Voltage gated ion channels Flashcards
Ligand gated channels in the soma contribute how to the signal propagation?
Activation of voltage sensitive channels
How many alpha subunits does the voltage-gated sodium channel have?
4 repeats
How many times does the voltage-gated sodium channel pass through the membrane?
4
Where is the inactivation gate located?
Between repeats III and IV
What types of voltage-gated sodium channels are located in the CNS?
Nav1.1
Nav1.2
Nav1.3
How long is the transition of a voltage-gated sodium channel from activated to inactivated?
1ms
What is the Pk:PNa ratio for voltage-gated Na+ channels?
0.08:1
~1 K+: 10Na+
What factors is inactivation dependent on?
Time & voltage
What causes Nav inactivation?
Hinged lid or ball and chain in cytosol
What’s the typical amount of time necessary for deinactivation of Nav?
20ms
Where is the hinged lid located?
Between repeats 3 & 4
What amino acids form the hinged lid?
Isleucine
Phenylalanine
Methionine
All Na channels inactivate in what amount of time?
less than 5 ms
What local anesthetics are most commonly used, and how do they work?
LIdocaine and bupivacaine blocks voltage-gated ion channels
How does TTX induce death?
BLocks Na+ channel
How much TTX is needed to induce death?
1 micromol
HYPP is due to a defect in what type of channels?
Nav1.4
Describe the pathway of HYPP
Increase in ECF causes small membrane depolarization
Opens Na+ channels
Fault Na+ channels do not inactivate
Efflux of intracellular K+
How many alpha subunits make a Kv channel?
4
What are the common K+ channel motifs?
Kv1.1
Kv1.2
Kv2.1
Kv2.2
Can K channels ave mixed motifs?
Yes but only 1s with 1s & 2s with 2s
Which K+ channels are Ca2+ sensitive?
Kv2.1
Kv2.2
Which K+ channels are targets for many pharmaceuticals?
erg - Kv11
Does the K+ channel use the hinged lid or the ball and chain motif for inactivation? Where is it located?
Ball and chain
4-5 loop
Which transmembrane segment of the K+ channel is the voltage sensor?
TM4
What is the Pk:PNa ratio for K+channels?
10
When do K+ channels activate?
At peak of action potential
What subunit of Kv is necessar for de-inactivation?
Beta
Nav channels use the hinged lid and Kv channels use the ball and chain inactivation method. Which method is more rapid?
Hinged lid (Nav)
What happens if K+ channels are blocked?
Cell depolarizes
How long does activation of K+ channels take?
1s
What channels are responsible for the slight depolarization prior to an action potential?
Ligand-gated channels
What channels are responsible for the action potential?
VOltage-gated channels
What channels are responsible for the hyperpolarization after an action potential?
Voltage-gated channels
Which channels have the biggest impact on cardiac cells but little impact on other cells?
Calcium channels
What is the intracellular reglation of calcium channels?
Kinases & G-proteins
Which transmembrane segment is responsible for inactivation timer of calcium channels?
TM6 repeat I
What are the subunits of the calcium channel?
Apha, beta, gamma, delta
Which calcium channel is important for cardiac muscle?
Cav1 (L-type)
Which calcium channel targets the dorsal root ganglion?
Cav2 (P/N/R type)
During Ca2+ influx, does Ca2+ diffuse far through the cell? Why is this important?
No
Because there can be different Ca2+ concentrations at different parts of a cell
