Synaptic Transmission – NROSCI 1017 – Spring 2025
突触传递 - NROSCI 1017 - 2025 年春

Worksheet assignment – Unit 1 (resting membrane potential and driving force)
工作表作业 - 第 1 单元（静息膜电位和驱动力）

This assignment is designed to help you understand concepts related to Unit 1 including driving force, membrane potential and Ohm’s law. First you will experiment with how ion concentrations in extracellular fluid affect the membrane potential (V_m) of a neuron. Second, you will answer multiple choice questions on these topics. Third, you will generate a plot of the driving force on Na⁺ and K⁺ as a function of V_m.
本作业旨在帮助您理解与第一单元相关的概念，包括驱动力、膜电位和欧姆定律。首先，您将实验细胞外液中的离子浓度如何影响神经元的膜电位（V _m ）。其次，回答有关这些主题的多项选择题。第三，您将绘制 Na ⁺ 和 K ⁺ 的驱动力与 V _m 的函数关系图。

There are very specific and detailed instructions on this worksheet and on Canvas- *please* read and follow them for full credit!!
本工作表和 Canvas 上有非常具体和详细的说明--*请阅读并遵守，以获得满分

NOTE: YOUR WORK ON THIS ASSIGNMENT MUST BE UPLOADED TO CANVAS AS A PDF FILE NO LATER THAN 11:59 PM ON Tuesday, Jan. 30^th.
注意：您的作业必须在 1 月 30 日（星期二）晚上 11:59 之前以 PDF 文件的形式上传至 CANVAS ^th 。

THERE WILL BE NO EXCEPTIONS TO THIS DEADLINE, AND THERE ARE NO EXTRA CREDIT OR MAKE-UP ASSIGNMENTS.
在此截止日期前，不得有任何例外，也没有额外学分或补做作业。

Assignment 1, part 1: Effects of ion concentration on membrane potential
作业 1，第 1 部分：离子浓度对膜电位的影响

Instructions:
说明：

The first part of this assignment utilizes a neuron simulation program developed by Dr. Hillel Chiel in the Department of Biology at Case Western Reserve University. The link for the relevant neuron simulation is:
作业的第一部分使用了凯斯西储大学生物系 Hillel Chiel 博士开发的神经元模拟程序。相关神经元模拟程序的链接是

https://neurowiki.case.edu/JSNeuroSim/simulations/nernstpassivemembrane_jqplot.html

You must copy and paste the link into your browser (clicking it here won’t work!)
您必须将链接复制并粘贴到浏览器中（点击此处无效！）。

Step 1: Setting up and understanding the simulation Open the simulation link, which brings you to a page entitled, “Nernst passive membrane simulation”. On the left side of the page are three categories of values that can be set according to what is being tested and recorded in the simulated experiment. I refer to these initial values here as the Default Simulation Values. They are pre-set by the simulation and can be restored by clicking on the “Reset” button at the bottom of the simulation page. For this assignment, most of these values will not be altered; in fact, the only values you will change are in the top category, “Cell Properties”.
步骤 1：设置和了解模拟 打开模拟链接，进入 "Nernst 被动膜模拟 "页面。页面左侧有三类数值，可根据模拟实验中测试和记录的内容进行设置。我在这里将这些初始值称为 "默认模拟值"。它们由模拟预先设置，点击模拟页面底部的 "重置 "按钮即可恢复。在本次作业中，这些值中的大部分都不会被修改；事实上，你要修改的唯一值就在最上面的 "细胞属性 "类别中。

The values in this category that you will be altering for this assignment are the Na⁺, K⁺, and Cl^- conductances and the Na⁺, K⁺, and Cl^- Nernst potentials. Note that “Nernst potential” is just another term for the equilibrium potential/reversal potential of an ion.
在本作业中，您需要更改的数值包括 Na ⁺ 、K ⁺ 和 Cl ^- 电导以及 Na ⁺ 、K ⁺ 和 Cl ^- Nernst 电位。请注意，"Nernst 电位 "只是离子平衡电位/反转电位的另一个术语。

On the right side of the page is a series of graphs. The Stimulation Current graph shows the time points at which current is being injected into the simulated neuron through a microelectrode (this is referred to as a
页面右侧是一系列图表。刺激电流图显示了通过微电极向模拟神经元注入电流的时间点（这被称为

“stimulus”), and the Membrane Current graph shows how the current for each ion changes when this occurs. You don’t need to measure anything from these two graphs to do the assignment, but that’s what they are, in case you are interested.
刺激"），而 "膜电流 "图显示了发生这种情况时每种离子的电流是如何变化的。您不需要从这两幅图中测量任何东西来完成作业，但如果您感兴趣的话，这就是它们的作用。

For this assignment, you will only be making measurements from the top graph (Membrane Potential vs. Time). This graph indicates how the membrane potential changes in response to injecting current into the neuron. In order to accurately read values from this graph, hover your cursor over the graph and a gray box will appear that gives the time (in ms) where the cursor is along the x-axis, and membrane potential values (in mV) for the membrane potential at that time point. You will use the values in this box to collect data from the graph for this assignment. Using this means you do not need to zoom in on the graph each time a measurement is to be made; you can just read the value(s) from this gray box. Note: if the gray box doesn’t appear when you hover your cursor over the graph, just click on the white space outside the graph, and then try hovering over the graph again.
在本次作业中，您将只对顶图（膜电位与时间关系）进行测量。该图显示向神经元注入电流时膜电位的变化情况。为了准确读取该图中的数值，请将光标悬停在该图上，这时会出现一个灰色方框，显示光标沿 x 轴所在的时间（毫秒）和该时间点的膜电位值（毫伏）。您将使用该方框中的值从图表中收集数据来完成本次作业。这意味着每次测量时，您无需放大图表；您只需读取灰色框中的值即可。注意：如果将光标悬停在图形上时没有出现灰色框，只需单击图形外的空白处，然后再试着将光标悬停在图形上。

Look at the resting V_m, before any stimuli are given. The first stimulus begins at 10 ms, so hover your cursor over the graph before this (i.e. between 0-10 ms) and read the V_m value. This is the membrane potential before any stimulation is provided (so, this is V_rest) using the default simulation values. If the value is not -75.469 mV, click the “Reset” button in the lower left of the page. This will reset to the default simulation values and re-run the experiment.
查看静态 V _m ，然后再给予任何刺激。第一次刺激开始于 10 毫秒，因此将光标悬停在图表之前（即 0-10 毫秒之间），读取 V _m 值。这是提供任何刺激之前的膜电位（因此，这是 V _rest ），使用默认模拟值。如果该值不是 -75.469 mV，请单击页面左下方的 "重置 "按钮。这将重置为默认模拟值并重新运行实验。

Step 2: (to answer questions 1 and 2)
步骤 2：（回答问题 1 和 2）

Next, change the K⁺ Nernst potential (E_K; default value = -80 mV) to a value at which V_rest = -60.0 mV. You will have to try different values for E_K and see what happens to the V_rest value until you find the right value for E_K. Don’t change any other cell properties – just E_K. Be sure to click “Run” to see the results for a given value.
接下来，将 K ⁺ Nernst 电位（E _K ；默认值 = -80 mV）改为 V _rest = -60.0 mV 的值。您需要尝试不同的 E _K 值，并查看 V _rest 值的变化情况，直到找到合适的 E _K 值。不要更改任何其他单元格属性，只更改 E _K 。请务必点击 "运行 "查看给定值的结果。

Question 1: What value of E_K causes V_rest to equal -60 mV? Note that the E_K values do not need to be integers (e.g. you can type in decimal values such as -29.5 mV). Enter the answer on the Unit 1 assignment answer submission page.
问题 1：E _K 的什么值会导致 V _rest 等于 -60 mV？请注意，E _K 值不必是整数（例如，您可以输入十进制值，如 -29.5 mV）。将答案输入第 1 单元作业答案提交页面。

Question 2: Why does changing E_K move V_rest in this direction (i.e. relative to the default V_rest = -75.469 mV)? Keep in mind that when a neuron is not being stimulated (i.e. is “at rest”), some K⁺ channels are always open (these K⁺ channels are “leak” channels not voltage-gated). Enter the answer on the Unit 1 assignment answer submission page.
问题 2：为什么改变 E _K 会使 V _rest 朝这个方向移动（即相对于默认的 V _rest = -75.469 mV）？请记住，当神经元没有受到刺激时（即处于 "静止 "状态），一些 K ⁺ 通道总是开放的（这些 K ⁺ 通道是 "泄漏 "通道，而不是电压门控通道）。请在第 1 单元作业答案提交页面输入答案。

This occurs because a more depolarized E_K decreases the number of K⁺ ions that go down the K⁺ concentration gradient, which depolarizes V_rest.
这是因为去极化程度较高的 E _K 会减少沿 K ⁺ 浓度梯度向下移动的 K ⁺ 离子的数量，从而使 V _rest 去极化。

This occurs because a more depolarized E_K increases the number of K⁺ ions that go down the K⁺ concentration gradient, which depolarizes V_rest.
这是因为去极化程度较高的 E _K 会增加沿 K ⁺ 浓度梯度向下移动的 K ⁺ 离子的数量，从而使 V _rest 去极化。

This occurs because a more hyperpolarized E_K decreases the number of K⁺ ions that go down the K⁺ concentration gradient, which depolarizes V_rest.
出现这种情况是因为超极化 E _K 会减少沿 K ⁺ 浓度梯度向下移动的 K ⁺ 离子的数量，从而使 V _rest 去极化。

This occurs because a more hyperpolarized E_K increases the number of K⁺ ions that go down the K⁺ concentration gradient, which depolarizes V_rest.
这是因为超极化 E _K 增加了沿 K ⁺ 浓度梯度向下移动的 K ⁺ 离子的数量，从而使 V _rest 去极化。

Step 3: (to answer questions 3 and 4)
步骤 3：（回答问题 3 和 4）

Next, set the values of the variables back to the default simulation settings by clicking “Reset” in the lower left part of the page. Then set the Membrane potassium conductance value from the default of 3 µS to 0.3 µS and click the “Run” button. This is equivalent to closing a portion of those K⁺ channels that are usually open at rest. V_rest should now be -51.0 mV.
接下来，点击页面左下方的 "Reset（重置）"，将变量值设置回默认模拟设置。然后将膜钾电导值从默认的 3 µS 设置为 0.3 µS，点击 "运行 "按钮。这相当于关闭了部分通常在静态时开放的 K ⁺ 通道。V _rest 现在应为 -51.0 mV。

Now, with the Membrane potassium conductance value still set at 0.3 µS, find a value for the Potassium Nernst potential that causes V_rest = -60 mV.
现在，在膜钾电导值仍为 0.3 µS 的情况下，找出一个能使 V _rest = -60 mV 的诺氏钾电位值。

Question 3: What value of E_K causes V_rest to equal -60 mV now that the K⁺ conductance = 0.3 µS? Enter the answer on the Unit 1 assignment answer submission page.
问题 3：在 K ⁺ 电导 = 0.3 µS 的情况下，E _K 的什么值会导致 V _rest 等于 -60 mV？请在第 1 单元作业答案提交页面输入答案。

Question 4: Why does lowering the K⁺ conductance (to 0.3 µS) alter the E_K value required for V_rest to = -60 mV, compared to when the K⁺ conductance was the default value of 3 µS? Enter the answer on the Unit 1 assignment answer submission page.
问题 4：与 K ⁺ 电导为默认值 3 µS 时相比，为什么降低 K ⁺ 电导（至 0.3 µS）会改变 V _rest = -60 mV 所需的 E _K 值？请在第 1 单元作业答案提交页面输入答案。

Now that there are fewer K⁺ channels open, the current going through the remaining channels has more of an effect on V_rest. So, the E_K value required to move V_rest to -60.0 mV must be more negative than when the K⁺ conductance was 3 µS.
现在打开的 K ⁺ 通道减少了，通过剩余通道的电流对 V _rest 的影响更大。因此，将 V _rest 移至 -60.0 mV 所需的 E _K 值必须比 K ⁺ 电导为 3 µS 时更负。

Now that there are fewer K⁺ channels open, the current going through the remaining channels has more of an effect on V_rest. So, the E_K value required to move V_rest to -60.0 mV must be more positive than when the K⁺ conductance was 3 µS.
现在开放的 K ⁺ 通道减少了，通过剩余通道的电流对 V _rest 的影响更大。因此，将 V _rest 移至 -60.0 mV 所需的 E _K 值必须比 K ⁺ 电导为 3 µS 时更正。

Now that there are fewer K⁺ channels open, the current going through the remaining channels has less of an effect on V_rest So, the E_K value required to move V_rest to -60.0 mV must be more negative than when the K⁺ conductance was 3 µS.
现在，打开的 K ⁺ 通道减少了，通过剩余通道的电流对 V _rest 的影响也就更小了。因此，将 V _rest 移至 -60.0 mV 所需的 E _K 值必须比 K ⁺ 电导为 3 µS 时更负。

Now that there are fewer K⁺ channels open, the current going through the remaining channels has less of an effect on V_rest. So, the E_K value required to move V_rest to -60.0 mV must be more positive than when the K⁺ conductance was 3 µS.
现在开放的 K ⁺ 通道减少了，通过剩余通道的电流对 V _rest 的影响也就更小了。因此，将 V _rest 移至 -60.0 mV 所需的 E _K 值必须比 K ⁺ 电导为 3 µS 时更正。

Assignment 1, part 2: Driving force and membrane potential.
作业 1 第 2 部分：驱动力和膜电位。

Part 2 consists of 2 multiple choice questions. Submit your answers on the Unit 1 assignment answer submission page.
第 2 部分包括 2 道选择题。请将答案提交到第 1 单元作业答案提交页面。

Question 5:
问题 5：

Identify the point in the action potential where the driving force for sodium is the greatest. Why?
找出钠驱动力最大的动作电位点。为什么？

A; The driving force for Na is greatest right before the AP because voltage-gated sodium channels are beginning to open.
A；由于电压门控钠通道开始开放，因此在 AP 之前 Na 的驱动力最大。

B; The driving force for Na is greatest during the upstroke because sodium conductance is highest (i.e. most sodium channels are open).
B；上冲时 Na 的驱动力最大，因为钠传导性最高（即大多数钠通道处于开放状态）。

C; The driving force for Na is greatest at the peak of the AP because this is when the cell membrane is the most depolarized.
C；AP 峰值时 Na 的驱动力最大，因为此时细胞膜的去极化程度最高。

D; The driving force for Na is greatest during the afterhyperpolarization because that is when V_m and E_Na are farthest apart.
D；Na 的驱动力在过极化后最大，因为此时 V _m 和 E _Na 相距最远。

The driving force is consistent throughout the action potential because it depends only on the sodium concentration gradient and not on the membrane potential.
驱动力在整个动作电位中都是一致的，因为它只取决于钠浓度梯度，而不取决于膜电位。

Question 6:
问题 6：

During each current step, we can record fluctuations in the membrane potential. A positive current injection of 25 pA raises the membrane potential from -70 mV to -66 mV (a 4mV change). Now consider the situation where the same amount of current (25 pA) is injected into a neuron with a diameter that is only half that of the original cell. How would the membrane potential change induced by the current differ in this new smaller neuron?
在每个电流步骤中，我们都能记录膜电位的波动。注入 25 pA 的正向电流会使膜电位从 -70 mV 上升到 -66 mV（4mV 的变化）。现在考虑这样一种情况：向直径只有原来细胞一半的神经元注入相同的电流（25 pA）。在这个新的更小的神经元中，电流引起的膜电位变化会有什么不同？

a) the membrane potential change would be larger than 4mV because the smaller neuron has greater resistance.
a) 膜电位变化将大于 4mV，因为较小的神经元具有更大的电阻。

b) the membrane potential change would be smaller than 4mV because the smaller neuron has greater resistance.
b) 膜电位变化将小于 4mV，因为较小的神经元具有更大的电阻。

c) the membrane potential change would be larger than 4mV because the smaller neuron has less resistance
c) 膜电位变化将大于 4mV，因为较小的神经元阻力较小

d) the membrane potential change would be smaller than 4mV because the smaller neuron has less resistance.
d) 膜电位变化将小于 4mV，因为较小的神经元阻力较小。

e) The membrane potential change would not be significantly different from 4mV because the current amplitude is the same.
e) 由于电流幅度相同，膜电位变化与 4mV 不会有明显差异。

Assignment 1, part 3
作业 1，第 3 部分

The goal for this part of the assignment is to make a plot of the driving force on Na⁺ and K⁺, as a function of V_m. This part of the assignment does not utilize the simulation used in part 1. Instead, you will perform some very simple calculations using the equation DF = (V_m – E_qion).
这部分作业的目标是绘制 Na ⁺ 和 K ⁺ 的驱动力与 V _m 的函数关系图。这部分作业不使用第 1 部分中的模拟。相反，您将使用公式 DF = (V _m - E _qion ) 进行一些非常简单的计算。

For this part of the assignment, you will need to record your “data” in a spreadsheet and then plot them. Standard spreadsheet programs with these capabilities (e.g. Excel) or online plotting programs (e.g. desmos
在这部分作业中，您需要在电子表格中记录 "数据"，然后绘制它们。具有这些功能的标准电子表格程序（如 Excel）或在线绘图程序（如 desmos

https://www.desmos.com) are sufficient. Both lines (one for Na⁺ and one for K⁺ may be plotted on the same plot or on separate plots. You will then submit a PDF file containing your plot(s) (with correct axis labels), your table of values, and your name. See below for more detailed instructions about how to do this.
https://www.desmos.com）即可。两条线（一条是 Na ⁺ 线，另一条是 K ⁺ 线）可以绘制在同一幅图上，也可以绘制在不同的图上。然后，您将提交一份 PDF 文件，其中包含您绘制的曲线图（带有正确的坐标轴标签）、数值表和您的姓名。有关如何操作的详细说明，请参阅下文。

Instructions for making plot(s):
制作地块的说明：

To make the plot(s), calculate the driving force (DF) as a function of V_m, at values from -80 mV to +60 mV, in 20 mV increments (-80 mV, -60 mV, -40 mV, etc.). For this assignment, assume E_K = -70 mV and E_Na = +55 mV. These are not the precise values we used in class for these equilibrium potentials, but they are not out of the range of normal, depending on the neuron being studied.
要绘制曲线图，请计算驱动力 (DF) 与 V _m 的函数关系，数值从 -80 mV 到 +60 mV，以 20 mV 为增量（-80 mV、-60 mV、-40 mV 等）。在本作业中，假设 E _K = -70 mV 和 E _Na = +55 mV。这并不是我们在课堂上使用的这些平衡电位的精确值，但根据所研究的神经元，它们并没有超出正常范围。

Once you have calculated the values, plot them with V_m along the x-axis and DF along the y-axis. Label both axes with the type of value for each of the axes (that is, what is being measured, e.g. V_m) and the correct units for that axis (e.g. mV). So, using these examples, this entire label would read: V_m (mV). Limit your axes to the relevant ranges (Vm = -80 mV to +60 mV and the relevant DF values)
计算出数值后，将 V _m 沿 x 轴绘制，DF 沿 y 轴绘制。在两个轴上分别标上数值类型（即测量的内容，如 V _m ）和该轴的正确单位（如 mV）。因此，使用这些示例，整个标签应为V _m (mV).将坐标轴限制在相关范围内（Vm = -80 mV 至 +60 mV 以及相关的 DF 值）

Rubric for grading plot and table:
情节和表格评分标准：

Correct axis labels – you must put these labels on the plot(s) and include the type of value for each of the axes (that is, what is being measured, e.g. V_m) and the correct units for that axis (e.g. mV). So, using these examples, this entire label would read: V_m (mV). (1 point) Correct values/line for Na⁺ (1 point)
正确的坐标轴标签 - 您必须在图表上标注这些标签，并包括每个坐标轴的数值类型（即测量的内容，如 V _m ）和该坐标轴的正确单位（如 mV）。因此，使用这些示例，整个标签应为V _m (mV)。(1 分) Na ⁺ 的正确值/行 (1 分)

Correct values/line for K⁺ (1 point)
K ⁺ 的正确值/行（1 分）

TO SUBMIT FOR PART 3 OF THE ASSIGNMENT:
以提交作业的第 3 部分：

Put an image of the plot(s) you generate in a Word document or other document you can save as a PDF. This can be done either by copying the plot from the program you use or just taking a screenshot of the plot and pasting it into Word or similar.
将生成的绘图图像放入 Word 文档或其他可以保存为 PDF 格式的文档中。这可以通过从您使用的程序中复制绘图，或者直接截取绘图截图并粘贴到 Word 或类似文档中来实现。

Also include on the document the table of values you made (again, pasting directly or using a screenshot of the graph.
同时在文档中包含您制作的数值表（同样，可以直接粘贴或使用图表截图）。

INCLUDE YOUR NAME ON THE PDF FILE on the page itself (just type it on so it’s visible when the document is opened as a PDF).
在 PDF 文件的页面上注明您的姓名（只需打上您的姓名，以便在打开 PDF 文件时可以看到）。

Include your initials in the filename.
在文件名中包含您姓名的首字母缩写。

Save your PDF and upload for Question 7 on the Unit 1 assignment answer submission page. Do NOT send or upload a link to an online document. You must upload a PDF file to this answer submission page.
保存 PDF 文件并上传到第 1 单元作业答案提交页面的第 7 题。请勿发送或上传在线文档链接。您必须将 PDF 文件上传到此答案提交页面。