  This paper presents an update to the MK model, which was developed to
describe single pion production in neutrino-nucleon interactions. Originally
the MK model used the helicity amplitudes and the hadronic current form-factors
of the Rein and Sehgal model. The update includes a new definition for the
helicity amplitudes in the first and second resonance regions, and new
vector-current form factors. Fits to electron-proton scattering data were used
to determine these vector-current form factors, and to assign errors to the
constrained free parameters of the model.
