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Human Neuroscience > Voltage Gated Ion Channels > Flashcards

Flashcards in Voltage Gated Ion Channels Deck (16):
1

V-Gated Ion Channels are found in the excitable membranes of which four cell types?

Neurons, Skeletal Muscle Cells, Cardiac Muscle Cells, Smooth Muscle Cells.

2

What are the three types of Voltage Gated Ion Channels and where are they found?

Na+ Cells - Nerve Cells
K+ Cells - Nerve Cells
Ca++ Cells - Synapses, Muscles

3

At what potential are Na+ Channels closed?

-60mV

4

At what potential do Na+ channels open rapidly and for how long do they remain open?

Open rapidly above -30mV
Close within 1-2 milliseconds.

5

How do V-gated Na+ channels work?

Depolarisation opens m-gates.
H-gates close the channel internally within 1-2 milliseconds.
M-gates change shape causing deactivation.

6

How do v-gated K+ ion channels work?

At -70mv K+ channels closed.
When cell depolarises to +40mV K+ channels open.
within 1-2 seconds the v-sensing m-gates close the channel again.

7

Describe the sub-units of V-gated ion channels.

Ion channels have 4 identical sub units arranged in a circle around a central aqueous pore.

8

How many alpha helixes span the membrane in each sub-unit of a voltage gated ion channel.

6

9

What is the function of the inner-most alpha helix (s2) in an ion channel.

Acts as a Voltage sensor.

10

What is the function of peptide loops linking the s5-s6 alpha helixes which line the ion channel?

Confer ion selectivity and provide targets for drugs.

11

There are intracellular, extracellular and transmembrane sites to which drugs can bind to V-gated ion channels. Give an example of each.

Intracellular - Local anaesthetics, Anti-epileptics (Phenytoin).
Extracellular - Tetrodotoxin
Transmembrane- Scorpion Toxin.

12

In what state do local anaesthetics cross membranes?

As active, non ionised lipid soluble molecules.

13

Na+ channel blocking drugs reduce excitation. Give three examples.

Cocaine - Early Local Anaesthetic.
Lignocain- Dental local anaesthetic.
Tetrodotoxin - Puffer fish neurotoxin.

14

Drugs that modify the gating of Na+ channels cause excitation, but may then block nerve conduction. Give two examples.

Batrachotoxin- Dart frog neurotoxin.
Veratridine - Plant neurotoxin.

15

What are the effects of K+ channe blocking drugs such as tetramethylammonium.

Enhance excitation, prolonging action potentials. Used as anti-arrythmia agents and vasodilators.

16

What is the function of drugs that modify K+ ion channels, such as Cromakalim.

Reduce excitation of neurons, useful for peripheral vasodilators.