Neuronal Excitability Flashcards
What does the Na+ gradient facilitate?
solute uptake or extrustion
What does the K+ gradient facilitate?
solute extrusion
classify the following as primary or secondary active transporters:
- Na-K-ATPase
- Na-Ca-antiporter
- K-Cl-cotransporter
- pH control antiporter
primary: Na-K-ATPase
secondary: antiporters and cotransporters
TRUE or FALSE: the cell membrane is permeable to both protein anions and potassium ions.
FALSE: impermeable to protein anions
What are the 2 forces that contribute to the electrochemical gradient?
chemical (concentration) force and electromotoric (potential) force
Which equation is used to calculate the equilibrium potential of an ion?
Nernst equation
Why is Vm close to Ek?
glial cells have a very high resting conductance (ease with which ions can flow across the membrane)
What is the Nernst equation used for?
determination of equilibrium potential VIA ION GRADIENT
Why does the overshoot of an AP not reach +60 mV?
Na+ channels close and
label conductance for slide 4 in the diagram and describe events of an AP (i.e. recreate the diagram and label)
see slide
When are the leak K+ and Na+ channels open?
always open
What is the threshold potential?
-40 mV
What is the diagram on the right of slide 6 demonstrating?
although current injected increases suprathreshold, the action potential elicited spike the same –> this implies that APs are an all-or-none response
Where on an axon are majority of the V-gated Na+ channels located? What does the location imply about AP generation?
at the axon hillock –> therefore APs are generated closer to the soma than the dendrites
Why was the patch-clamp technique originally developed?
to prove that ion channels exist and a very small current flow can be measured, even through a single activated channel
draw the current of an AP in control, TEA and TTX conditions
What is the effect of administering TEA on ion channels? TTX?
- TEA blocks V-gated K+ channels
- TTX blocks V-gated Na+ channels
Explain the reversal of voltage-gated Na+ channels. Which drug can be used to demonstrate this?
- depolarizations in the negative Vm range induce increasingly large inward Na+ current
- depolarizations in the positive Vm range makes the Na+ current amplitude SMALLER until it reaches zero at +60 mV
- TEA
draw the mechanism of an EPSP (consider NTs and ions and receptors).
How is depolarization caused?
- NT: glutamate
- ions: Na+, K+
- receptor: glutamate receptor on cation channel
- Na+ influx (conductance) greater than K+ efflux –> depolarization
draw the mechanism of an IPSP (consider NTs and ions and receptors).
How is hyperpolarization caused?
- NT: GABA
- ions: Cl-
- receptor: GABA(A) or glycine receptor on anion channel
- Cl- conductance greater than K+ conductance –> hyperpolarization
