The work done by the heart is often compared to that of a pump. This is because our heart also uses ___ to keep
blood flowing through our body.

A) force

B) water

C) levers

D) osmotic pressure

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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nucleic acid molecules are incredibly complex, containing the code that guarantees the four different nucleotide units comprise dna, the nucleic acid of interest to the genealogist. and one of four nitrogen-containing molecules called nucleotides

the titanic would be the correct answer

colors do exist. the color of the sky is actually violet; humans percieve the color of the sky as blue.