  Polarized parton distributions and structure functions of the nucleon are
analyzed in the improved valon model. The valon representation provides a model
to represent hadrons in terms of quarks, providing a unified description of
bound state and scattering properties of hadrons. Polarized valon distributions
are seen to play an important role in describing the spin dependence of parton
distributions in the leading order (LO) and next-to-leading order (NLO)
approximations. In the polarized case, a convolution integral is derived in the
framework of the valon model. The Polarized valon distribution in a proton and
the polarized parton distributions inside the valon are necessary to obtain the
polarized parton distributions in a proton. Bernstein polynomial averages are
used to extract the unknown parameters of the polarized valon distributions by
fitting to the available experimental data. The predictions for the NLO
calculations of the polarized parton distributions and proton structure
functions are compared with the LO approximation. It is shown that the results
of the calculations for the proton structure function, $xg_1^p$, and its first
moment, $\Gamma_{1}^p$, are in good agreement with the experimental data for a
range of values of $Q^{2}$. Finally the spin contribution of the valons to the
proton is calculated.
