  The electroweak response functions for inclusive electron scattering are
calculated in the Relativistic Fermi Gas model, both in the quasi-elastic and
in the $\Delta$ peak regions. The impact of relativistic kinematics at high
momentum transfer is investigated through an expansion in the initial nucleonic
momentum, which is however exact in the four-momentum of the exchanged boson.
The same expansion is applied to the meson exchange currents in the
particle-hole sector: it is shown that the non-relativistic currents can be
corrected by simple kinematical factors to account for relativity. The
left-right asymmetry measured via polarized electron scattering is finally
evaluated in the quasi-elastic and $\Delta$ peaks.
