Week 3 MPW Lecture 6 Flashcards
What is patch clamping?
A method that is used to measure the current across the membrane
a) Attach a very sensitive electrode to a patch membrane, then we measure while keeping the voltage clamped through the gigaohm seal.
What are the different variations of patch clamping?
Types:
a) Outisde in
b) Inside out patch
c) On cell
d) Whole cell
How is the patch clamp results read?
A graph with many layers;
a) The first layer means no channels open
b) Second layer means 1 channel open etc.
i) Opening and closing is random, the average of opening and closing of channels
What are the types of ion channels present in axons?
2:
a) Voltage gated Na+ channel
b) Voltage gated K+ channel
What does voltage gated mean?
The opening of the channels is determined by the voltage across the membrane
How does the Na+ work?
Steps
a) Closed Na+ channel:
i) The inside of the cell is negative and the voltage sensing alpha helix (is positive) is attracted to the negative inner cell so the channel is closed.
b) Open channel:
i) Voltage sensing helix returns to its place so then Na+ moves inside the cell until the inner cell becomes positive
c) Inactive Na+ channel (refractory period)
i) The plug plugs the channel and when the cell become negative again the helix closes and the process repeats.
How does the K+ work?
Steps
a) Closed K+ channel:
i) The inside of the cell is negative and the voltage sensing alpha helix (is positive) is attracted to the negative inner cell so the channel is closed.
b) Open channel:
i) Voltage sensing helix returns to its place so then K+ moves inside the cell until the inner cell becomes positive
c) Inactive K+ channel (refractory period)
i) The plug plugs the channel and when the cell become negative again the helix closes and the process repeats.
Difference between K+ and Na+ channels?
K+ is slower
2 more common channels that can be seen in any cell?
Na+/K+ pump and Resting K+ channels
What is the Na+/K+ pump?
A pump that maintains the Na+/K+ concentrations in the cell. 3 Na+ out of the cell for 2 K+ coming in.
What is the K+ leak channels?
called resting because they are open even when the cell is at rest. K+ is being leaked out, keeps the cell membrane negative
How do you define a “negative” membrane potential?
When the nearby area of the membrane is negative
How do the Na/K pump and K+ resting channel work together to maintain a negative membrane potential?
Since there is more K+ inside the cell than outside, we remove the K+ to get in Na+ to get the cell more positive again.
