2nd week 1 Flashcards
Resting membrane potential:
Voltage difference across the membrane of a neuron when it is at rest (non-signalling)
Intracellular -70 mVs, (compared to extracellular 0mV)
Concentration gradient:
Positive or negative ions is higher/lower in one area than another.
Depolarisation:
A change in a neurons membrane potential that makes it more positive (less negative).
Hyperpolarization:
A change in a neurons membrane potential that makes it more negative. It is the opposite of depolarization.
Ionotropic receptors:
Transmembrane proteins that form a channel allowing ions to travel in/out of a cell.
These channels are opened when the receptor binds a ligand, like a neurotransmitter.
Glutamate receptors and GABA A receptors are examples of ionotropic receptors.
Voltage-gated ion channels:
Transmembrane proteins that form ion channels whose opening and closing is regulated by the membrane potential near the channel.
What types of electric activity:
hints
- up to 700-600volts (one 120mV)
- -70 mV (-80 to -60mV) present in most neurons
- 1 - 40 mV small variable changes
- 100 mv, fast, all or nothing
Large voltages generated by animals
(electric eels or rays: electroplaque)
Negative resting membrane potential
(most neurons)
Postsynaptic potentials
(small variable changes in membrane potential)
Action potentials
(large, fast, all or none fashion)
Explain functioning of an electroplaque
An electroplaque has Na/K pump maintaining membrane potential, operates on ATP.
When acetylcholine binds (ionotropic ligand gated) to nicotinic Ach receptor nAchR, sodium (Na+) flows in. depolarisation 120 mV.
Has electroplaques piled up, can create a shock up to 700V (volts)
concentration/electrical grade
draw directions
EPSPs are generated by activation of ion channels that let ….. ions into the cell –> …polarise neurons.
IPSPs are generated by activation of ion channels that let …. ions into the cell –> …polarise neurons.
EPSPs are generated by activation of ion channels that let positive ions into the cell –> depolarise neurons.
IPSPs are generated by activation of ion channels that let negative ions into the cell –> hyperpolarise neurons.
EPSPs and IPSPs are:
- graded in amplitude due to the ….. of neurotransmitter and …. the neurotransmitter is in the synaptic cleft
- additive, but decay in …. as they move around the neuron
concentration and length of time the neurotransmitter is in the synaptic cleft
amplitude
describe what happens to Nav and Kv (sodium and potassium gates) in
a) resting Vm
b) upstroke
c) peak
d) downstroke
e) resting Vm
Nav and Kv
a) closed, closed
b) open, closed
c) closed inactive, starts open
d) closed inactive, open
e) closed, closed
Electroplaque
Vm rest
PSP
AP
size
recorded from outside the cell
generated by ionotropic ion channel receptors (NT)
generated by voltage-gated ion channels
duration
graded
Field potential:
Electric potential in the extracellular space around neurons.
Nerve:
Nerve: a bundle of axons.
Compound axon potential:
Compound axon potential: the sum of the activity in a number of nerve fibers [axons].
Extracellular recording (ER):
(5 types)
- field potentials
- whole nerve activity
- multi-unit activity
- single unit activity
- multi-electrode arrays (MEAs)
Intracellular recording (IR):
(3 types)
- activity within single cells
- sharp electrodes
- patch suction electrodes
Single channel recording (SCR):
(2 types)
- recording activity of single ion channels
- patch clamp-type electrode
Extracellular recording (ER)
- the electrode is xxxside but close to the xxxx
- the electrodes pick up only xxxx potentials and xxx frequency filtered action potentials
- it is not possible to record xxx or post-synaptic potentials
- the electrode is outside but close to the neurons
- the electrodes pick up only field potentials and low frequency filtered action potentials
- it is not possible to record Vm rest or post-synaptic potentials
Example of recording field potential in mouse hippocampus, tri circuit
Stimulating electrode in tissue, Schaffer collaterals.
When stimulus given, activates Sch collaterals –> release of NT onto purkinje neurons in the area of CA1.
One electrode records the fEPSP and another sum of many AP of CA1 neurons = somatic population spike.
O’keefe & Nadel (1978); The Scripps Research Institute (2008)
Give an example of recording compound AP
Whole nerve recording
Frog sciatic nerve
Maximum capacity can be recording, adding voltage over hat won’t change the curve of an AP.
Mark CNS end, place on a dish over stimulating an recording electrodes. Apply olive oil at the ends, ringer in the middle (ions). Silicon grease between containers [conductance all the way through]
Lilley & Robbins (1998)
Rattus rattus has been used to separate different axons in the vagus nerve by measuring xxxx of the stimulus and their xxx xxxx.
Dochery et al. 2005
Rattus rattus has been used to separate different axons in the vagus nerve by measuring the intensity of the stimulus and their conducting velocity.
Multi-unit extracellular recording
- can de done in vivo?
Give an example
- rat LGN
yes
Electrode in rat brain, lateral geniculate nucleus.
Flash of light
Measures the neuron closest by but a neuron further away. Simultaneously measuring two neurons.
Human single-unit recording
This experiment shows that xxxx neurons may exist in human brain.
A human (with DBS electrode) gave consent to a single-unit recording.
Was shown pictures of Halle Berny, neuron showed activity. A picture of Michelle Pfeiffer didn’t cause a reaction.
Association neurons
Quiroga et al. 2009
Multi-electrode arrays MEA
how many electrodes
Is it inert to cells?
What kind of activity does it pick up?
64
yes, it doesn’t bug them. Cells can happily grow on it. non invasive
Extracellular activity [outside the axons]
What [divices] are used for intracellular recordings?
current clamps
voltage clamps
sharp electrodes
patch clamps electrodes
Voltage
potential difference between two points
Current
Ciona intestinalis (sea squirt)
recording Oocytes, sharp electrodes, intracellular recording
- To record voltage, what clamp is used?
- to record current, what clamp is used?
- sharp electrode current clamp
- Sharp electrode voltage clamp
Perezoso, 2007
Patch clamp electrode:
- cell-attached patch recording?
- whole cell clamp?
- inside out patch, outside out patch?
- perforated patch?
- cell-attached patch recording:
pipette forms gigasel on the cell membrane, measures single-cell activity.
- whole cell patch:
inside the cell records all ion channels
- inside out patch, outside out patch:
possible to record single ion channel activity
- perforated patch:
using antibiotics to pore wholes
What technique can be used to measure intracellular calcium?
Number of action potential is related to the entry of … in the cell.
Whole cell patch clamp in current mode.
calcium
Can a single ion channel be recorded?
Yes, by using patch clamp electrode
[remember pipette, air pressure etc.]
yes/no
extracellular recording - humans(in vivo) / non-humans (in vivo) / in vitro (human tissue)
intracellular recording - humans(in vivo) / non-humans (in vivo) / in vitro (human tissue)
Single cell recording - humans(in vivo) / non-humans (in vivo) / in vitro (human tissue)
yes (as a part of treatment like DBS) / yes (implanted,anaesthetic) / yes
no / yes (anaesthetic=kept still) / yes
no / yes (anaesthetic=kept still) / yes
advantages / disadvantages current clamp?
A
Records activity of the cell in ‘physiological conditions’ Detailed and high resolution recordings of voltages
D
Can’t control voltage
advantages / disadvantages voltage clamp?
A
Can control the voltage
Detailed and high resolution recordings of currents
D
unstable
advantages / disadvantages sharp electrode?
A
reusable, simple electrode solution
D
High resistance
Can be difficult to make
Some damage to the cell
advantages / disadvantages patch electrode?
A
Low resistance
Relatively easy to make
Less damage to cell
Dialysis of cell contents
D
Not reusable
Dialysis of cell contents
Complex electrode solution
advantages / disadvantages single channel?
A
Allows the recording in real time of the functional activity of a single protein
Elucidates drug action at molecular level
D
Complex and lengthy analysis
Electrophysiology can record the electrical activity of whole brain xxx, a xxx neuron or a single ion xxx.
Electrophysiology can record the electrical activity of whole brain tissue, a single neuron or a single ion channel.
Electrophysiology is a dynamic, functional, SI unit-based, real-time, hi-fidelity and high xxx resolution approach.
temporal
Many electrophysiological approaches can be used in xxxx.
vivo
Electrophysiology can be used simultaneously or in xxxxx with optical, molecular, biochemical and pharmacological techniques.
Electrophysiology can be used simultaneously or in conjunction with optical, molecular, biochemical and pharmacological techniques.
