Consider Neuron B in the frog central nervous system whose plasma membrane has a previously unknown channel that is selectively conductive to a newly discovered tetravalent anion named TETRAVA with a valence of -4.
The threshold for an action potential in Neuron B is -55 millivolts and the resting potential for Neuron B is - 70 millivolts. The TETRAVA channel in Neuron B is part of an ionotropic receptor with an extracellular binding site for the newly discovered ligand LGD. When LGD binds to its binding site, there is an increase in the TETRAVA conductance of Neuron B. Neuron A synapses onto Neuron B. Neuron A's neurotransmitter is LGD.
A. The extracellular concentration of TETRAVA is 100,000 times greater than the intracellular concentration of TETRAVA. In response to an action potential in Neuron A, there will be an increase in the membrane voltage of Neuron B.
B. The extracellular concentration of TETRAVA is 10,000 times greater than the intracellular concentration of TETRAVA. In response to an action potential in Neuron A, there will be an increase in the amount of intracellular TETRAVA in Neuron B.
C. The extracellular concentration of TETRAVA is 1,000 times greater than the intracellular concentration of TETRAVA. In response to an action potential in Neuron A, there will be an excitatory postsynaptic potential in Neuron B.
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