal increment detection, with responses proportional to the stimulus increment. Each inset graph has the same horizontal axis representing time and vertical axis representing membrane potential.
Increment detection in Rana. Ca2+ flux in response to the three-step increase in voltage shown. Inset, three patterns of transient response to two steps of stimulus intensity (from Meyer and Stryer, 1990): a, “classical” inactivation, if complete, results in no response to a second step; b, desensitization (also known as adaptation), resulting in a smaller response to the second step; c, the ideal increment detection, with responses proportional to stimulus increment. From Pizarro et al. (1997).