Ion channels and action potential Flashcards
Always open and allow ___ to passively diffuse down concentration gradient (out of cell)
K+ Leak channels
Always open and allow ___ nto passively diffuse down concentration gradient (into cell )
Na+ leak channels
open when threshold is reached and allows Na+ influx
Voltage Gated Na+ Channels
Open around peak of action potential and allow K+ efflux
delayed recitifier voltage gated K+ Channel
RMP (-70 mV)
K+ makes a bigger contribution to establishing the RMP than Na+
Depolarization
amount of Na+ entering cell is greater than the amount of K+ leaving cell through K+ leak channel, so nerve interior becomes increasingly positive and depolarizes
threshold
voltage the membrane potential must increase to in order for an action potential to occur
Peak
Membrane potential of nerve peaks near Nernst potential of Na+. Voltage gated Na+ channels close
and Delayed Rectifier Voltage Gated K+ Channel opens. Na+ stops flowing into cell and K+ starts
flowing out of cell through leak channels and Delayed Rectifier V-Gated K+ channel. Cell interior stops
becoming increasingly positive and instead starts to become negative as K+ leaves cell
Repolarization
Only channel open is Voltage Gated Delayed Rectifier K+ channels, so cell interior is
getting increasingly negative as amount of K+ flowing out > amount of Na+ flowing in
Undershoot
Delayed Rectifier K+ channels are slow to open and close, so membrane potential dips
slightly below RMP as K+ continues to flow out of cell as gate on Delayed Rectifier K+ channel slowly
closes (Results in hyperpolarization)
voltage clamping
technique that enables you to hold the membrane voltage of an excitable cell at a fixed voltage while you measure the current passing through the cell membrane
current =
Conductance * Voltage
if there is an inward and outward current, ions must be moving in and out of the ___
neuron
how do we know which parts of the current curves are due to the movement of Na+ or K+
TTX- toxin by puffer fish block Na+ channels
TEA : selectively blocks potassium channels
above the y axis corresponds to ____ ions leaving the cell
positive
Na+ channels open __ and open ___
first and quickly
K+ channels open ___ and ___
after and slowly
hold voltage constant and measure change in current
Voltage clamp
hold current constant and measure change in voltage
current clamp
same principle as voltage clamp but measures the current in a single channel at fixed voltage
patch clamp
depolarization
Depolarization, in biology, refers to a sudden change within a cell, during which the
cell undergoes a dramatic electrical change. Most cells, especially those that compose
the tissues of highly organized animals, typically maintain an internal environment
that is negatively charged compared to the cell’s surrounding environment. This difference in charge is called the cell’s membrane potential. In the process of depolarization,
the negative internal charge of the cell becomes positive for a very brief time. This shift
from a negative to a positive internal cellular environment allows for the transmission
of electrical impulses both within a cell and, in certain instances, between cells. This
communicative function of depolarization is essential to the function of many cells,
communication between cells, and the overall function of an organism.
open and close fast (slope is greater )
Voltage gated Na+ Channels
