Hodgkin-Huxley Flashcards
Explain voltage gated channels?
Ion channels whose conductance varies as voltage varies.
They are ion selective: only sodium ions can pass through a sodium gate, only potassium ions through a potassium gate.
Potassium is a _______ channel. Generally, it has _____ type of open gate and _______ type of closed gate.
Persistent
one open
one closed
The potassium gate is composed of how many independent subgates?
Four.
All of which must be open to allow potassium to pass through.
gk = gkbar * n^4
What explain these terms
n = probability of a subgate being open
gkbar = conductance if the gate was open
gk Is like the utility of the gate, probability of reward*reward.
What is the name given to a sodium channel?
transient channel, it has two close states and one open.
Give the dynamics of a sodium channel during a spike
The same gate reconfigures itself
closed (1) —–> open ——> closed(2)
Closed(1) is different to Closed(2)
What do we know about closed 1?
It contains three subgates, with probability of being open called m.
What do we know about closed 2?
Not made up of subgates, the probability of the whole gate being open is h.
How does n vary with voltage?
Low voltage = near 0
High Voltage = near 1
How does m vary with voltage?
m increases as the voltage approaches the threshold
generally, m increases as voltage increases.
How does h vary with voltage?
Low voltage = near 1
High voltage = near 0
What is the difference between how the transient and persistent gates work?
Persistent channels open if voltage rises.
Transient channels also open after an increase in voltage, however they close again soon after.
does Tm depend on the value of V?
No, remember Tm is always very small
What is the significance of Tm being a very small constant?
m is always near its asymptotic value (1).
Explain what causes the rapid upswing seen in a spike?
Once sodium gates open, sodium flows in, increasing the voltage, open even more gates.
This multiplier effect explains the exponential shape to the start of a spike.
