What separates insects from other groups of invertebrates?

Scientists group invertebrates into eight major phyla, including sponges, cnidarians, worms, mollusks, echinoderms, and arthropods. Many invertebrate phyla may be divided into more than one class

not sure if this is correct

the answer that best describes the relative refractory period in the neuron is the resting membrane potential is restored, but concentrations of sodium and potassium are not restored to their original state.

the refractory period is the time during which another stimulus given to the neuron will not lead to a second potential. thus, because na+ channels are inactivated during this time, additional depolarizing stimuli do not lead to new action potentials.  

read more on -

find out why you don't need to aim at such a syllable pattern in english. you may have thought that haiku was supposed to be 5-7-5, so what's up with the logo by the gravitational pull of celestial objects, can touch us in unexpected ways.