electrophysiology

Question 1

what is electrophysiology

Answer 1

measuring electrical activity in biological tissue
brain, heart, muscles, eyes, cochlea, nerves, SC

Question 2

what do electrophysiological recodings measure

Answer 2

measure potential difference between inside and outside the cell
membrane potential

Question 3

What is the ionic basis for the potential difference between the intracellular and extracellular space?

Answer 3

resting membrane potential
K+ selective ‘leak’ channel
K+ ions flow across the membrane from the inside to the outside
inside of the cell to become more negative and outside to become more positive.

Question 4

chemical and electrical gradients

Answer 4

moving in opposite directions
reach equilibrium

Question 5

What are the pros and cons of using dissociated neuronal cultures to study electrophysiology?

Answer 5

+ = cell easily accessible for intracellular recoding
- = no anatomical correlate - cells not in physiological environment - only study early developmental stages

Question 6

What are the pros and cons of using acute brain slices to study electrophysiology?

Answer 6

+ = local circuits intact = can study developmental stage = anatomically relevant
- = long range inputs/outputs severed - not physiological environment

Question 7

What are the pros and cons of using whole animals to study electrophysiology?

Answer 7

+ = all circuits intact - can correlate activity with behaviour
- = technically challenging – for intracellular recordings

Question 8

how to record intracellular membrane potential

Answer 8

Starting using patch clamp recordings
ensure cell membran remains in tact
Allows current through single ion channels
Caputures by the pipette
Record activity of channel itself

Question 9

difference between using sharp and patch pipette

Answer 9

sharp = high tip resistance , pokes a hole
patch = low tip resistance , perfuses cell with pipette solution

Question 10

equilibrium potential

Answer 10

the membrane potential at which there is no net flow of ions

Question 11

what is ionic equilibrium potential determined by

Answer 11

intracellular con
extracellular con
valance of the ion

Question 12

what equation is used to measure the potential of an ion

Answer 12

Nernst equation

Ex = 61.5/z log(1) [X] out/ [X] in

Question 13

how can we control equilibrium potentials

Answer 13

controlling intra and extracellular ion conc

Question 14

what happens to the membrane potential is we open sodium channels (e.g apply channel agonist)

Answer 14

opening of sodium permeable channel = depolarisation of membrane potential

Question 15

what happens to the membrane potential is we open potassium channels (e.g apply channel agonist)

Answer 15

opening potassium permeable channel = hyper polarisation of membrane potential

Question 16

why in juvenile neurons is the conc of Cl more than resting membrane potential

Answer 16

Ecl > V(rest) = activated Cl- channels depolarise the membrane

K+/Cl- co transporter (KCC2) pump = pumps cl- ions out of the cell = contributes to E(Cl)
KCC2 not expressed early in development = so cl- conc inside is higher and Ecl is more depolarised
so activation cl- channels in early development = depolarisation

Question 17

what is Ecl like in adult neruons

Answer 17

normally Ecl < Crest = activating cl- channels hyper polarises the nearons

Question 18

KCC2 protein function

Answer 18

the K+/Cl- co transporter - pumps Cl- ions out of the cell.

Question 19

EPSP

Answer 19

excitatory postsynaptic potential
record the activity of one single neueon

Question 20

how do we use electrophysiology to study synapses

Answer 20

record activity of ion channels across membranes
ap - pre synaptic cell releases neurotransmitters - act on post synaptic receptor - ion channel - cause ion channel to open - stream of ions flow - record from post synaptic neuron

Question 21

where on the neuron would u measure EPSP

Answer 21

At the soma

Question 22

what is a field potential / fEPSP

Answer 22

as positive ions move into the cell
extracellular space becomes more negative

record the activity of the extracellular space when many synapses happens simultaneously

Question 23

intracellular vs extracellular recordings

Answer 23

intracellular = EPSP = ion channel activities
Extracellular = fEPSP = stream of ions going inside the cell

Question 24

what does current clamp measure

Answer 24

membrane potential
used to monitor the effects of manipulation (drugs) on membrane potential

Question 25

voltage clamp measure

Answer 25

records the current
used to study the underlying biophysical properties of channels in the membrane and effects of manipulation (drugs) on these

Question 26

ohms law

Answer 26

V = IR

Question 27

how do electrophysiological amplifies stimulate cells

Answer 27

injecting current
intracellular recording of voltage are called Current clamp

Question 28

what happens to membrane potential with current clamp

Answer 28

Vm = more positive as it moves towards E (Na)

Question 29

what happens to membrane potential with a voltage clamp

Answer 29

it does not change
to counteract the flow of + sodium ions into cell
amplifies injects negative current
voltage clamp monitors the in and outs

Question 30

EPSC

Answer 30

V clamp at -80mV
amplifier injects negative current to maintain the cell at -80mV to oppose the flow of + charge ions via glutamate receptor