Voltage gated ion channels

Question 1

Ligand gated channels in the soma contribute how to the signal propagation?

Answer 1

Activation of voltage sensitive channels

Question 2

How many alpha subunits does the voltage-gated sodium channel have?

Answer 2

4 repeats

Question 3

How many times does the voltage-gated sodium channel pass through the membrane?

Answer 3

4

Question 4

Where is the inactivation gate located?

Answer 4

Between repeats III and IV

Question 5

What types of voltage-gated sodium channels are located in the CNS?

Answer 5

Nav1.1
Nav1.2
Nav1.3

Question 6

How long is the transition of a voltage-gated sodium channel from activated to inactivated?

Answer 6

1ms

Question 7

What is the Pk:PNa ratio for voltage-gated Na+ channels?

Answer 7

0.08:1

~1 K+: 10Na+

Question 8

What factors is inactivation dependent on?

Answer 8

Time & voltage

Question 9

What causes Nav inactivation?

Answer 9

Hinged lid or ball and chain in cytosol

Question 10

What’s the typical amount of time necessary for deinactivation of Nav?

Answer 10

20ms

Question 11

Where is the hinged lid located?

Answer 11

Between repeats 3 & 4

Question 12

What amino acids form the hinged lid?

Answer 12

Isleucine
Phenylalanine
Methionine

Question 13

All Na channels inactivate in what amount of time?

Answer 13

less than 5 ms

Question 14

What local anesthetics are most commonly used, and how do they work?

Answer 14

LIdocaine and bupivacaine blocks voltage-gated ion channels

Question 15

How does TTX induce death?

Answer 15

BLocks Na+ channel

Question 16

How much TTX is needed to induce death?

Answer 16

1 micromol

Question 17

HYPP is due to a defect in what type of channels?

Answer 17

Nav1.4

Question 18

Describe the pathway of HYPP

Answer 18

Increase in ECF causes small membrane depolarization
Opens Na+ channels
Fault Na+ channels do not inactivate
Efflux of intracellular K+

Question 19

How many alpha subunits make a Kv channel?

Answer 19

4

Question 20

What are the common K+ channel motifs?

Answer 20

Kv1.1
Kv1.2
Kv2.1
Kv2.2

Question 21

Can K channels ave mixed motifs?

Answer 21

Yes but only 1s with 1s & 2s with 2s

Question 22

Which K+ channels are Ca2+ sensitive?

Answer 22

Kv2.1

Kv2.2

Question 23

Which K+ channels are targets for many pharmaceuticals?

Answer 23

erg - Kv11

Question 24

Does the K+ channel use the hinged lid or the ball and chain motif for inactivation? Where is it located?

Answer 24

Ball and chain

4-5 loop

Question 25

Which transmembrane segment of the K+ channel is the voltage sensor?

Answer 25

TM4

Question 26

What is the Pk:PNa ratio for K+channels?

Answer 26

10

Question 27

When do K+ channels activate?

Answer 27

At peak of action potential

Question 28

What subunit of Kv is necessar for de-inactivation?

Answer 28

Beta

Question 29

Nav channels use the hinged lid and Kv channels use the ball and chain inactivation method. Which method is more rapid?

Answer 29

Hinged lid (Nav)

Question 30

What happens if K+ channels are blocked?

Answer 30

Cell depolarizes

Question 31

How long does activation of K+ channels take?

Answer 31

1s

Question 32

What channels are responsible for the slight depolarization prior to an action potential?

Answer 32

Ligand-gated channels

Question 33

What channels are responsible for the action potential?

Answer 33

VOltage-gated channels

Question 34

What channels are responsible for the hyperpolarization after an action potential?

Answer 34

Voltage-gated channels

Question 35

Which channels have the biggest impact on cardiac cells but little impact on other cells?

Answer 35

Calcium channels

Question 36

What is the intracellular reglation of calcium channels?

Answer 36

Kinases & G-proteins

Question 37

Which transmembrane segment is responsible for inactivation timer of calcium channels?

Answer 37

TM6 repeat I

Question 38

What are the subunits of the calcium channel?

Answer 38

Apha, beta, gamma, delta

Question 39

Which calcium channel is important for cardiac muscle?

Answer 39

Cav1 (L-type)

Question 40

Which calcium channel targets the dorsal root ganglion?

Answer 40

Cav2 (P/N/R type)

Question 41

During Ca2+ influx, does Ca2+ diffuse far through the cell? Why is this important?

Answer 41

No | Because there can be different Ca2+ concentrations at different parts of a cell