Download Bio 3411 Problem Set 9 Name: (Due Monday, November 28th 2011

Bio 3411 Problem Set 9
(Due Monday, November 28th 2011)
Name:
Golden Rule: Two Sentences or Less for each question.
1. a. What is the difference between reversal and equilibrium potentials? (.5)
b. What is the net current at the reversal potential of a channel? (.5)
c. If Na+ and K+ currents exist at the reversal potential for a channel, which direction do
they move? (.5)
2. a. You are a goddess of molecular evolution. You want to make two new leak channels;
one selective for Cl- and one selective for Ca++. Name two properties for each channel
that would help it be selective. (1)
b. You are a tempestuous goddess. Leak channels are no longer good enough. You now
desire a voltage gated channel. As you build this new channel what protein domain could you
include that would confer voltage sensitivity? How would this domain regulate ion flow? (1)
3. a. The reversal potential for an acetylcholine-gated channel is +20mV. Assume that it is
only permeable to Na+ and K+. Given that EK is -100mV and ENa is +100mV, which ion
does the channel have a greater conductance for? (.5)
b. Using the GHK equation altered to calculate relative conductances (as given in class) ,
calculated the relative conductances between Na+ and K+. Show your work. (1)
4. What are the differences between synaptic transmission at the Neuromuscular Junction and
synaptic transmission in the CNS? (1)
Bio 3411 Problem Set 9
(Due Monday, November 28th 2011)
Name:
5. You are studying the neuromuscular junction (NMJ) and make the follow recordings of
action potentials in the presynaptic and postsynaptic terminals in response to electrical
stimulation of the motor neuron under control conditions. Sketch what you predict your
recordings will look like under the conditions listed below (2.5 points total, 0.25 points each)
Presynaptic
Postsynaptic
Control:
0.25 mM [Ca]external
Sodium channel blocker
Calcium buffer inside
post synaptic
terminal
Calcium buffer inside
presynaptic terminal
Calcium channel blocker
Bio 3411 Problem Set 9
(Due Monday, November 28th 2011)
Name:
6. The figure below shows whole cell recordings of current vs. time in a voltage clamp
experiment. A and C are controls before the addition of a drug or toxin; B and D are
currents after the addition of the indicated agents.
a. What ions are responsible for the recordings in B? In D? (1)
b. Why do the recordings in D flatline across all voltages? (.5)