Table 2. Sensitivity of firing frequency to independent signals.

Signal	Control value	Δs	FRs (Hz)	Slope (Hz/[s])	SI (%)
Is	0	0.02 nA	2.87	−71.9	100.7
CO2	5%	2%	1.46	0.014	2.09
pHi	7.25	0.1	1.78	−3.5	24.47
pHo	7.45	0.1	2.02	−5.9	41.26

Sensitivity (SI) relative to signal, calculated for different signals. As in Eq (1), it is defined as the percentage of control firing rate (FR_c = 1.43 Hz) to which firing rate increases or decreases in response to a change, Δs, in each signal. Signals: stimulus current (I_s), carbon dioxide level (CO₂), intracellular pH (pH_i), extracellular pH (pH_o).