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Cell and Molecular Neuroscience > West Material > Flashcards

West Material Flashcards

1
Q

Phospholipid bilayer acts as what in circuit of cell?

A

Capacitor.
Cap. is proportional to Area.
Cap is inversely proportional to distance

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2
Q

At what rate do ion channels conduct ions across the plasma membrane?

A

“at a rate near the diffusion limit across the plasma membrane

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3
Q

Do ions move faster through ion channels or carriers?

A
  • ion channels
  • (10^6-10^8 ions/sec)
  • current equivalent (10^-12-10^-10 amps (1-100 pA))

Na-K exchanger
* 300 Na+, 200 k+ /sec
* Current equivalent of 1.5x10^-17 A.

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4
Q

Define Nernst Potential

A

-Calculated potential at which the concentration of an ion inside and outside a cell is in equilibrium.
-Driving force due to charge separation is exactly equal and opposite to chemical force due to concentration gradient.
-Potential at which the net current of an ion is zero.

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5
Q

Nernst Potential Equation

A

E_x = RT/zF * ln([x]_out / [x]_in)
F = Faradays Constant (F = 96485.3321233100184 C mol−1)
R = gas constant (R = 8.31446261815324 J K−1 mol−1,)
z = Valence
T = Temperature (in Kelvin)

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6
Q

Nernst Table

A
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7
Q

Sodium Concentrations outside and inside cell

A

[Na+]_out = 145
[Na+]_in = 18

Results in a Nernst Potential of +56

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8
Q

Potassium Concentrations without and within cell

A

[K+]_out = 3
[K+]_in = 135

Results in a Nernst Potential of -102

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9
Q

Chlorine Concentrations within and without a cell

A

[Cl-]_out = 120
[Cl-]_in = 7

Results in a Nernst Potential of -76

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10
Q

Calcium Concentrations within and without a cell

A

[Ca2+]_out = 1.2
[Ca2+]_in = .1uM

Results in a Nernst Potential of +125

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11
Q

Na-K Pump

A

pumps 3 Na+ out of cell, pumps 2 K+ into cell

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12
Q

Goldman-Hodgkin-Katz Voltage Equation

A

notice Cl is inverted because of it’s valence

58*log is replacing RT/F ln()

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13
Q

Choroid Plexus

A
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14
Q

Ion Channels as resistors

A
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15
Q

Full Neuronal Circuit

A
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16
Q

Time Constant Equation

A

Tau = RmCm
Rm = membrane Resistance
Cm = membrane Capictance

REMEMBER: SMALLER == FASTER

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17
Q

Length Constant

A

Lambda = sqrt(Rm/Ra)
Rm = membrane Resitance
Ra (Ri) = axial Resistance

REMEMBER: LARGER == LESS DEGRADATION

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18
Q

Action Potential related changes in conductances

A

Sequential increases in Na+ and K+ conductances

19
Q

Current Equation for specific ion

A

I_x = g_x * (V_m - E_x)
E_x = equilibrium potential. This is empirically determied by reversal potential

20
Q

How to Draw IV Curves

A

Current = 0 @ Ex. Draw a straight dotted line with an x-intercept @ Ex. Channel is closed prior to it opening, when it’s opening voltage is reached, it slowly approaches the dotted line. When channel fully open, it joins the line and follows it.

21
Q

Positive Current flows in which directions

A

FOR DR. WEST (voltage clamping): positive current is out of the cell. Negative current is cations flowing into the cell

22
Q

Structural Components of Voltage Gated Ion Channels

A
  1. Transmembrane, extra- & intra-cellular domains
  2. Gates
  3. Pore and Selectivity Filter
  4. Voltage Sensor
23
Q

How many domains in alpha subunits of Voltage-gated sodium channel have? How many transmembrane segments does each domain have?

A

4 homologous domains.
6 transmembrane segments

24
Q

Which alpha subunit is the primary voltage sensor for Sodium gated channel?

A

S4

contains multiple charged amino acids

25
Q

Which alpha subunit is the primary voltage sensor for Sodium gated channel?

A

S4

contains multiple charged amino acids (R,K)

26
Q

Which subunit contains the inactivation gate?

A

Also S4

27
Q

Why can’t sodium fit through potassium selectivity filter?

A

K+ ions are dehydrated as they pass through their channel’s selectivity filter

28
Q

Cardiac AP

A
29
Q

Cardiac AP ion channels

A
30
Q

What makes the inward Rectifier K+ channel unique

A

Only 2 alpha-helices

Kir2.x constitutively active

31
Q

Difference between strong/weak rectifiers?

A

Strong rectifiers’ activity silenced at higher voltages

32
Q

Role of inward rectifier K channels

A

maintain ionic and osmotic enviornment in extracellular space

33
Q

Updated mathmatical model of cells with voltage gates

A
34
Q

Hodgkin Huxley Current Equation

A
35
Q

2D alpha subunit

A
36
Q

HERG

A

Human ether a go-go related gene. It’s a cardiac potassium current

results in long QT syndrome

I think this question will turn into a K2.2 channel question.

37
Q

What effect does myelin have on electrical transmission?

A

decreases time constant
increases length constant
increases membrane resistance and decreases membrane capacitance

38
Q

In mylinated axons, where are voltage gated channels?

A

they cluster at Nodes of Ranvier

39
Q

How is mylinated transmission discussed?

A

Saltatory Conduction: from the Latin Saltare, which means to leap

40
Q

How many AA in Na channel alpha domain?

A

2000

41
Q

Kv7.1 (KCNQ1)

A

Short QT syndrome
(like inward rectifier)

42
Q

Kv7.2 (KCNQ2)

A

BFNC

43
Q

Kv7.3 (KCNQ3)

A

BFNC

Cell and Molecular Neuroscience (15 decks)

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