AnS 214 SI Session 7
Monday, 9/21, 7pm
A. Resting membrane potential.
1) What is the name of the structure responsible for upkeep of resting membrane potential in the cell?
2) At what rate are ions exchanged across this structure?
3) This exchange results in what net movement of charge and how does this relate to resting membrane potential?
4) This process requires the supply of what molecule to keep the pump functional?
B. Action potential.
Fill in the blanks of the diagram. Then, complete the sentences describing each numbered step of the diagram.
1) The arrival of ______ions at the ______causes ______
______
______.
2) The arrival of positive charge may raise the membrane potential to a critical value called
______, which triggers the cell to ______
______
______.
3) The massive ______of ______ions causes even more ______channels to open. The result is ______
______
______.
4) At the point where membrane potential reaches 0mv, ______channels begin to close, while ______channels start to open. This results in ______
______,
changing the direction of positive charge flow. This manifests as a ______on the diagram.
5)Because of the now open ______channels, positive charge is now ______the cell, which causes the membrane potential to ______
______.
6) Because K+ channels don't close fast enough ______
______, and the axon's membrane potential is referred to as ______.
7) The action of ______returns membrane potential back to a resting value of ______.
C. Refractory Period.
Fill in the blanks on the diagram.
1) Why can there be no action potential in the part of the diagram exhibiting the peak in membrane potential?
2) Why is there a decreased chance of action potential during depolarization.
3) Draw two additional lines on the diagram representing the changes in membrane permeability to Na+ and K+. How does this correspond to changes in membrane potential?
D. Signal conduction along myelinated fibers.
1) In the above diagram, what cell type is labeled as '2'?
2) If this axon was located in the brain, what cell type would '2' refer to?
3) When sodium channels open on the axon labeled '1', where do incoming ions travel? (draw arrows)
4) What effect does the Schwann cell have on the travel of Na+ ions as they travel under '2'?
5) What happens as the ions reach the axon piece labeled '3'? What is this type of signal propagation called?
6) Do any ions reach the point labeled '0'? If so, why do they not stimulate an action potential?
7) Label pieces 0,1,3 as action potential, relative refractory period and absolute refractory period, relative to what is happening at that axon piece.