Deck 17: Origin of the Membrane Potential

Question 1

Increasing gNa with ou t af fe ctin g a ny o f th e o the r c on du cta nc es , sh ou ld

A) Bring Em closer to ENa
B) Depolarize ENa on ly
C) Hyperpolarize ENa
D) Depolarize Em because of changes in ENa
E) Increase IK

Answer 1

A

Question 2

The eq uilib riu m po ten tial

A) Is the potential at which total current of all ions across the m em brane is zero
B) Depends on the permeability of the ion
C) Is the potential at which the electrical force for tra ns po rt o f th e io n a cr os s th e m em br an e is zero
D) Occurs when the concentration of ions on both sides of the mem brane is the same
E) Oc curs w hen the cu rrent ca rried by the ion is zero

Answer 2

E

Question 3

At the resting membrane potential

A) Po tas siu m is a t its e qu ilibriu m po ten tial
B) The tota l curren t acro ss th e m em bran e is zero
C) Sodium is at its equilibrium potential
D) The re is an inward flow of K+ ions
E) Both A and C are correct

Answer 3

B

Question 4

The Na,K-ATPase

A) Makes the resting membrane potential a little more negative
B) Makes no contribution to the resting membrane potential
C) Is electroneutral
D) Is in hib ited by te tro do tox in
E) Both A and C are correct

Question 5

The slope conductance for the ion x is defined as

A) gx = Ix / Em
B) gx = dIx /dEm
C) gx = Px d [X]/dx
D) gx = Ix / (Em - Ex)
E) None of the above

Question 6

The equilibrium potential for an ion across a mem brane is the

A) Potential at which the total current across a m em brane is zero
B) Electrochemical potential difference for the ion
C) Potential that stops diffusion of the ion across the membrane
D) Potential that opposes osmotic flow
E) Resting mem brane potential

Question 7

The chord conductance for the ion x is defined as

A) gx = Ix / Em
B) gx = dIx /dEm
C) gx = Px d [X]/dx
D) gx = Ix / (Em - Ex)
E) None of the above

Question 8

The EK for a cell is -90 mV and E Na is +55 mV. At a resting membrane potential o f -70 mV and assuming conductances ONLY to Na+ and K+,

A) There is an outward K+ current
B) There is a net inward current
C) There is an net outward current
D) gNa > gK
E) None of the above

Question 9

The resting mem brane potential

A) Is set by the Na,K -ATPase
B) Depends on the permeabilities and equilibrium potentials of all ions
C) Is closest to the equilibrium potential for Ca₂+
D) Is th e s am e fo r all c ells
E) Is the potential at which all ions are in equilibrium

Question 10

The Goldm an-Ho dgkin-Katz current equ ation predicts the current for the ion is zero

A) W hen Em = the resting mem brane potential
B) W hen [X]o = [X]i
C) W hen Em = 0
D) When E m = Ex , the equlibrium potential for the ion
E) The current is never zero

Question 11

Incre asin g the extra cellular [K+] by itself should

A) Increase EK (m ake it less negative)
B) H ype rp ola rize the ce ll
C) D ep ola rize the ce ll
D) Have no effect on EK because gK would not change
E) Both A and C are correct

Question 12

The EK for a cell is -90 mV an d E NA is + 55 m V. At a resting membrane potential of -70 mV and assuming conductances ONLY to Na+ and K+,

A) There is an inward K+ curr ent
B) There is an outward Na+ current
C) gNa > gK
D) The Na,K-ATPase pumps Na+ into and K+ ou t of the ce ll
E) The tota l curren t acro ss th e m em bran e is zero

Question 13

Which o f th e fo llow ing is N O T tru e o f th e e qu libriu m po ten tial?

A) It is the potential at which the flux of an ion is zero
B) It is the potential at which diffusive force balances electrical force
C) It is the potential for which 6µ for an ion is zero
D) It is the p oten tial at w hich the co nd ucta nce for an ion is z ero
E) It is the potential at which the Nernst equation gives the mem brane potential

Question 14

The ch or d c on du cta nc e e qu atio n fo r th e m em br an e p ote ntia l is va lid

A) All th e tim e
B) On ly whe n dV /dt =0
C) Only at the resting membrane potential
D) Only at the equilibrium potential
E) Only at the peak of the action potential

Question 15

The eq uilib riu m po ten tial f or an ion is

A) Given by the chord conductance equation
B) The po tential at w hich the n et pa ssive flux of th e ion is zero
C) Always negative inside
D) W hen the conductance balances the pump
E) W hen 6 G ATP-ADP + Pi = 0

Question 16

If EK = -85 mV and E m = -70 mV , the potassium current is

A) Positive, m eaning that IK is outward and K
B) Po sitive, m ean ing tha t IK is inward and K flow is inward
+
C) Ne gative , m ean ing tha t IK is outward and K +
Flow is outward
D) Ne gative , m ean ing tha t IK is inward and K
E) Cannot tell without knowing gK flow is inward

Question 17

The equilibrium potential of an ion is the potential at which

A) There is the same concentration of the ion on both sides of the mem brane
B) The electrical force on the ion is zero
C) 6µ for pa ssive ion tran spo rt acros s the me m bran e is zero
D) The conduc tance for an ion is zero
E) 6µ for ion transport is exactly matched by the 6µ for AT P h ydr olys is