Module 6.1 - Revisiting the Circuit diagram of the excitable cell Flashcards
In the simplified cell circuit diagram, what does addition of positive charges (Na+) by the ENa battery onto the inner leaflet of the membrane do to Vm?
Makes Vm more +
In the simplified cell circuit diagram, what does addition of positive charges (K+) by the EK battery onto the outer leaflet of the membrane do to Vm?
Make Vm more -
What does the ENa battery do?
Continuously charges Vm until it has an equal and opposite voltage
What is required for current flow from the ENa battery onto the Vm capacitor? Where does this come from?
Conductance (GNa)
Na+ leak channels
What is the simplified cell circuit diagram referred to as?
An RC circuit
Why is the simplified cell circuit diagram called an RC circuit?
Has at least one battery, one resistor and one capacitor
What are GNa and GK at rest defined by?
Population of Na and K leak channels expressed at the cell membrane
Which is larger at rest, Gk or GNa?
GK
What are the two caveats to using the GHK equation to conceptualize what happens during cellular excitation?
- GHK equation does not work when dealing with fast Vm changes
- GNa and GK change very quickly during an action potential
Why does the GHK equation not work when dealing with fast Vm changes?
Capacitors take time to charge. Thus, while conductances can change rather quickly, their effect on Vm does not happen instantly but takes time depending on the size/shape of a neuron.
What causes excitatory potentials?
Temporary rise in GNa
What causes inhibitory potentials?
Temporary rise in GCl
What can cause temporary rises in GNa?
Synaptic glutamate or acetylcholine receptors/channels that conduct Na
What can cause temporary rises in GCl?
Synaptic GABA, Glycine receptors that conduct Cl-
What causes action potentials?
Temporary rise in GNa followed by a rise in GK.
