Ion Channels II Flashcards
Explain the neuronal action potential.
1) Depolarising input take membrane potential to a threshold level.
2) Sodium channels sensitive to voltage open.
3) Sodium channels conduct less as they inactivate.
4) Potassium channels sensitive to voltage open.
5) Potassium channels to voltage close.
What is the difference between the response times in sodium channels and potassium channels?
Sodium channels RESPOND FAST (BRIEF RESPONSE).
Potassium channels RESPOND MORE SLOWLY.
Where are voltage - gated sodium channels found?
Found in neuronal / skeletal / cardiac cells.
What are the 2 key distinct features of voltage - gated sodium channels?
Rapid opening upon depolarisation.
Exhibits distinctive inactivation.
What type of graph does a voltage sensor create?
Hydropathy Plot.
Where is the fat liking part of the cell found?
Found on the inside of the cell.
Where is the water liking part of the cell found?
Found on the outside of the cell.
Why is the 4th transmembrane protein special?
Special for its gating = Known as a voltage gated sensor.
What is the name of this voltage sensor and what is its function?
S4 voltage sensor = Detects when to open and close the gated mechanism.
How does inactivation occur?
Shape change occurs and then a a tray known as a T- Tray becomes inactivated.
This prevents the flow of ions.
Which voltage gated channel is larger?
Sodium channels are LARGE than potassium channels.
x4 times LARGER.
Which molecules are K channels permeable to?
K+ / Rb+ / NH4+
Why does K+ pass through at such high rates?
Combination of high selectivity and rapid throughput.
What are voltage gated sodium channels blocked by?
Local Anaesthetics and Tetrodoxin.
What is the main structure of voltage gated sodium channel?
1 protein with 4 very similar domains each with 6 transmembrane sections.
What is the main structure of voltage gated potassium channel?
4 proteins each with 6 transmembrane sections.
What are voltage gated potassium channels blocked by?
Many drugs
What is the sodium flow timing?
2 - 4 ms (2000th of a sec).
What is the potassium flow timing?
10 - 100s of ms.
Where is voltage gated sodium channel activity modulated?
Nerves / Skeletal Muscle / Heart
Where is voltage gated potassium channel activity modulated?
Nerves / Heart / Smooth Muscle
What is the activation like regarding voltage gated sodium channels?
Inactivates rapidly.
What is the activation like regarding voltage gated potassium channels?
Inactivates quickly / slowly / not at all.
What is the opening of the channel like with voltage gated sodium channels?
Opens rapidly once a threshold is reached.
What is the opening of the channel like with voltage gated potassium channels?
Opens slowly once a threshold is reached.
