Sal drips some neurotransmitter onto the dendrites of a single neuron. after extensive and careful study, sal determines that the neurotransmitter has no affect of any kind on this neuron. what could best account for the neuron's unresponsiveness?

This is due to inhibitory postsynaptic potential.

Explanation: Inhbitory postsynaptic pontential causes less or no action potential, due to that target nueron recieves negative signals from the transmitter or it has no receptors that can respond to that particular nuerotransmitter as there are many nuerotransmitters varying in sizes and shapes with specificity. Meaning a different nuerotransmitter will generate an electrical impulse to a certain kind of nueron causing an inhibitory/excited response which in this case the response was inhibitory.