In which specimen were cells first identified

The specimen where cells were first identified was cork. Robert Hooke was examining a piece of cork using a microscope in 1665.

cork (thin slices of cork)

Explanation:

Robert Hooke used the term "cell" in 1665. He made the first compound microscope, and he used it to see the cork cells. He took thin slices of cork and examined it under the compound microscope. He found smaller compartments in it. These compartments were arranged like a honeycomb structure. The cork was a dead plant part, hence inside of each compartment was empty.  He called the outer wall is the cell wall.

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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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