A mathematical description of the refractoriness period 
in neuronal diffusion modeling is given and its  moments  
are explicitly  obtained in a form that is suitable 
for quantitative evaluations. Then, for the Wiener, 
Ornstein-Uhlenbeck and Feller neuronal models, 
an analysis of the features exhibited by the mean and 
variance of the first passage time and of refractoriness 
period is performed.