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Neuroscience > Chapter 3 > Flashcards

Chapter 3 Flashcards

1
Q

What is membrane potential?

A

Membrane potential is the difference in electrical charges across the membrane

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2
Q

What is the membrane potential at rest?

A

At rest, the neuron has a steady negative electrical potential

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3
Q

What is electrical potential?

A

Electrical potential is the force exerted on a charged particle (ion)

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4
Q

Our typical neuron has a resting membrane potential of about…

A

-65 mV

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5
Q

The neuronal membrane separates…

A

Charge

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6
Q

How is the resting membrane potential established and maintained?

A
  1. Charge separation (neuronal membrane)
  2. Selective permeability (ion channel proteins)
  3. Concentration gradients (ion pumps: Na+/K+ ATPase)
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7
Q

Why is water important in the membrane?

A

Water’s the key ingredient in extracellular & intracellular fluid
- Water IS A POLAR SOLVENT

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8
Q

What are ions?

A

Ions are atoms or molecules with a net electrical charge
- Hydrophilic

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9
Q

What charge do cations have?

A

Net positive charge

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10
Q

What charge do anions have?

A

Net negative charge

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11
Q

What does the phospholipid bilayer consist of?

A

Lipids and phosphate groups

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12
Q

Lipids are hydro___

A

Hydrophobic

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13
Q

Phosphate groups are hydro___

A

Hydrophilic

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14
Q

Why can’t ions pass the lipid bilayer?

A

Ions in solution are hydrated and therefore cannot pass across the hydrophobic core of the cell membrane lipid bilayer

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15
Q

What are proteins?

A

Proteins are molecules assembled from amino acids (ex: enzymes, cytoskeletal elements, receptors, ion channels)

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16
Q

What are transmembrane proteins?

A

Transmembrane proteins are special proteins that span the phospholipid bilayer

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17
Q

What are the functions of transmembrane proteins?

A
  • Control resting membrane potential and action potentials
  • Control synaptic transmission
  • Control extracellular to intracellular signaling
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18
Q

Proteins are structured via…

A

Amino acids

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19
Q

What do amino acids consist of?

A

Amino acids are made of a alpha carbon and an R group
- Linked together via peptide bonds to form polypeptides

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20
Q

What 4 layers do proteins consist of?

A
  1. Primary
  2. Secondary
  3. Tertiary
  4. Quaternary
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21
Q

What does the primary protein layer consist of?

A

Sequence of amino acids in polypeptide

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22
Q

What does the secondary protein structure consist of?

A

Coiling of polypeptide into alpha helix

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23
Q

What does the tertiary protein structure consist of?

A

3-dimensional folding of the polypeptide

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24
Q

What does the quaternary protein structure consist of?

A

Different polypeptides bonding together

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25
Q

What are channel proteins?

A

Polar R groups (exposed to cytosol or extracellular fluid) and non-polar R groups (imbedded in the membrane)

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26
Q

What are channel proteins responsible for?

A

Ion selectivity and gating

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27
Q

What are the different types of ion channels?

A

Voltage gated, Ligand gated, “Leak”

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28
Q

What is the purpose of voltage gated ion channel?

A

Contribute to action potential

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29
Q

What is the purpose of ligand gated ion channel?

A

Contribute to alterations in post-synaptic potentials (PSP)

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30
Q

What is the purpose of “leak” ion channel?

A

Alter resting membrane potential (RMP)

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31
Q

What are the functions of ion pumps?

A
  • Critical for establishing cellular concentration gradients
  • Formed by membrane-spanning proteins
  • Use energy from ATP breakdown
    ex: sodium-potassium pumps, calcium pumps
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32
Q

What is the sodium-potassium pump?

A
  • An enzyme that breaks down ATP when Na is present
  • Pumps 3 Na+ ions out, 2 K+ ions in
  • Uses ~70% of the total amount of ATP in the brain
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33
Q

What is the concentration of Na+ in extracellular fluid?

A

150 mM

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34
Q

What is the concentration of K+ in extracellular fluid?

A

5 mM

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35
Q

What is the concentration of Na+ in cytosol?

A

15 mM

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36
Q

What is the concentration of K+ in cytosol?

A

100 mM

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37
Q

What is diffusion force?

A

The force on an ion due to its concentration gradient (ex: the ratio of extracellular to intracellular concentration of an ion)

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38
Q

What is electrostatic force?

A

The force on an ion produced by the membrane voltage
- the amount and direction of the force is a function of the membrane voltage and the charge ion

39
Q

What is equilibrium ptential?

A

A voltage (electrostatic force) that exactly offsets the diffusional force of the ion
- It is the point where diffusion and electrostatic forces counteract each other
- Calculated by the Nernst Equation

40
Q

What is driving force?

A

The sum of the diffusion and electrostatic forces
- The force that controls the rate of ion flux IF the membrane is permeable to the ion (the ion flux then alters the Vm)
- Calculated by Vm-Eion (membrane voltage minus ionic equilibrium potential)

41
Q

What is ion flux?

A

The mechanism by which membrane potential is changed
- Controlled by the driving force of an ion and the permeability f the membrane to that ion

42
Q

What is the Law of Permeability?

A

The membrane potential is always driven toward the equilibrium potential of the ion to which the membrane is most permeable

43
Q

How do ions move throughout a membrane?

A

Ions diffuse throughout a membrane
- Dissolved ions distribute evenly
- Ions flow down the concentration gradient when channels are permeable to specific ions and the concentration gradient exists across the membrane

44
Q

How does electrical potential correlate with ion movement?

A

Electrical potential (voltage) influences ion movement

45
Q

Electrical current (I) is directly proportional to…. and inversely proportional to….

A

Electrical potential (V), resistance (R)

46
Q

Ohm’s Law

A

I= V/R
V= IR
I: current (amperes)
V: voltage across the conductor (volts)
R: resistance of the conductor (ohms)

47
Q

How does electrical current move across a membrane?

A

Electrical current flows across a membrane

48
Q

What does it mean to be in “equilibrium potential”?

A
  • No net movement of ions when separated by a phospholipid membrane
  • Equilibrium reached with K+ channels in the phospholipid bilayer
  • Electrical potential different that exactly balances ionic concentration gradient
49
Q

What is the voltage that will exactly counteract the ion’s diffusional force (concentration gradient)?

A

Equilibrium potential (electrostatic force)

50
Q

What is membrane potential (Vm)?

A

The voltage across the neuronal membrane at any moment

51
Q

How do changes in membrane potential occur?

A

Large changes in membrane potential occur even with small changes in ionic concentrations

52
Q

Electrical charges are ___ at the inside and outside membrane surfaces

A

Balanced

53
Q

Rate of movement of ions across membrane (should it become permeable to that ion) is determined by…

A

Driving force

54
Q

If concentration difference is know, equilibrium potential can be calculated using….

A

Nernst Equation

55
Q

Potassium equilibrium potential is ___ relative to outside

A

Negative; -Vm

56
Q

Sodium equilibrium potential is ___ relative to outside

A

Positive; +Vm

57
Q

Increasing the concentration gradient or temp will ____ the absolute value of equilibrium potential

A

Increase

58
Q

An ion with twice the charge will have ____ the equilibrium potential

A

Half

59
Q

The Nernst Equation

A

Eion= 2.303 RT/zF log [ion]out//[ion]in
Eion= equilibrium potential
R= gas constant
T= absolute temperature
F= Faraday’s constant
z= charge of the ion (valence)

60
Q

K+ is more concentrated on ____

A

Inside

61
Q

Na+ and Ca2+ is more concentrated ____

A

Outside

62
Q

What is the concentration of K+ outside and inside the membrane?

A

Outside: 5; Inside: 100

63
Q

What is the ratio Out:In of membrane concentration for K+?

A

1:20

64
Q

What is Eion for K+?

A

-80 mV

65
Q

What is the concentration of Na+ outside and inside the membrane?

A

Outside: 150; Inside: 15

66
Q

What is the ratio Out:In of membrane concentration for Na+?

A

10:1

67
Q

What is Eion for Na+?

A

62 mV

68
Q

What is the concentration of Ca2+ outside and inside the membrane?

A

Outside: 2; Inside: 0.0002

69
Q

What is the ratio Out:In of membrane concentration for Ca2+?

A

10,000:1

70
Q

What is Eion for Ca2+?

A

123 mV

71
Q

What is the concentration of Cl- outside and inside the membrane?

A

Outside: 150; Inside: 13

72
Q

What is the ratio Out:In of membrane concentration for Cl-?

A

11.5:1

73
Q

What is Eion for Cl-?

A

-65 mV

74
Q

The membrane potential is always driven ____ the equilibrium potential to which the membrane is most ____

A

Toward; permeable

75
Q

What is the Nernst Equation for K+?

A

61.54mV x log [ion]out/[ion]in

76
Q

What is the Nernst Equation for Na+?

A

61.54mV x log [ion]out/[ion]in

77
Q

What is the Nernst Equation for Cl-?

A

-61.54mV x log [ion]ut/[ion]in

78
Q

What is he Nernst Equation for Ca2+?

A

30.77mV x log [ion]out/[ion]in

79
Q

The membrane potential is the ___ as an equilibrium potential for an ion if the membrane is ____

A

Same; permeable ONLY to that ion

80
Q

What does resting cell mean?

A

Resting cell means there is no special synaptic event or action potential

81
Q

In the resting cell, no ion is _____

A

Strictly impermeable across the membrane

82
Q

What is the order of permeability?

A

K+&raquo_space; Cl-&raquo_space;> Na+

83
Q

Is the K+ leak channel a ligand gated or voltage gated?

A

The K+ leak channel is neither ligand gated or voltage gated

84
Q

The default state of K+ leak channel is ____

A

Open

85
Q

Where does the K+ leak channel exist?

A

The K+ leak channel exists in all zones of the neuronal membrane (dendrites, soma, axon)

86
Q

The K+ leak channel results in ___ resting permeability to K+?

A

High

87
Q

Why is there a large outward diffusional force on K+?

A

There is a large diffusional force on K+ due to its concentration gradient?

88
Q

What is a key determinant of resting membrane potential?

A

Selective permeability of potassium channels

89
Q

Mutations of specific K+ channels lead to ___

A

Inherited neurological disorders

90
Q

Why is it important to regulate external K+ concentration?

A
  • Resting membrane potential is close to Ek because it is mostly permeably to K+
  • Membrane potential sensitive to extracellular K+
  • Increased extracellular K+ depolarizes membrane
91
Q

What mechanisms regulate the external potassium concentration?

A

Blood-brain barrier and potassium spatial buffering by astrocytes

92
Q

Membrane permeability determines…

A

Membrane potential

93
Q

What is the purpose of the Goldman equation?

A

It takes into account permeability of membrane to different ions

Neuroscience (8 decks)

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