Respiratory effects [edit]. The PRG antagonizes the apneustic center, cyclically inhibiting inhalation. The PRG limits the burst of action potentials in the phrenic nerve, effectively decreasing the tidal volume and regulating the respiratory rate.espiratory effects [edit]. The PRG antagonizes the apneustic center, cyclically inhibiting inhalation. The PRG limits the burst of action potentials in the phrenic nerve, effectively decreasing the tidal volume and regulating the respiratory rate.
Because the ones at the bottom, the animals would have died first and soil would have covered them building a cliff and the fossils up top would have died later. 3 people found this useful.
Geogolists know the age of certain fossils, which are known as 'index fossils'. When they find these index fossils in certain rock layers, they know the age of the rock layers. sedimentary rock cant be dated with radioactivity because it is a mixture of many different rocks. but there are certain layers that can be radioactively dated. fossils are used for the layers in between.