If, and only blood sugar levels rise past a certain point, the cells will release a hormone called insulin. Insulin acts as a/an in a homeostatic feedback loop

When blood glucose level rises beyond the threshold levels, the pancreas secrets hormones insulin. The latter ensures entry of  glucose into the cells through Glut transporters for cellular utilization, therefore reducing the blood levels., and promotes storage as glycogen in the liver and muscles.  

How ever if  the glucose levels drops below the  set point, an hormone glucagon is also produce by the pancreas to cause the liver o withdrawal and breakdown glucose storage as  glycogen back to glucose thus raising the blood glucose level back to the normal levels.

This is an example of negative feedback mechanism, because the increase in the input levels (blood glucose levels) brings about a counter  mechanisms (insulin secretions)as output , to reduce the  elevated   levels by promoting  entry into the cells,, thus bringing the levels to threshold levels.

Thus insulin is acting in a negative feedback mechanism to control blood glucose levels

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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explanation:

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