RMP

Question 1

equilibrium potential

Answer 1

the diffusion potential that exactly balances or opposes the tendency for diffusion down the concentration gradient

Question 2

nernst equation

Answer 2

electrical force required to just balance a given concentration gradient force

• Eion = (60/z)(log [ion] out/ [ion] in

Question 3

the sodium potassium pump contributes what mV to RMP

Answer 3

5-20 mV 3 Na+ out; 2 K+ in maintains large chemical gradient for Na+ and K+ that sustains RMP

Question 4

what is the mV of the ECF at RMP

Answer 4

0 mV

Question 5

all cells have some RMP; is the ICF + or -? What determines the RMP of a cell?

Answer 5

cytoplasm is negative (-20 to -110) depends on ions present; permeability of each ion; electrochemical gradient of each ion

Question 6

how are permeability and conductance related

Answer 6

proportionally

Question 7

what is the equation to find the relationship between conductance (g) and resistance (R)?

Answer 7

g = 1/R

Question 8

which is bigger conductance of K+ or Na+?Why

Answer 8

gK+ >>gNa+ There are many more continuously open channels for K+ at “rest”

Question 9

how is conductivity of an ion (g(ion)) increased?

Answer 9

open previously closed ion channels or synthesize, then insert additional open ion channels

Question 10

what is the ionic Ohms law used to find

Answer 10

estimates membrane potential knowing equilibrium potentials and conductances for each ion in question

Question 11

what is the equation for ionic Ohms law

Answer 11

E membrane = (g_KE_K + g_NaE_Na + g_ClE_Cl) / (g_K + g_Na + g_Cl)

• Eion: Ek = -92; ENa = + 59; ECl= -83

Question 12

if E membrane becomes more neagtive, the cell is said to be what?

Answer 12

hyperpolarized

Question 13

what happens when a cell becomes excited

Answer 13

ability of a membrane to transiently change its permeability (i.e. conductance) to certain ions rapidly upon stimulation

Question 14

What happens to the RMP of a cell in a patient who is severly hypokalemic?

Answer 14

• gradient for K+ increases causing E_k to become more negative which causes RMP to become more neagtive
• a more negative RMP is also termed hyperpolarized

Question 15

Hypokalemia leads to a hyperpolarized RMP. What does this mean for muscle cells

Answer 15

If muscle cells have a hyperpolarized RMP, they do not contract very readily

• this could lead to muscular paralysis; suffociation (diaphragm); and asystole

Question 16

what happens to the RMP of a cell in a patient who is hyponatremic?

Answer 16

it does not change appreciably because the conductivity of Na+ is very low