Trans - Neuronal Excitability I

Question 1

cytoskeletal fast transport uses

Answer 1

kinesin

Question 2

cytoskeletal fast retrograde transport uses

Answer 2

dynein

Question 3

special feature of axon hillock

Answer 3

large number of Na gates for start of impulse propagation

Question 4

end of axon

Answer 4

terminal bouton

Question 5

normal resting membrane potential

Answer 5

-70 mv at rest

Question 6

resting membrane potential is mainly influenced by

Answer 6

1. permeability of the membrane for each diffusible ion species
2. cncentration of ions inside and outside the cell

Question 7

3 mechanisms to generate RMP

Answer 7

1. transmembrane K gradient through nongated leak channels
2. Donnan effect.
3. Na-K pump

Question 8

main mechanism to generate RMP

Answer 8

transmembrane K gradient through nongated leak channels

Question 9

Na-K pump contributes how much to RMP

Answer 9

20%

Question 10

concentration gradient of K

Answer 10

high inside the cell - tends to move out

Question 11

concentration gradient of Na

Answer 11

high outside the cell - tends to move in

Question 12

concentration gradient of Cl

Answer 12

high outside the cell - tends to move in

Question 13

Gibbs-Donnan equilibirum

Answer 13

in the presence of a nondiffusible ion, diffusible ions distribute themselves so that at equilibrium, their concentrations are equal

Question 14

consequence of Gibbs-Donnan equilibrium

Answer 14

differential distribution of diffusible ions when a nondiffusible ion is present

Question 15

Donnan effect

Answer 15

asymmetric distribution of permeant ions at equilibrium resulting in an electrical difference across the cell membrane

Question 16

Donnan effect - to maintain electrical neutrality, there will always be a (1)______ K concentration inside the cell and a (2)_____Cl concentration outside

Answer 16

1. greater

2. greater

Question 17

side effect of donnan effect

Answer 17

accumulation of osmolytes in ICF - corrected by Na-K pump

Question 18

Donnan effect - proteins within the cell limit diffusion of what ion down its concentration gradient

Answer 18

Cl

Question 19

Donnan effect - what two forces are created in relation to movement of K

Answer 19

1. force pulling K in –> due to electrical gradient

2. force pulling K out –> due to chemical gradient

Question 20

force that moves solutes

Answer 20

diffusion pressure

Question 21

Nernst equation - requirements

Answer 21

semipermeable membrane, diffusible species present, electrical and chemical gradient present

Question 22

relationship of diffusion pressure and electrical pressure in equilibrium

Answer 22

equal

Question 23

equilibrium potential of K

Answer 23

-90mv - tends to go out

Question 24

equilibrium potential of Na

Answer 24

60mv - tends to move in

Question 25

equilibrium potential of Cl

Answer 25

-70mv - does not move (diffusion pressure = electrical pressure)

Question 26

what ion is really responsible for resting membrane potentials? why?

Answer 26

K, because it is freely diffusible at rest (K leak channels)

Question 27

why is the equilibrium potential of K different from the RMP?

Answer 27

Na channels are not completely closed –> small influx of positive ions, bringing the potential up from -90 to -70

Question 28

Goldman Constant Field Equation

Answer 28

takes into consideration all ions involved, used to calculate the true value of RMP

Question 29

why can’t the Nernst equation be used to find the value of RMP

Answer 29

Nernst takes into account only one ion; there are many in this system

Question 30

most flux of the 3 major ions

Answer 30

K (high permeability)

Question 31

least flux of the 3 major ions

Answer 31

Cl (does not move)

Question 32

[T/F] resting membrane potential is in absolute equilibrium

Answer 32

F

Question 33

[T/F] resting membrane potential is constant

Answer 33

T

Question 34

with lack of energy from ATP, what will happen to RMP? why?

Answer 34

it will dissipate because the ions are not in absolute equilibrium

Question 35

which ions have almost no contribution to RMP according to the Goldman Equation

Answer 35

Na, Cl

Question 36

action of Na-K pump

Answer 36

3 sodium out, 2 potassium in

Question 37

function of Na-K pump

Answer 37

1. prevent cell swelling

2. maintain RMP at -70mV

Question 38

[T/F] energy is required to maintain the steady state equilibrium of RMP

Answer 38

T