Based on the fluid mosaic model of cell membranes, which of the following statements about membrane phospholipids is true? They frequently leave the bilayer and dissolve in the surrounding solution.
The hydrophilic regions of phospholipids are exposed to the cytosol and extracellular environment.
They occur in an uninterrupted bilayer, with membrane proteins restricted to the surface of the membrane.
They frequently flip-flop from one side of the membrane to the other.

b. regulated is the actual answer to your question.

explanation:

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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it’s lava came from an explosive eruption