L7 - techniques

Question 1

electrophysiology

Answer 1

measuring electrical activity of biological tissue

Question 2

potential difference

Answer 2

measured between electrode inside and outside of cell

Question 3

what causes -ve intracellular charge

Answer 3

high K+ concentration inside cell

K+ leaves cell via K+ leak channels

Question 4

3 methods of preparation for measuring electrical changes to neurons

Answer 4

1 - dissociated neuron cultures
2 - acute brain slices
3 - whole animal

Question 5

dissociated neuron cultures method

Answer 5

plate fragments of neurons from embryos and add growth medium so they grow into networks

Question 6

advantages of dissociated neuron cultures

Answer 6

easily accessible for recording
cells well isolated
easy to carry out

Question 7

disadvantages of dissociated neuron cultures

Answer 7

only good for embryos

not normal physiological environment for neurons

Question 8

acute brain slices methods

Answer 8

record from neurons in thin slices of brain tissue

Question 9

advantages of brain slices

Answer 9

local circuits remain intact
carry out at any developmental stage
easy to identify specific regions

Question 10

disadvantages of acute brain slices method

Answer 10

long range inputs/outputs get cut

not normal physiological environment

Question 11

whole animal method

Answer 11

animal under anaesthesia
implant electrodes
recordings made when animal is awake

Question 12

advantages of whole animal recordings

Answer 12

all circuits remain intact

allows correlation of electrical activity wth behaviour

Question 13

disadvantages of whole animal recordings

Answer 13

difficult to carry out

Question 14

2 ways of intracellular recording membrane potential of a neuron

Answer 14

sharp electrode

patch clamp recording

Question 15

sharp electrode method

Answer 15

electrode made of glass
filled with solution similar to that of the cell
very high resistance - narrow tip
poke a hole in side of cell
allows access to record membrane potential relative to outside the cell

Question 16

patch clamp recording

Answer 16

more modern/popular method
lower resistance pipette - wider tip
put on surface of membrane
apply negative pressure (suction)
bursts membrane under pipette
cytoplasm continuous with inside of pipette allows access for recording

Question 17

equipment required for intracellular recordings

Answer 17

whole set up = rig 
placed on anti-vibration table
microscope
manipulators
big metal cage

Question 18

how do you isolate pipette from external vibrations

Answer 18

rig placed on anti-vibration table

Question 19

what is the microscope for

Answer 19

visualising individual neurons within the brain slice

Question 20

what are the manipulators for

Answer 20

very delicately place the glass pipette onto the surface of the cell

Question 21

what is the big metal cage for

Answer 21

surrounds the rig

isolates rig from ambient electrical noise

Question 22

amplifer

Answer 22

takes small analogue/electrical signal and makes it larger

converted to digital signal before being sent to computer

Question 23

why is saline solution used

Answer 23

similar to csf

Question 24

cell attached recording

Answer 24

pipette attached to membrane via small suction
doesnt break through surface
low resistance seal

Question 25

whole cell recording

Answer 25

more suction/negative pressure applied membrane bursts underneath pipette allows electrical access to inside of cell

Question 26

inside out patch

Answer 26

suction from whole cell recording pulls small bit of membrane from underneath pipette and separates from cell allows recording of individual ion channels

Question 27

Ohm's law

Answer 27

``` V= I x R voltage = resistance x current ```

Question 28

low resistance occurs when

Answer 28

lots of ion channels are open

Question 29

how do you make current clamp recordings

Answer 29

inject different currents to stimulate the cell to give the resistance of the membrane

Question 30

why do you apply different drugs in current clamp recordings

Answer 30

drugs alter the ion channels of membranes | causes changes in resistance of membrane

Question 31

describe the EPSP of a CA1 pyramidal neuron

Answer 31

fast rising | slow decaying

Question 32

what are voltage clamp techniques for

Answer 32

they fix the voltage so it cant change | allows studying of underlying currents

Question 33

the amplifier injects -ve current to maintain cell at -80mV...

Answer 33

the cell cant depolarise | opposes +ve ion flow via glutamate receptors

Question 34

EPSC stands for

Answer 34

excitatory post synaptic current

Question 35

what is an epsc

Answer 35

the flow of ions that causes an epsp

Question 36

as +ve ions move into the cell what happens to the extracellular space

Answer 36

becomes more -ve

Question 37

advantages of measuring extracellular space

Answer 37

does not disrupt intracellular content can record spikes in vivo can record many cells at once

Question 38

what causes the size of the extracellular recording spike to vary

Answer 38

the distance of the recording from the electrodes | electrodes pick up spikes closest to them

Question 39

tetrode

Answer 39

bundle of 4 electrodes

Question 40

what does functional imaging measure

Answer 40

neuronal activity

Question 41

benefits of functional imaging

Answer 41

measures a larger anatomical area that electrodes

Question 42

gCaMP

Answer 42

calcium indicator protein | fluorescent when bound to Ca2+

Question 43

limitations of gCaMP

Answer 43

difficult to distinguish fluorescence between 6 small spikes or 1 large Ca2+ signal