{[ promptMessage ]}

Bookmark it

{[ promptMessage ]}

03 Quiz info

# 03 Quiz info - LESSON 3 QUIZ INFORMATION AND EXPLANATIONS...

This preview shows pages 1–4. Sign up to view the full content.

LESSON 3 QUIZ INFORMATION AND EXPLANATIONS FOR SELECTED QUESTIONS The average for Lesson 3 Quiz was 84.5% and the distribution of scores is illustrated in the histogram below Six students scored 90% or above!!! Below are some explanations to the more difficult questions. If you have further questions about these or others, please post them in the Lesson 3 Discussion Forum or email me. If you missed any of the questions on this quiz, you may benefit from reading these explanations . Many of the questions in this quiz can be answered by using the Very Important Principles found in Part 6 of Lesson 3 Outline. If you understand these principles and can apply them, most of the difficult parts of membrane electrophysiology will become easy!! These Very Important Principles (VIPs) are summarized below. If you are considering the effects of changes in the chemical gradients, use the following principles. Very Important Principle #1: Changes in the chemical gradient of a given ion will change the equilibrium potential (E ion ) for that ion. Very Important Principle #2: The membrane potential (E m ) is highly sensitive to changes in the chemical gradient, and therefore the equilibrium potential, of the most permeable ion. The Goldman equation takes into account the relative permeabilities. If you are considering the effects of changes in permeability (opening and closing of ion channels), use the following principles. 1

This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document
Very Important Principle #3: If the permeability of the membrane to a given ion increases, the membrane potential will move closer to that ion’s equilibrium potential. Very Important Principle #4 : If the permeability of the membrane to a given ion decreases, the membrane potential will move away from that ion’s equilibrium potential. A corollary to Very Important Principles #3 and #4 : If E m is equal to an ion’s equilibrium potential, there will be NO net diffusion of that ion and no change in E m , no matter how permeable the membrane becomes to that ion. Questions 1 - 8 For questions 1 through 8, use the following hypothetical situation. Assume that the cells in the questions have these concentration gradients for the ions. Extracellular mM Intracellular mM Eion A + 2 200 -123 B + 300 30 61.5 C ++ 30 1 45.4 D - 300 30 -61.5 Now, before you even start looking at the questions, I strongly suggest that you ALWAYS draw the information provided on a voltage as a function of time graph (below). I’ve put the information provided in the following graph. Note the actual membrane potential, the voltage (E m ) across the membrane, is not provided. Only the equilibrium potentials for various ions were given. 2
So, with the situation illustrated, let’s look at a few of the questions. #3. If the cells were impermeable to all ions, and the extracellular [A + ] increased to 20 mM, E m will become more positive.

This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document
This is the end of the preview. Sign up to access the rest of the document.

{[ snackBarMessage ]}

### Page1 / 15

03 Quiz info - LESSON 3 QUIZ INFORMATION AND EXPLANATIONS...

This preview shows document pages 1 - 4. Sign up to view the full document.

View Full Document
Ask a homework question - tutors are online