L7 - techniques - electrophysiology and functional imaging Flashcards
intracellular electrophysiology used to study….
electrical activity in single cells
extracellular electrophysiology used to study…
electrical activity from groups of cells in one anatomical location
functional Ca2+ imaging used to study…
electrical activity from groups of cells in a larger anatomical area
electrophysiology
measures electrical activity (membrane potential) in biological tissue
membrane potential
potential difference between an electrode inside a cell and an electrode outside a cell
intracellular component is ….. charged compared to extracellular
negatively
what causes difference in intra/extra-cellular charges
difference in K+ concentration
K+ is more concentrated….
inside cell
K+ leak channels
allow K+ to flow freely across membrane and leave cell
therfore inside is more -ve
what creates equilibrium
chemical and electrical gradients in opposing directions
3 different methods of preparation for measuring neuronal electrical changes
- dissociated neuronal culture
- acute brain slices
- whole animal
dissociated neuronal culture
take neurons from embryo and dissociate into parts
plate on cover slips so they grow into networks
action potentials require cells to have….
negative resting membrane potential
example of wide diversity in shapes of action potentials
purkinje neuron AP very tall steep thin
dopamine neuron more like a hump
features of hippocampal CA1 pyramidal neurons
glutamatergic
longer AP
features of O-LM interneuronsq
GABAergic
shorter AP
what are phase plane plots for
give information on max rate of rise and max rate of fall of action potential
and AP peak
calculations of rate of rise/fall
dv/dt
what determines the peak of the AP
Na+/K+ currents
how do you measure ionic currents
using voltage clamps
what mediates ionic currents
channels
single channel recordings open/close …
stochastically
V1/2 activation
size of current against test potential
expressing a-subunit with B-subunit causes….
x2
- shift in voltage dependance of Na+ currents
- a-subunits form pore for Na+ channel
rebound event
cell is pushed back towards resting membrane potential
AHP
after-hyperpolarisation
large AHP
high frequency firing
3 states of channels
resting
activated
inactivated
channel in resting state
closed
ability to open
-ve potential
channel in activated state
open
depolarised
inward current
channel in closed state
unable to open
recovering from activation
why can interneurons fire more quickly
they recover more quickly
recovery time from activation requires ….
x2
time
-ve membrane potential
when does high frequency burst firing occur
if after-depolarising hump is big enough it will reach threshold potential
another AP can be initiated
Kv3 subtypes expressed by interneurons
produce large post-spike AHP
this allows fast repolarisation and quick recovery
are firing patterns fixed?
no
what modulates firing patterns
membrane potential developmental stage disease - channelopathies pharmacological agents synaptic actiivty intrinsic activity - affected by neurotransmitters
EPSP
excitatory post synaptic potential
