I am a little confused about the action potential concept (see nervous system)
I have 3 multiple-choice questions that I need help with:
Which is the correct sequence of events that follows a threshold potential:
1.the membrane becomes depolarized
2.sodium channels open and sodium ions diffuse inward
3.the membrane becomes repolarized
4.potassium channels open and potassium ions diffuse outward while sodium is actively transported out of the cell
A)3,2,4,1
B)2,1,4,3
C)2,1,3,4
D)1,2,4,3
E)4,1,3,2
My answer is C, but not sure because the questions refers to the sequence of events THAT FOLLOWS A THRESHOLD POTENTIAL. The correct answer could be D?
Second questions is:
An action potential:
A)is essential for impulse propagation
B)involves the influx of negative ions to depolarize the membrane
C)involves the outflux of negative ions to depolarize the membrane
D)involves the outflux of positive
ions to depolarize the membrane
E)is initiated by potassium ion movements
My answer is A
Match the following:
1.Period when the interior of the cell becomes less negative due to an influx of sodium ions
2.Term a nerve impulse when transmitted
A)action potential
B)saltatory conduction
C)repolarization
D)depolarizarion
My answer is 1.D and 2.A
Thank you for your help.
I think if you read the following 2 sites it will help you a lot.
http://faculty.washington.edu/chudler/ap.html
http://en.wikipedia.org/wiki/Action_potential
Yes, after you read the site mentioned by Lance, you should understand that your answer to the first question is not correct. If you are still unsure why, please repost!
Thank you Dan.
After visiting the first website, I am changing the answer to D. So, the explanation is that the cell membrane becomes depolarized first and then Na channels opens for the positive ions to difusse inside?
Please let me know if my understanding is correct.
The sodium channels open, and sodium goes in. This causes DEPOLARIZATION. Then, the potassium channels open, and potassium comes out. This causes REPOLARIZATION (cell goes back to its resting state).
So, the actual order is....2, 1, 4, 3.
Do you see that?
Yes, you have understood it correctly. The correct sequence of events that follows a threshold potential is:
1. The membrane becomes depolarized
2. Sodium channels open and sodium ions diffuse inward
3. The membrane becomes repolarized
4. Potassium channels open and potassium ions diffuse outward while sodium is actively transported out of the cell
So the correct answer is option C) 2, 1, 3, 4.
For the second question, you are correct. An action potential is essential for impulse propagation. It is the electrical signal that travels along the nerve cell, allowing communication between different parts of the nervous system. So the answer is option A) is essential for impulse propagation.
For the matching question, you have also identified the correct matches. The period when the interior of the cell becomes less negative due to an influx of sodium ions is called depolarization, which matches with option 1) D. And the term for a nerve impulse when transmitted is called action potential, which matches with option 2) A.
Overall, your understanding is correct. Keep up the good work!