  We study the long range part of the $\Lambda$-hyperon optical potential in
nuclei using Quantum Many Body techniques and flavor-SU(3) Chiral Lagrangians
as starting point. More precisely, we study the contributions to the
$\Lambda$-hyperon optical potential due to the long-range two-pion exchange,
with $\Sigma$ and $\Sigma^*$ baryons in the internal baryonic lines and
considering Nh and $\Delta$h excitations. We also consider the contribution to
the spin-orbit potentials that comes out from these terms. Our results support
a natural explanation of the smallness of the $\Lambda$-nuclear spin-orbit
interaction and shows the importance of the $\Sigma^*$ and $\Delta$ degrees of
freedom for the hyperon-nucleus interactions.
