L1 Flashcards
what is difference between transcellular and paracellular?
- transcellular - transport through cells
- paracellular - transport between cells
what is Rte?
transepithelial resistance
- how easily ions/solute crosses epithelia
what is the Rte of tight and leaky epithelium?
tight - <200 Ohms cm2
Leaky >2000 Ohms cm2
what usually is the transepithelial potential of leaky and tight epithelium?
Leaky - 0mv
Tight - ~50mV
what is the transepithelial potential?
Sum of the individual membrane potentials (apical and basolateral Vte’s can be different)
what determines the tightness of epithelia?
- Amount of paracellular transport (transcellular transport stays the same)
- leaky - lots of paracelllular transport
what could create a -Ve Vte?
- more anions or less cations in the apical space
What could creat a +Ve Vte?
- more cations or less anions in the apocal space
give some techniques used in electrophysiology
Intracellular electrose
Patch clamp
Two electrode voltage clamp
Ussing chambers
what is the nernst potential?
The membrane potential, where there is no net current acorss a membrane - determined by concentrations
what is amiloride?
A blocker of epithelilal sodium channels (usual shifts Vm in negative direction)
what happens in a patch clamp/2 voltage clamp?
Clamp cell to a potential that you wnat, this creates a driving force for ion movement - measure the current created
What can an ussing chamber measure?
- short circuit current (Isc)
- Rte
- Vte
what calculation is for Rte?
Rte = change in potential / I injected
what does Ba2+ block?
- blocks K+ channels
