Membrane Potential

Question 1

Is extracellular or intracellular [Na+] higher?

Answer 1

Extracellular

Question 2

Is extracellular or intracellular [K+] higher?

Answer 2

Intracellular

Question 3

Is extracellular or intracellular [Ca+] higher?

Answer 3

Extracellular

Question 4

Is extracellular or intracellular [Mg2+] higher?

Answer 4

Extracellular

Question 5

Is extracellular or intracellular [Cl-] higher?

Answer 5

Extracellular

Question 6

Concentration (mM) x valence = ?

Answer 6

mEQ

Question 7

Why can’t a a cell with only a lipid membrane have a membrane potential?

Answer 7

Bulk electroneutrality and ions cannot cross the membrane

Question 8

What is being balanced when K+ leak channels reach an equilibrium state?

Answer 8

Concentration gradient of the higher intracellular potassium and the electric resistance to flow (inside becomes more negative)

Question 9

Abbreviated Nernst Equation

Answer 9

Ek=(61)(mV)log(Ko/Ki)

Question 10

Equation describing the resting equilibrium state of a membrane with more than one permeable ion

Answer 10

Goldman Equation (G-H-K equation)

Question 11

The external membrane surface typically has a negative or positive charge?

Answer 11

negative (despite the extracellular fluid itself being relatively positive)

Question 12

Do monovalent or divalent cations bind to the negative charges on the extracellular membrane leaflet?

Answer 12

Divalent. Monovalent “not charged enough” to bind.

Question 13

Decreases in extracellular Ca2+ and Mg2+ are called what, respectively?

Answer 13

Hypocalcemia and hypomagnesemia

Question 14

“unscreened” negative charges on the cell membrane outer surface have what affect on the charge difference across the membrane?

Answer 14

Reduce the total charge difference. Resting potential less negative

Question 15

Ease of movement of a substance through the cell membrane

Answer 15

Membrane Permeability (Pm)

Question 16

Determined by the number of open ion channels in the membrane

Answer 16

Ion membrane permeability

Question 17

Ease of movement of electric charge through the cell membrane.

Answer 17

Membrane conductance

Question 18

Unit for membrane conductance

Answer 18

Siemens (S)

Question 19

Relationship between membrane conductance and resistance

Answer 19

Resistance is the inverse of conductance

Question 20

Rate of charge flow across the cell membrane

Answer 20

Membrane current (measured in Amperes - A)

Question 21

Total net difference in electrical charge distribution across the cell membrane

Answer 21

Membrane potential (measures in Volts - V)

Question 22

How is the driving force for an ion determined?

Answer 22

Difference between membrane potential and an ion’s equilibrium potential

ΔVion = (Vm - Eion)

Question 23

(Driving Force) x (Conductance) = ?

Answer 23

current

Question 24

Outward current. Makes the cell interior more negative or positive?

Answer 24

More negative (efflux of cations or influx of anions)

Question 25

Inward current. Makes the cell interior more negative or positive?

Answer 25

More positive (influx of cations or efflux of anions)

Question 26

Positive current is outward or inward?

Answer 26

Outward

Question 27

Negative current is outward of inward?

Answer 27

Inward

Question 28

Capability (of the membrane) to store electrical charge

Answer 28

Membrane Capacitance (measured in Farads - F)

Question 29

Describes the lag between current flow and change in membrane potential. Determined by total membrane resistance (Rm) and total membrane capacitance (Cm)

Answer 29

Membrane Time Constant

Question 30

Why does membrane potential change slower than membrane current?

Answer 30

Membrane current changes instantaneously if there's a change in driving force or conductance but it takes time to rearrange the the charges stored on the cell membrane.

Question 31

Two determinants of membrane capacity to store charge

Answer 31

Surface area (pos relationship) and thickness (neg relationship)

Question 32

Membrane Time Constant = ?

Answer 32

(resistance) x (capacitance)

Question 33

total membrane conductance is the product of... (2)

Answer 33

(number of open channels) x (individual channel conductance)

Question 34

Increasing Rm will have what effect on the time constant

Answer 34

increases the time constant

Question 35

Increasing Cm will have what effect on the time constant

Answer 35

increases the time constant

Question 36

Describes the decay in effect over distance along a cylindrical membrane area. Higher value means more current flow.

Answer 36

Length Constant (λ)

Question 37

Determinants of the length constant (2)

Answer 37

membrane resistance (Rm) and axial resistance (Ra)

Question 38

Resistance to current flow along cylindrical area of membrane

Answer 38

axial resistance

Question 39

Does higher axial resistance increase or decrease the length constant

Answer 39

decrease

Question 40

Large diameter axons have a larger or smaller axial resistance?

Answer 40

Small Ra

Question 41

Small diameter axons have a larger or smaller axial resistance?

Answer 41

Large Ra