  We report a doping dependant Electronic Raman Scattering (ERS) study of
HgBa$_2$CuO$_{4+\delta}$ (Hg-1201) single crystals. We investigate the dynamics
of the antinodal and nodal quasiparticles. We show that the dynamical response
of the antinodal quasiparticles is strongly reduced towards the underdoped
regime in both the normal and superconducting states. When probing the nodal
quasiparticles, we are able to distinguish between the energy scale of the
pseudogap and that of the superconducting gap. A simple model relating the
suppression of the dynamical response of the antinodal quasiparticles to
fluctuations related to a competing phase is proposed.
