READ THIS QUESTION/SCENARIO CAREFULLY:

Extracellular Na+ concentration is higher than intracellular Na+ concentrations. If channels are open up in the membrane of the cell allowing Na+ to cross the membrane (and only Na+), eventually the movement of Na+ into the cell will slow down and may even stop. This is due to the charge (voltage) inside the cell opposing the movement of Na+.

Question

READ THIS QUESTION/SCENARIO CAREFULLY:

Extracellular Na+ concentration is higher than intracellular Na+ concentrations.  If channels are open up in the membrane of the cell allowing Na+ to cross the membrane (and only Na+), eventually the movement of Na+ into the cell will slow down and may even stop.  This is due to the charge (voltage) inside the cell opposing the movement of Na+.

BlackTom AI · Accepted Answer

Question restatement: The scenario describes extracellular Na+ concentration being higher than intracellular Na+ concentration, and Na+ channels opening to allow Na+ to cross the membrane. It claims that the influx of Na+ will slow down or stop because the inside becomes positively charged, opposing further Na+ entry.

First, consider the driving forces for Na+ movement. Na+ tends to move into the cell because its concentration is higher outside than inside, creating a chemical (concentration) gradient. At the same time, as Na+ ions enter, the inside of the cell becomes more positive, creating an electrical (voltage) gradient that opposes further positive charge entry.

As Na+ channels stay open, the net driving force decreases over time as two opposing forces—the decreasing concentration gradient (as Na+ accumulates inside) and the increasing positive membrane potential (which repels additional Na+ ions)—work against continued influx.

This convergence toward a balance point is described by concepts such as the electrochemical gradient and the Nernst/Goldman calculations for Na+. The system will move toward an equilibrium where the electrical and chemical gradients cancel out, at which point net Na+ influx ceases or becomes negligible.

Why this reinforces the statement: The key idea is that initial favorable movement of Na+ into the cell is progressively opposed by the build-up of positive charge inside, which reduces the driving force and can halt net movement if channels remain open long enough.

Why this statement is not incorrect or misleading: It does not claim that Na+ never moves or that there is no driving force; it acknowledges that the driving force weakens due to the opposing voltage inside, which is exactly what happens in real cellular membranes when ions move and charge separation occurs.

In summary, the assertion that inward Na+ flux slows or stops as the inside becomes more positive (opposing further Na+ entry) aligns with fundamental principles of membrane physiology and electrochemical gradients, making the statement true.

BIO 112-Intro. Human Physiology-861, 862, 863 Quiz 2

查看解析

登录即可查看完整答案

类似问题

For a neuron with an initial membrane potential at -70 mV, what would be the result of an increase in the movement of potassium ions out of that neuron's cytoplasm?

Refer to the following graph of an action potential to answer the question. Which Roman numeral in the graph indicates when the neuronal membrane is at its resting potential?

An increase in extracellular K+ concentration can lead to depolarization of the plasma membrane

The inside of a cell is generally more positively charged compared to the outside

The electrochemical gradient across a cell membrane typically favors the influx of sodium ions into the cell

You make a mutation in the Na+/K+ pump such that it now transports 3 K+ ions into the cell instead of two. What will be the consequence of this mutation?

A change in the axon membrane potential from -70 mV to -90 mV would be termed a(n) _____

The difference in electrical charge between the inside and the outside of the axon membrane is defined as the _______ potential.

更多留学生实用工具

考试浏览器助手

风格化写作助手

论文查重助手

文献引用助手

课堂转译助手

课堂笔记助手

Quiz搜索助手

学校历年真题

智能刷题助手

智能匹配练习

希望你的学习变得更简单