Kims objectives

Question 1

how is membrane potential established

Answer 1

Vm
based on charge imbalance
driving for and permeabililty 
basically just ions being uneven
ground is outisde cell

Question 2

Equilibrium potential, Ex

Answer 2

nernst potential so based on concentration and charge
K is like -95
Na is like 35
Cl is near -Vm

Question 3

Driving force

Answer 3

DF=Vm-Ex
VmEx outward (DF>0)
Vm=Ex no net

Question 4

voltage clamp

Answer 4

decide the voltage
record current needed to maintain
squid axon example

Question 5

current clamp

Answer 5

decide the current, measure the voltage

Question 6

action potential generation

Answer 6

EPSP have AMPA receptor that opens to letting Na in to depolarize
IPSP have GABA receptor letting in Cl to hyperpolarize
rising, falling, undershoot

Question 7

voltage gated channels

Answer 7

K has 4 subunits and one gate, slow to activate and deactivat, opens with depolatiation just slowlly
Na has alpha and beta subunits, two gates, one opens opens at threshold and then the other closes after 1ms and stays closed until repolarization

Question 8

currents underlying action potential phases

Answer 8

rising phase is inward current of Na

falling phase and undershoot - K outward current

Question 9

refractroy periods

Answer 9

make it unidirectional because of Na inactivation

Question 10

conductance

Answer 10

flow of ions through channels

Question 11

conductance

Answer 11

flow of ions through channels

g in R=1/g

Question 12

capacitor

Answer 12

stores charge
analogous to neuronal membrane
negative inner, positive outter

Question 13

capacitor

Answer 13

stores charge
analogous to neuronal membrane
negative inner, positive outter

Question 14

What happens when depollarized Vm=-40

Answer 14

Force on Na decreases because it closer
Force on K increases because further
force on Cl increases
outward current inward Cl

Question 15

current

Answer 15

flow of positive charge so direction of Na and opposite of Cl

Question 16

hyperpolarized to -90

Answer 16

Force on Na increases because further
no net force on K because nearer
force on Cl reverses
inward current outward cl

Question 17

Permeabliity

Answer 17

determines resting membrane potetnial
basically if youre more permeable then Vm is closer to Ex
K>Na»Cl so Vm is near K but not K because of Na
so flux of Na and K aer equal and opposite at rest

Question 18

what determines resting potential

Answer 18

GHK

Concentration and permeability of Na and K

Question 19

what factores determin net movement

Answer 19

driving force and permeablity

DF=Vm-Ex

Question 20

what influences driving force

Answer 20

concentration
electrostatic force
membrane potential

Question 21

patch clamps

Answer 21

by either just grabbing or pinching off sections you can measure current from different directions

Question 22

time constatn

Answer 22

Tau=RC
time it takes to get to 63% of ss value
big C so slow build up
Big R large charge requiered to change

Question 23

cable theory

Answer 23

larger diameter and more myelination makes more efficient conductor

Question 24

TTX

Answer 24

blocks Na channels

so no depolarization

Question 25

TEA

Answer 25

block K voltage gated so no repolarization