  We use a hybrid constituent-quark model for the microscopic description of
$\pi N N$, $\pi N \Delta$ and $\pi \Delta \Delta$ vertices. In this model
quarks are confined by an instantaneous potential and are allowed to emit and
absorb a pion, which is also treated as dynamical degree of freedom. The point
form of relativistic quantum mechanics is employed to achieve a
relativistically invariant description of this system. Starting with an $SU(6)$
spin-flavor symmetric wave function for $N_0$ and $\Delta_0$, i.e. the
eigenstates of the pure confinement problem, we calculate the strength of the
$\pi N_0 N_0$, $\pi N_0 \Delta_0$ and $\pi \Delta_0 \Delta_0$ couplings and the
corresponding vertex form factors. Interestingly the ratios of the resulting
couplings resemble strongly those needed in purely hadronic coupled-channel
models, but deviate significantly from the ratios following from SU(6)
spin-flavor symmetry in the non-relativistic constituent-quark model.
