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Neuroscience 3800 > Chapter 3 - Resting Membrane Potential > Flashcards

Chapter 3 - Resting Membrane Potential Flashcards

1
Q

intracellular environment has a negative electrical charge compared to the extracellular environment

A

cell is at rest

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2
Q

water

A
  • key ingredient in intracellular and extracellular environment
  • uneven charge
  • polar
  • covalent bonds
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3
Q

atoms or molecules with a net electrical charge

A

ions

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4
Q

held together by ionic bonds (electrical attraction of oppositely charged ions)

A

NaCl

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5
Q

dissolve in water due to uneven electrical charge (salt)
water loving
polarity of water molecule and an uneven (polar) electrical charge

A

hydrophilic

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6
Q

does not dissolve in water due to even electrical charge

  • non polar covalent molecules
  • shared electrons are distributed evenly (no net charge)
A

hydrophobic

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7
Q

Polar phosphate head group

A

PO4 atom and 3 oxygen atoms attached at one end

- hydrophilic

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8
Q

Building the Prototypical Neuron

A

1) lipid bilayer
2) membrane spanning channel proteins inserted into the lipid bilayer
3) receptor proteins

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9
Q

small subunit binds the

A

mRNA

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10
Q

large subunit bidns the

A

tRNA

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11
Q

all amino acids

A
  • central carbon atom (alpha carbon) covalently bonded to 4 molecular groups:
    1) hydrogren atom
    2) amino group
    3) carboxyl group
    4) residue group (varient)
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12
Q

join the amino group of one amino acid to the carboxyl group of another

A

peptide bond

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13
Q

chain of amino acids

A

polypeptide

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14
Q

primary structure

A

sequence

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15
Q

secondary structure

A

a-helix

spiral-like

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16
Q

tertiary structure

A

interactions with R-groups

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17
Q

Quaternary structure

A

over all structure
multiple peptide subunits
aggregate of subunits via weak molecular
bonds

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18
Q

polar r groups will ____ lipid environment

A

avoid (hydrophilic)

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19
Q

non polar r groups will ____ with lipids

A

associate (hydrophobic)

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20
Q

embedded (suspended) proteins

A

if proteins are arranged so that middle groups are non-polar and ends are polar.

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21
Q

channel proteins

A 
4-6 subunits
ion selectivity 
- size of pore 
- r group lining 
- k+, Na+, Ca 2+, Cl-
gating: closed or open
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22
Q

Na+ ions are ____ than K+ ions

A

smaller

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23
Q

site channel that weakly binds to Na + ions

A

Na + selectivity filter

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24
Q

Berti Hille et al (1984)

A
  • positive charge of ion is stabilized at a negative AA residue
  • H2O molecule is attracted to a second amino acid residue on the other side of the channel
  • K+ ion would be too large to bind effectively and would therefore be excluded.
25
Q

The movement of ions: passive processes

A

1) diffusion

2) electrostatic processes

26
Q

Diffusion

A

Dissolved ions distribute evenly
Ions flow down a concentration gradient
channels permeable to specific ions
concentration gradient across the membrane

27
Q

opposite charges attract

like charges repel

A

electrical (electrostatic) processes

28
Q

movements of ions: electricity

A

I: current

g: conductance
r: resistance
v: electrical potential

29
Q

movement of electrical charge

measured in amps

A

current (I)

30
Q

relative ability for the charge to migrate

measured in siemens (S)

A

conductance (g)

31
Q

inability of the charge to migrate

measured in Ohms

A

Resistance (R)

32
Q

difference in charge between anode and cathode

measured in volts (V)

A

electrical potential (V)

33
Q

electrical current flow across a membrane

A

electricity

34
Q

deals with the relationship between voltage and current in an ideal conductor. This relationship states that:

The potential difference (voltage) across an ideal conductor is proportional to the current through it.

A

Ohm’s law

The constant of proportionality is called the “resistance”, R.

Ohm’s Law is given by:

V = I R

where V is the potential difference between two points which include a resistance R. I is the current flowing through the resistance. For biological work, it is often preferable to use the conductance, g = 1/R; In this form Ohm’s Law is:

I = g V
35
Q

Ohm’s law

A

The constant of proportionality is the “resistance”, R.
conductance, g = 1/R
I = g V

36
Q

voltage potential across the neuronal membrane

A

membrane potential

37
Q

at rest (RMP)

A

-65 - -70 mV

38
Q 
concentrations of ions at rest inside the cell 
Na+ 
K+ 
Cl-
Ca2+
Protein
A 
Na+ few
K+ lots
Cl- fewer
Ca2+ fewer 
Protein many
39
Q 
concentrations of ions at rest outside the cell 
Na+ 
K+ 
Cl-
Ca2+
Protein
A 
Na+ lots 
K+ few
Cl- more 
Ca2+ more 
Protein few
40
Q

without channels

A

no movement of ions when separated by a phospholipid bilayer

41
Q

Water chemically combined with a substance in such a way that it can be removed, as by heating, without substantially changing the chemical composition of the substance.

A

waters of hydration

42
Q

K+channels inserted: > K+inside (large concentration gradient =diffusion)
A - are left behind: cell would have net negative charge

A

Equilibrium potential (K+)

43
Q 
there is a point when the inside of the cell is so negative it will start to draw the pos charged molecles back into the cell
electrical fore (+/-) counterbalances the force of diffusion pushing K+ out (no net movement)
A 
Equilibrium potential (K+) 
= -80mV
44
Q

greater [Na+] outside
Na+ channels inserted:
- Na+ flows down conc gradient into the cell
- electrical forces also drive cell from pos environment to neg environment
- cell is more positive
reach a point when the charge is also positive it inhibits movement of Na+

A

Equilibrium potential for Na+

= +55 mV

45
Q

calculates the exact value of an equilibrium potential in mV

  • takes into consideration:
  • charge of ion
  • temperature
  • ratio of the external and internal ion concentrations
A

Nernst Equation

E(ion)=2.303 RT/ZF logs ([ion]o/[ion]i)

E(ion) = equilibrium potential
RT = gas constant 
Z = ion charge 
F = faraday's constant 
[ion]o = external ion concentration 
[ion]i=internal ion concentration
46
Q

the distribution of ions across the membrane

A

K+: 80 mV
Na+: 62 mV
Ca2+ : 123 mV
Cl-: -65 mV

47
Q

the membrane is more permeable to Na+ or K+?

A

K+

48
Q

Takes into account permeability of membrane to different ions

P=Permeability
[ion] concentration inside or outside
Constants R and F (Nernst)
T= temperature (Kelvin)
Log function
A

Goldman equation

49
Q

shape changing

A

allosteric

50
Q

how many subunits are in a K+ channel

A

4 subunits

51
Q

channel selectively permeable to K+ ions

A

pore loop

52
Q

The importance of regulating the external potassium concentration

A

Increasing extracellular K+ will lead to a depolarization of the membrane.

53
Q

what does the blood brain barrier do to the flow of K+

A

blood brain barrier limits the flow of K+

54
Q

K+ pumps that take up K+

A

potassium spatial buffering (astrocytes)

55
Q

differences between channels and pumps/transporters:

A

1.Channels are passive conduits, pumps transport ions against the electrochemical gradient (expending energy)

2.Ion transport is much faster in channels
Channels: 10^7– 10^8
ions/second
Transporters: 10,000 times slower

56
Q

The sodium-potassium pump

transporter

A

Enzyme - breaks down ATP when Na+ present
1 molecule of ATP/hydrolyzed/cycle Na+/K+- ATPase
ATP-ligand

57
Q

The calcium-pump (and more)

A

Calcium concentrated outside of the cells
Calcium pump: Actively transports Ca2+ out of cytosol

Calcium is a very important intracellular signal:
Mitochondria
ER
NT release

58
Q

Conclusions: Neuron at Rest

A

Activity of the sodium-potassium pump

Movement of K+
ions across membrane
Electrical potential difference across the membrane
Similar to a battery
Potassium channels
Contribute to resting potential
Roles of ion pumps

Neuroscience 3800 (5 decks)

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