Electrophysiology

Front 1

membrane properties

Back 1

hydrophilic head

hydrophobic tail

selectively permeable

contain membrane bound proteins

Front 2

membrane functions

Back 2

compartmentalise

transport across membrane

Front 3

membrane thickness

Back 3

10 nm

Front 4

types of transporters

Back 4

uniport

symport

antiport

Front 5

types of membrane transport

Back 5

simple diffusion

channel mediated diffusion

carrier mediated diffusion

active transport

Front 6

nature of leakage channels

Back 6

always open

Front 7

nature of gated channels

Back 7

opening probability increased by

stimulus energy

Front 8

importance's of electrical phenomena to cells

Back 8

membrane potential is biggest controller of ions and molecules

osmotic balance

ion flow controls fluid flow

sensory signalling

force generation`

Front 9

describe importance of membrane potential in transport epithelia

Back 9

Na diffuses into cell from lumen

Na/K on basolateral expels 3Na and imports 2K

positive charge builds in IF due to Na/K inbalance

positive charge attracts Cl from lumen

flow of Cl ions increases osmolarity and draws fluid from lumen to IF

Front 10

how is Rm established

Back 10

trapped Organic anions

Na/K pump

high permeability to K

Front 11

describe how selective permeability to K establish Rm

Back 11

Na/K pump builds up intracellular K

K can diffuses out of cell due to high permeability down gradient

K efflux causes a net negative charge to build up inside cell

K efflux (diffusion) and influx (electrostatic) balance to give negative Rm

Front 12

concentration change due membrane voltage generation is ____________

Back 12

small

Front 13

describe electrochemical equilibrium

Back 13

point where the Force moving an ion down a chemical gradient is equal and opposite to the force moving it down its electrical gradient ,thus no net movement of the ion

Front 14

charge formula

Back 14

Q = znF

Front 15

ohms law formula

Back 15

V=IR

Front 16

describe ohms law

Back 16

describe relationship between voltage current and resistance

Front 17

resistance of pure phospholipid bilayer

Back 17

10^15 Ohms/cm

Front 18

relationship between conductance and resistance

Back 18

G=1/R

Front 19

define charge

Back 19

imbalance between # of positive and negatively charged particles

Front 20

define Faradays constant

Back 20

charge on 1 mol of protons

Front 21

define conductance

Back 21

ease with which electrical current passes

Front 22

define resistance

Back 22

quantitative measurement of how substance reduces the flow of electrical current through it

Front 23

membrane capacitance

Back 23

1 micro F per cm^2

Front 24

define capacitance

Back 24

capacity to store opposite charges on plates separated by insulating layer

Front 25

relate voltage to capacitance

Back 25

voltage generated is proportional to charge separated and inversely proportional to the capacitance

Front 26

capacitance symbol

Back 26

C

Front 27

conductance symbol

Back 27

G

Front 28

voltage developed across layer = _____

Back 28

Q/C

Front 29

what determines capacitance

Back 29

mutual attraction of charges

di-electric constant of membrane

- membrane area (A)

- membrane thickness (a)

Front 30

C equation

Back 30

C= (di-electric constant*A)/a

Front 31

describe the size of the change to generate membrane potential

Back 31

very small amount of ions/charge needs to move to generate potential

no effect on concentration

Front 32

what drives ion movement across a membrane

Back 32

electrochemical potential difference

Front 33

electrochemical potential difference formula

Back 33

RTln([x]in/[x]out) + zxF*(Voltage difference across membrane)

Front 34

describe Nernst equation

Back 34

at equilibrium chemical pot. - electrical pot. = 0

Front 35

nersnt equation function

Back 35

shows the Vm that would need to exist for ion to be at equilibrium (Ex)

Front 36

Ex depends on ____

Back 36

valence

temperature

chemical gradient

Front 37

describe net flow

Back 37

net flow of ions due to chemical/electrical potential

Front 38

net flow formula

Back 38

Ix = Gx(Vm-Ex)

Front 39

Gx is _____

Back 39

total membrane conductance to ion x

Front 40

Gx factors

Back 40

1 # of channels open

2 # of available ions

3 how easily the ions pass

Front 41

IV curve purpose

Back 41

show relationship between ion flow (current) and membrane potential

Front 42

slope of IV curve shows

Back 42

conductance

1/resistance

Front 43

reducing the resistance will make an IV curve _____

Back 43

steeper

Front 44

define in vitro

Back 44

artificial cell free systems

Front 45

define in vivo

Back 45

real cell systems

Front 46

example of an in vitro system

Back 46

planar lipid bilayer

Front 47

describe planar lipid bilayer

Back 47

small hole in substance seperating two solutions has membrane painted over it, mimics real lipid bilayer

Front 48

lipid bilayer pros

Back 48

can control channel composition of membrane

can control solution on either side of membrane

Front 49

lipid bilayer cons

Back 49

not a real cell

Front 50

describe glass micropipette electrode

Back 50

thin glass tube containing electrolyte solutino and an electrode, has sharp open tip

Front 51

micropipette cons

Back 51

alot of noise

high electrical resistance

Front 52

micropipette pros

Back 52

allows intracellular recording by penetrating cell membrane

Front 53

what is required for a diffusion potential

Back 53

no complex intracellular machinery only gradient

Front 54

describe findings of squid axon experiment

Back 54

expelling axoplasm and filling with artificial solution showed that Vm was dependent on presence of K+ only

Front 55

relationship between metabolic energy and diffusion potential

Back 55

experiments blocking ATP production showed it had no effect on Rm and therefore diffusion potential doesnt depend on metabolism

Front 56

describe relationship between K+ concentration gradient and diffusion potential

Back 56

almost linear relationship between extracel. K+ and Vm

Front 57

describe voltage clamp method

Back 57

current is injected into the cell causing predictable step change in Vm, when the Vm deviates from the "command: Voltage further current is injected until Vm remains constant, when Vm is constant the current added is equal and opposite to the total membrane current Im

Front 58

describe a patch electrode

Back 58

a glass micropipette with blunt ends that do not impale membrane but rather grab

Front 59

describe patch clamp setup

Back 59

patch electrode grabs and pulls a section of membrane containing 1 channel into the pipette without detaching

Front 60

patch clamp pros

Back 60

allows measuring current through a single channel

Front 61

describe a rupture patch setup

Back 61

same as patch clamp except more suction is added which splits apart ion channel connectiong patch electrode with cytoplasm directly

Front 62

modes of patch pipette

Back 62

cell attached (patch clamp)

whole cell (rupture patch)

Front 63

define macroscopic currents

Back 63

sum of multiple single channel currents

Front 64

relationship btwn macroscopic current and single channel current

Back 64

macroscopic current is a stepped multiple of the single channel current according to the # of channels present

Front 65

define discreet current

Back 65

current through a single channel

Front 66

describe rltshp btwn discreet current and voltage

Back 66

discreet current size steps with voltage,,

Front 67

slope of IV plot of single channel shows

Back 67

unitary conductange