Exam 2 Powerpoint 8 Flashcards
Sodium potassium pump
3 Na + out 2K+ in
In neurons, how does the
increase in sodium permeability
occur during the Action
Potential?
Voltage gated sodium channels, open at threshold
Voltage gated K channels are important at
falling phase
Is permeability voltage dependent?
yes
Inward current
Early
Transient(comes and goes)
Fast
Na+
+ charge enters
Outward current
Late
Sustained
Delayed
Slow
K+
+ charge leaves
Current flow across a membrane is sensitive to
membrane voltage
There are____different types of voltage dependent ion currents
2
How could researchers tell that Na+ and K+ were responsible
they changed to concentration of those ions
TTX (tetrodotoxin)
Puffer fish, skin of frogs, and salamanders
Blocks Na+ channels
TEA: tetraethylammonium
Large organic cation
Blocks K+ channels
The solutions of the body (solution inside and outside cells)
are ____________, and they will therefore conduct electricity
ionic solutions
Membrane potentials are voltages, which ______________ made
up of the movement of ions
drive currents
Ions can cross membranes through ion channels, the resistance being smaller the _______________________
more channels are open
We can therefore use Ohm’s law to predict how much current
would flow when the ion channels opened, if we knew the
_____________- (the voltage across the membrane) and
the ___________ of the membrane to the passage of the ions.
membrane potential
resistance
Number of open channels is called ____________
permeability
Vdf=
Vdf= (Vm – Erev)
Iion =
Iion = gion * (Vm – Erev)
There are two factors for an ion
that determine how much influence that ion will have over the membrane potential of a cell
◦ That ion’s driving force and,
◦ That ion’s permeability
A positive driving force (i.e., VDF > 0) predicts ion movement ___________________
out of the cell
A negative driving force (i.e., VDF < 0) predicts ion movement _______________
into the cell
