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Intracardiac neuron electrophysiology > Voltage gated channels > Flashcards

Voltage gated channels Flashcards

1
Q

How to isolate sodium channels

A

Replace intracellular potassium with caesium and add cadmium And tea to external

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2
Q

Sodium conductance characteristics

A

Activation Threshold -40 mV
Sigmoidal increase with voltage
Half Max -25 mV

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3
Q

Potentially what explains stimulus dependent decrease of nerve evoked EPSP?

A

Slow recovery from sodium channel inactivation

Time constant 20 ms accelerated with membrane hyper polarisation

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4
Q

What does ciguatoxin do to neuronal excitability?

A

Increases neuronal excitability and causes spontaneous opening of single sodium channels by shifting voltage of activation to more negative potentials

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5
Q

How do you isolate calcium channels?

A

Inhibit sodium currents with TTX or replace external sodium with an impermeable cation, and suppress potassium currents with intracellular caesium and/or extracellular TEA

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6
Q

The affect of barium on calcium channels

A

1.5 fold increase in current density

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7
Q

Calcium conductance characteristics

A

Activation threshold -30 MV, sigmoidal increase with depolarisation, Half max -5 MV

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8
Q

Effect of barium on calcium activation curve

A

Shifted 10 mV to more negative potentials

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9
Q

Which sodium channels are present?

A

TTX sensitive Nav1.1-1.3,1.7

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10
Q

Which types of calcium channels are present?

A

L, N, P/Q and R

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11
Q

What’s the L type molecular identity and antagonist?

A

Cav1.2 and Dihydropyridines (eg nifedipine)

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12
Q

What is the N type molecular identity and antagonist?

A

Cav2.1 and omega conotoxin gvia

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13
Q

What is the PQ identity and antagonist?

A

Cav2.2 and omega conotoxin mviic

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14
Q

What is R type identity and antagonist?

A

Cav2.3 and nickel ions

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15
Q

What potassium channels are present?

A

Kv, A, BKCa, AHP, Kir, Katp, M

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16
Q

What is the Kv type identity and antagonist?

A

Kv1.5,1.6, and TEA, verapamil

17
Q

What is that IA type identity and antagonist?

A

kv3.x, kv4.x, 4 aminopyridine

18
Q

What is the AHP antagonist?

A

Ryanodine

19
Q

What is the KiR identity and antagonist?

A

Kir2.x, Kir3.x, Barium

20
Q

What is the KATP identity and antagonist?

A

Kir6.x/Sur1-2, glibenclamide

21
Q

What is the M type identity and antagonist?

A

KCNQ1-5, XE991 (linopirdine)

22
Q

What is the H type identity and antagonist?

A

HCN1-4, caesium etc

23
Q

Main calcium channel which is target different neuro transmitters?

A

N type

24
Q

What is IKv called and what is its function?

A

Delayed outward rectifier, terminate action potential rapidly.

25
Q

Delayed outward rectifier conductance characteristics

A

Activation threshold -40 mV, increase with voltage until saturation about 20 mV

26
Q

What is the Potassium current IA called and what is its function?

A

Transient outward current, activated in sub threshold range of neuronal excitation and functions to reduce the excitatory effects of depolarising stimuli by decreasing rate of decay of AHP

27
Q

What are the effects of 4-AP?

A

Inhibits transient outward current IA responsible for AHP decay, increase firing frequency

28
Q

What is iKca and what is it function?

A

Calcium dependent potassium current , Hyperpolarise cell after burst of action potentials sufficient to raise intra cellular Calcium

29
Q

What is Ikir and what is its function?

A

Inward rectifying current, hyperpolarisation activated. Outward current blocked by intracellular magnesium. Maintain resting membrane potential

30
Q

What is iKca and what is it function?

A

Calcium dependent potassium current , Hyperpolarise cell after burst of action potentials sufficient to raise intra cellular Calcium

31
Q

What is IkATP and what is it function?

A

ATP sensitive potassium current, transduce changes in cell metabolism to membrane potential. Open at low ATP concentration.

32
Q

What is IM and what is it function?

A

Muscarine sensitive, noninactivating potassium current. Partially activated at rest. ACh evokes slow depolarisation associated with increased membrane resistance and decreased outward current resulting from inhibition of IM.

Intracardiac neuron electrophysiology (2 decks)

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