1-Membrane Potential

Question 1

membrane potential

definition

Answer 1

difference in electric potential b/t interior and exterior of cell
must have uneven distribution of electrolytes + active transporters or ion channels

resting membrane potential when cell at rest

Question 2

Na+

intra or extracellular?

Answer 2

EXTRACELLULAR
142 mEq/L out
10 mEq/L in

Question 3

K+

intra or extracellular?

Answer 3

INTRACELLULAR
140 mEq/L in
4 mEq/L out

Question 4

Cl-

intra or extracellular?

Answer 4

EXTRACELLULAR
103 mEq/L out
4 mEq/L in

Question 5

electrochemical equilibrium potential steps

Answer 5

1. initial ion movement driven by chemical gradient/concentration aka high to low
2. voltage created bc of charge difference
3. ions of same charge repelled back (electric driving force)
4. equilibrium when electric and chemical flux balanced

Question 6

equilibrium potential

Answer 6

indicates strength of chemical driving force/concentration gradient

calculate by E = 61.5 x log [ion outside]/[ion inside]

61.5 is for constant

Question 7

net charge neutrality

Answer 7

extremely small changes/imbalance = big potential change

so both sides remain net charge neutrality

Question 8

membrane potential in vivo

Answer 8

1. lipid/protein membrane separates intra/extracellular fluids
2. uneven distribution of K, Na, Cl
3. ion channels selectively pass ions

Question 9

Vrest

Answer 9

resting membrane potential determined by which ion is more permeable (channels and concentration)

ex: Ek = -95 and ENa = +70 so Vrest primarily determined by K and closer to Ek value at rest

Question 10

ionic gradients

at rest, K/Na

Answer 10

constant K efflux (out) + constant Na influx

Na/K pumps restore concentration gradients so K higher and Na lower inside cell

Question 11

Na/K Pump

Answer 11

3 Na/2 K

uses ATPase so can be inhibited by ouabain but won’t lose resting potential immediately

Question 12

calcium ions

Answer 12

concentration low in cytoplaasm, mostly in SER

at rest membrane usually impermeable to Ca so do not contribute to rest membrane potential

Question 13

polarization

Answer 13

hyperpolarization = potential becomes more negative
depolarizatio = potential becomes less negative

Question 14

hyperkalemia

Answer 14

abnormally high blood potassium = abnormal function muscle, heart, nerves, depolarize

normal = 3.5-5.0 mM
mild= 5.1-6.0
moderate= 6.1-7.0
severe = 7.0 +

hypokalemia will hyperpolzarize

Question 15

change external [K]

what happens?

Answer 15

if increase= Ek becomes less negative
membrane potential Vm becomes less neg

if decrease= Ek more negative
Vm more negative

arrows/values shift in same direction

Question 16

change extracellular [Na]

what happens?

Answer 16

if decrease= ENa dec + membrane slightly more negative, Na graph goes down but only small change for Vm bc Na less contribution

if increase= ENa more positive + membrane slightly less negative