Why must a normal animal respond to the sight and sound of a beast of prey?

Many deep ocean creatures depend on antennae to sense the world around them since light doesn't reach those depths to allow for any form of sight. This antennae senses nearby movement, such as that created by food-sources or potential mates, allowing for the creature to "live a normal life" without the ability to see.

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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one is through turgidity. this occurs before ground tissue ( collenchyma

and sclerenchyma cells) become well

developed to give structural support to the plant as it grows bigger. the xylem

tissue (composed of rigid tissue) of the young

plant render this support and also maintaining osmotic turgidity of the surrounding

plant cells.