Figure 2. Total ionic currents for 
fixed as a function of 
without (left) and with calcium channels (right).
Blank portions corresponds to the values of 
where 
, shaded portions corresponds to the values of 
where 
, and the dashed lines correspond to the values of 
where 
. The hyperpolarizing calcium pump current 
accounts for the vertical shift of the curve in the right figure. Note that the total ionic currents monotonically increase only in the absence of calcium channels (left).