Electrophysiology Flashcards
What are the effects of IPSPs?
How can an IPSP be both depolarising and hyperpolarising?
The change in potential difference during an IPSP will always be on the ‘hyperpolarised side’ of the threshold potential. In other words the reversal potential will be more negative than threshold.
If Vm > Ecl, it will be hyper polarising
If Vm < Ecl, it will be depolarising … BUT the potential still gets held above threshold.
What is the time scale of AP…
a) Generation?
b) Conduction?
a) fastest = 2ms (whole AP generation including the refractory period)
b) ranges from <1m/s to 100m/s; but generally 10m/s
What’s the difference between intracellular and extracellular recording?
Intracellular
- Pierce one electrode into the cell, with an extracellular reference electrode.
- Records voltage difference across the membrane.
- Can record sub threshold changes in Vm and spikes.
- Can cause considerable membrane damage.
Extracellular
- one electrode near the cell of interest with the reference elsewhere in the EC space
- Records the voltage changes at the membrane surface.
- Only records the occurrence of spikes
- Systems electrophysiology relies heavily on this.
Where are APs generated and why?
Axon hillock, as this has the greatest density of VGNaCz
Give 4 examples of graded potentials.
Receptor potentials
Post synaptic potentials
Pacemaker potential
End plate potentials
Decide whether the statement applies to graded potentials, APs or both.
a) the stronger the stimulus, the greater the amplitude
b) the stronger the stimulus, the greater the intensity
c) spread locally via electronic spread
d) actively regenerated
e) summate
f) voltage dependent conduction
g) decremental
a) graded
b) AP
c) graded
d) AP
e) graded
f) AP
g) graded
What are non spiking neurons?
What property is most important for their functioning?
Neurons in which graded potentials can spread passively to the synaptic membrane and modulate NT release.
Very short distance from the site of the graded potential to the output synapse –> a very short axon.
What is synaptic integration?
Which potentials exhibit this property?
The addition of spatial and temporal summation over any (brief) time window to determine the value of Vm.
If Vm > AP threshold, an AP is generated.
PSPs.
What is Ex?
What will Vm be in a 1 ion system?
What is the driving force with respect to equilibrium potentials etc?
The membrane potential at which there is no net flow of ion x across the membrane.
Ex, where x is the ion present in the system.
The difference between an ions equilibrium potential and the membrane potential at any given time.
What is the reversal potential?
What property/factor dictates it’s value?
How does this relate to grading signal intensity?
It is the equilibrium potential for the ion carrying the current, when there is no net flux.
For a mixed ion current it will be a compromise - for e.g. between the values for Ek and Ena.
The relative membrane permeability to each ion. The more permeable a membrane is to a particular ion, the more influence that ion will have on Vm.
Maximum change in the membrane potential is the difference between reversal potential and rest: this is the range over which Vm can vary to code stimulus intensity.
How do thermoreceptors adapt?
Thermal adaptation occurs over a relatively large range of skin temps.
The further outside the range the skin temp is the more painful it becomes. The point where it becomes painful is due to triggering of primary afferent nociceptors with thermosensitivity.
What is the role of a TRP (thermal receptor potential) channel in thermosensation?
TRPV1 and 2are transducers of noxious heat.
- TRPV1 >43 degrees (and also lower temps when sensitised by inflammatory mediators) and also capsaicin
They all operate over a specific temperature range.
Schepers and Ringkamp 2010
