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NSCI 200 Lecture 5 Questions by LAM
1. Glutamate receptors pass both K and Na upon binding glu. Why does this cause
depolarization?
 brings the membrane potential to around 0mV (average equilibrium potential)
2. Describe shunting inhibition
 cl channels are open, EPSP tries to depolarize membrane, but since Vm = Ecl, nothing
happens
3. Describe the early experiments to show that there was some kind of electrical signaling
going on.
 Galvani: vital energy, Volta: electricity sensed from the surroundings, Matteucci: both were
right
4. Which of the following statements was not part of Bernstein’s hypothesis or predictions?
a. Resting membrane is more permeable to K+ ions.
b. Action potential due to transient increase in permeability to all ions
c. Asymetric gradient of ions inside and outside cells
d. Voltage should approach +40 mV at the peak of an action potential
e. None of the above
 d. he assumed that the peak would be 0 mV
5. When Hodgkin and Huxley measured the action potential in a squid axon, they found that
peak topped off at around -40 mV. What does this result suggest via the hypotheses of
Bernstein?
 that an action potential is not due to the transient increase of permeability to ALL ions
6. Understand how the voltage clamp technique works.
 **
7. How come the current of the early component of the action potential reverses as you
increase the membrane potential past +60mV?

8. ____ Seletively blocks voltage sensitive K+ ions. _____ selectively blocks Na channels.
 TEA, TTX
9. You are conducting an voltage clamp experiment with a cell whose membrane is
permeable to Na+. The ENa+ is +58mV. You bring the membrane potential to 0 mV and
measure 5 mA of current. What is the conductance of Na+ channels in this membrane?
 **
10. Which of the following statements is NOT true?
a. During the action potential, Na conductance is early and transient.  true
b. The ionic conductance of K is greatest at negative potentials
c. An action potential can be initiated in the relative refractory period, but its peak
will have a lower amplitude.  true
d. The Na channel has three conformation states while the K channel has two.true
e. Two of the above
f. None of the above
 **
NSCI 200 Lecture 5 Questions by LAM
11. What is the use of channel inactivation?
 unidirectional flow of information
1. Because the average equilibrium potential of Na and K is around 0, which is more
positive than the resting membrane potential.
2. If an EPSP comes in to activate the cell, the depolarization will be countereacted
(shunted) by the flow of Cl into the cell.
3. Luigi Galvani believed that the muscles generated electricity by using “vital energy”.
Alessandro Volta believed that the muscle was simply responding to an electric current.
Matteucci demonstrated that both of the above researchers were right.
4. d. He assumed that the peak would be at 0 mV
5. That the permeability in the membrane during an AP is not equal for all ions.
6. Too lazy to explain. Feedback circuit, measure current fed back into cell.
7. The early component represents Na+ permeability. Since the ENa is around +60 mV, as
you go from below this value to above this value, the current of Na ions will reverse
according to its electrochemical gradient.
8. Tetraethyl-ammonium (TEA); tetrodotoxin (TTX
9. g = I/(V-E) = 5 mA/(0mV -58 mV) = 0.086 S = 8.6 mS
10. b (conductance for Na and K both plateau at positive membrane potentials)
11. To allow a single direction of action potential propagation.