A rather tame ltxnsp wasrecently found on Easter Island by a retired neurophysio
ID: 3220 • Letter: A
Question
A rather tame ltxnsp wasrecently found on Easter Island by a retired neurophysiologist. Hereported the following measurements of ECF and ICF concentrations(in millimoles):
ICF
ECF
Pr+
0
150
Na+
?
?
K+
10
100
Cl-
109
250
HCO3-
1
10
He lacked the proper instrumentsfor determining Na+concentrations, butwas rather certain that no other major ions were present in the ECFand ICF. Can you calculate either concentration for him? (Show allcalculations)
He measuredEm(membrane potential) as -58 mvat 20°C (K = 58 mv at 20°C). What ions should be in a passive equilibrium across themembrane? Why?
He determined that the risingphase of the action potential in ltxnsp neurons was due to a suddenincrease in PK. What should be the sign andapproximate amplitude of the voltage change of these actionpotentials? Why?
Which ions are activelytransported? Why?
Suppose that in other ltxnspcells the HCO3-in the ICF = 10mM,1mM in the ECF, and is passively distributed across the membrane.What should be the sign and magnitude of their membrane potential(Em)?
ICF
ECF
Pr+
0
150
Na+
?
?
K+
10
100
Cl-
109
250
HCO3-
1
10
Explanation / Answer
I have been assigned the same problem did you figure out how to do it? I m not sure if Im doing it right.
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