Question

You are recording action potentials in a nerve cell in a petri dish in the laboratory. The only difference between your set up in the lab and the normal condition in the body is that the cell is now surrounded by a solution that has a lower concentration of sodium ions than normal. What are you most likely to observe? Group of answer choices The action potentials peak at a higher voltage than in the body There is no difference in the voltage at which the action potentials peak because all action potentials always reach the same voltage The action potentials peak at a lower voltage than in the body

Answer 1

The correct answer is: The action potentials peak at a higher voltage than in the body.

Step-by-step explanation:

Nerve cells in the human body have a very low sodium concentration inside them, while the liquid that surrounds them is rich in this particular ion. When sodium channels in the neuron's plasma membrane are opened, this big difference in sodium concentration -also called gradient- produces a big influx of sodium ions. This rapid entering of Na+ generates a change in the voltage of the cell, because sodium is positively-charged, meaning that the inside of the neuron will become less negative - this is commonly called depolarization of the membrane. Action potentials are generated because of the sudden spike in voltage, but for them to occur, there's a certain voltage that needs to be achieved, so not every depolarization will produce an action potential.

The fact that the cell in the lab is surrounded by a lower concentration of sodium means that the influx of Na+ ions will be lower, because the gradient won't be as big, but also means that the action potential will peak at a higher voltage because the resting membrane potential wasn't as negative to begin with.