What are advantages of positive feedback? if
there any, what are they, if no then reason?

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.  

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several tissues working together form an organ, and several organs together make up an organisms.

the group of cell that carries out special jobs are tissue.

answerparathyroid gland;