Certain species of frogs in the genus Phyllobates have a powerful defensive adaptation—their skin can secrete a milky fluid that contains an extremely toxic compound called batrachotoxin (BTX). These frogs, which are found in Colombia, are known as poison dart frogs because some indigenous Colombian hunters coat the tips of their blowgun darts with the frogs' skin secretions. An animal hit by one of these darts dies quickly. What is the mechanism of action of BTX? Predict the effects of each of the following on the membrane potential of a neuron simultaneously poisoned with BTX: (a) removing extracellular sodium ions; (b) increasing the intracellular potassium ion concentration; and (c) adding tetrodotoxin from puffer fish.

Verified step by step guidance

1. Step 1: Understand the mechanism of action of batrachotoxin (BTX). BTX works by binding to voltage-gated sodium channels in the neurons, causing them to remain open. This allows sodium ions to continuously flow into the neuron, leading to a continuous depolarization and preventing the neuron from repolarizing. This results in the continuous firing of action potentials, leading to muscle contractions and potentially death.
2. Step 2: Predict the effect of removing extracellular sodium ions. If extracellular sodium ions are removed, the gradient that drives the influx of sodium ions into the neuron would be eliminated. This would reduce the depolarization caused by BTX, as there would be fewer sodium ions to enter the neuron. However, the neuron would still be unable to repolarize due to the continuous opening of the sodium channels by BTX.
3. Step 3: Predict the effect of increasing the intracellular potassium ion concentration. Increasing the intracellular potassium ion concentration would increase the gradient that drives the efflux of potassium ions from the neuron. This could potentially counteract the depolarization caused by BTX by making the inside of the neuron more negative. However, the neuron would still be unable to repolarize due to the continuous opening of the sodium channels by BTX.
4. Step 4: Predict the effect of adding tetrodotoxin from puffer fish. Tetrodotoxin works by blocking voltage-gated sodium channels, preventing sodium ions from entering the neuron. If tetrodotoxin is added, it could potentially counteract the effects of BTX by blocking the sodium channels that BTX keeps open. This would prevent the continuous influx of sodium ions and allow the neuron to repolarize.
5. Step 5: Summarize the predictions. Removing extracellular sodium ions and increasing the intracellular potassium ion concentration could potentially reduce the depolarization caused by BTX, but the neuron would still be unable to repolarize due to the continuous opening of the sodium channels by BTX. Adding tetrodotoxin could potentially counteract the effects of BTX by blocking the sodium channels that BTX keeps open, allowing the neuron to repolarize.