Question

Pufferfish (Fugu) are a delicacy in Japan, but must be cleaned very carefully as their liver contains tetrodotoxin which blocks voltage-gated Na+ channels. Imagine you are testing for the presence of this toxin using a neuron in a dish. You apply an electrical stimulus to the neuron that should produce an action potential. What will you observe if tetrodotoxin levels are high enough to block the neuron's voltage-gated Na+ channels?
a. The neuron will exhibit a slow depolarization even before the stimulus is applied, followed by a normal action potential.
b. The neuron will exhibit a slow hyperpolarization even before the stimulus is applied.
c. The neuron will show a normal resting potential, but will not exhibit depolarization when the stimulus is applied.
d. The neuron will exhibit rapid depolarization, but will not repolarize.
e. The neuron will depolarize normally, but then become hyperpolarized such that the membrane potential is much lower than usual.

Answer 1

Answer:

Option (C).

Explanation:

Membrane potential may be defined as the difference in the electric potential of the inside and outside of the cell. The resting membrane potential of neuronal cell is -70mV.

Pufferfish contains tetrodotoxin that blocks the voltage gated sodium channels. The movement of sodium ions inside the cell causes the depolarization of cell and makes the cell membrane potential towards more positive. This tetrodotoxin causes the normal resting potential but the cell are not able to depolarize if the stimulus is given to the cell.

Thus, the correct answer is option (c).