TBR BIO Section 1 Passage 3

[Perseverance7779311]

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Hey guys, in TBR BIO section 1 Passage 3, question 17 states, Which of the following voltage gated positions best represent the repolarization phase. Unfortunately, Im unable to post the pic....but if someone has the book and could tell me how to do that problem, id really appreciate it!!

 

[JMMTB]

When a nerve membrane depolarizes past threshold the sodium channels open up allowing Na to flow in. This depolarizes the membrane further (as seen in the graph). But to prevent the action potential from traveling the opposite direction the sodium channels have an inactive state where they are "open" but no ions can pass through (blocked). Around this same time the Potassium channels open up (they have a slower response than Sodium) and K floods out of the cell. Eventually the sodium channels close "officially" as well as the potassium channels. Na/K pump then restores the membrane potential (some dispute on that).

So the Sodium channel pictured in the text has 2 gates "m" which opens quickly, and "h" which closes slowly.

If m and h are open then the Sodium channel is open. If m is open and h closed then it is in the inactive state. If m is closed and h open then it is in the closed state.

The potassium channel is open or closed (no inactive state) by gate n.

So if we have a repolarization (falling phase) Sodium is inactive and Potassium closed.

gate m=open, h=closed, n=open.

Hope that helps.

 

[Perseverance7779311]

@JMMTB, yes it def helps....thank you very much!! 🙂