Lecture 2: Permeability and ions in solution

Question 1

define driving force

Answer 1

E of amount of force behind every ion

difference between Electrical potential of the membrane and that of the ion
V = E = Driving force = (Em - Eion)

Question 2

Equilibrium Potential

Answer 2

= electrical potential ONLY @ equilibrium
point

Question 3

E Ion

Answer 3

where the net movement or flux of an ion is 0, depends on the ion and the amount added to the system
can be determined using the Nernst equation
@ this point the ion is at equilibrium
when all the ions are at their respective equilibrium there is no net flux

Question 4

Na+ physiological concentrations

Answer 4

tiny inside, MASSIVE outside
5,15 : 145 mM

Question 5

K+ physiological concentrations

Answer 5

MASSIVE inside, tiny outside
140 : 5mM

Question 6

Ca+ physiological concentrations

Answer 6

negligible inside, tiny outside
- because of this it’s the best ion to be chosen for excitability, tiniest change will be important
10^-4 : 1-2 mM
small concentrations but many many fold difference

Question 7

Cl- physiological conditions

Answer 7

small inside, MASSIVE outside
5-15: 110 mM

Question 8

Nernst equation

Answer 8

E ion = 58mV log ([ion]o/[ion]i)
for - ratio is flipped

Question 9

Ohms Law (conductance and DF version)

Answer 9

I ion = ion (Em-Eion)

Question 10

The Goldman Hodgkin Katz equation

Answer 10

sum of Nernst equations for multiple ions, and has permeabilities included as weighing factors, negative charged ion ratio is flipped inside out

Question 11

Hyper-polarization

Answer 11

potential in the negative direction very little happens current wise

Question 12

depolarization

Answer 12

potentiated in the positive direction –> squares up
induces activity, current movement
fast inward current of Na+ followed by the slow outward current of K+

Question 13

Current voltage relationships (I-V relationships )
exp. vs theory

Answer 13

Experimental =/= Theoretical (ohmic relationship)
voltage vs current
x-intercept = equilibrium potential –> Where I is 0
y-intercept = where electric potential is 0 mV
above the x-axis –> outside current
below the x –> inward current
K is always out ward, Na only goes out ward at really high Ems FAR FAR from physiological range
slope is proportional to conductance

Question 14

Theoretical (Ohmic) I-V

Answer 14

linear relationship
regardless of state line if extended will always cross E ion
inactive state –> less steep line
active state steeper line
drastic/vertical line between the 2 states quick change in voltage

Question 15

Experimental I-V

Answer 15

not as steep a change between the 2 states
relationship not perfectly linear
recovery is helped by the outward