QUESTION 15 Which of the following statements applies best to the term 'receptor reserve?

Receptor reserve is determined by the number of receptors that are required to be occupied by agonist to initiate a
maximal response compared to the total number of cell-surface receptors.
Receptor reserve, also known as 'spare receptors', occurs when the Kd for agonist binding to the receptor is smaller
than the EC50 determined for a particular physiological response.
Receptor reserve is a useful pharmacological parameter, as it is specific to a particular cell-type.
Receptor reserve refers to the pool of intracellular receptors that are able to translocate to the plasma membrane.

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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