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Neurobiology I > Electrical Signals in Neurons > Flashcards

Electrical Signals in Neurons Flashcards

1
Q

Voltage

A

Difference in electrical potential between 2 points

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2
Q

Voltage requires 2 _____ separated by a _____, such as a ____ in a neuron.

A

Compartments
Barrier
Membrane

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3
Q

Voltage will occur only if there are ____ ____ on at least 1 side of the barrier.

A

Charged molecules

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4
Q

If there is an equal charge on both sides, the net charge will be ____.

A

0

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5
Q

Permeability

A

Ability of molecules to move from one side to another

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6
Q

In the absence of permeability, is it possible to have voltage?

A

Yes

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7
Q

Current

A

Flow of electrical charge from one side to another

Net movement of ion

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8
Q

Is permeability required for current? If so, how many ions?

A

Yes

One or more

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9
Q

If the barrier is equally permeable to all ions, there will be current until when?

A

Ion concentrations and/or charge are equal on both sides of barrier

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10
Q

Molecules move along a chemical gradient from ___ to ___ concentration.

A

High

Low

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11
Q

Charged molecules move toward the ___ charge.

A

Opposite

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12
Q

Electrical gradient

A

Difference in total charge between one side and the other

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13
Q

Driving force is also called what?

A

Electrochemical gradient

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14
Q

How is driving force calculated?

A

DF= CG (chemical gradient) + EG (electrical gradient)

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15
Q

Conductance

A

How well an ion can pass through a membrane

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16
Q

What does driving force measure?

A

How much an ion wants to pass through the membrane

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17
Q

How is current calculated?

A

I (current) = DF x g (conductance)

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18
Q

What are 2 conditions in which current is 0?

A

g=0: no permeability

DF=0: ion doesn’t want to move

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19
Q

Is direction of chemical gradient determined as a sum or individually for each ion?

A

Individually for each ion

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20
Q

Is electrical gradient determined as a sum or individually for each ion? Direction an ion moves?

A

Electrical gradient is determined by sum of all charges on each side of the barrier
Direction ion moves depends on its charge relative to the electrical gradient

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21
Q

In most neurons, which is more negative, the outside or the inside? Difference in charge between inside and outside means that the neuron is ___.

A

Inside is more negative than the outside

Neuron is polarized

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22
Q

Membrane potential (Vm)

A

Charge inside vs outside

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23
Q

Resting membrane potential is recorded when?

A

When neuron is not firing

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24
Q

Most neurons have a resting membrane potential of ___ to ___ mV.

A

-40 to -80 mV

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25
Q

A stimulus causes the ____ _____ of the neuron to open. What is happening to the membrane?

A

Ion channels

Membrane becomes permeable/conductive to ion

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26
Q

Flow of ions in neuronal response causes change in ___ ___.

A

Membrane potential (Vm)

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27
Q

How much current will flow during a neuronal response depends on what 3 factors?

A

Concentration gradient of ion
Voltage across membrane
Whether or not membrane is permeable

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28
Q

Can you have voltage without current? Current without voltage?

A

Yes

No

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29
Q

Receptor potential: when is it created, how much depolarization?

A

Activation of sensory receptor neuron

Causes a small amount of depolarization

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30
Q

Synaptic potential: when is it created, how much depolarization

A

Single neuron synapses

Causes a medium amount of depolarization

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31
Q

Action potential: when is it created, how much depolarization?

A

Signal sent down axon to another neuron

Causes the biggest amount of depolarization

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32
Q

When potential is measured on a graph, what is the x axis measuring? Y axis?

A

X axis: time in ms

Y axis: membrane potential in mV

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33
Q

Equilibrium potential

A

Membrane potential at which there is no net movement of the ion

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34
Q

Ions move only if there is ____ ____.

A

Driving force

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35
Q

If concentration gradient is equal and opposite to electrical gradient, then DF=__ and there will be no ___ ___ of ___, even if there is ____.

A

0
Net movement of ions
Permeability

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36
Q

Equilibrium potential of an ion occurs at a ____ or ___ ___ at which concentration gradient and electrical gradient for the ion are ____ and _____.

A

Voltage or membrane potential

Equal and opposite

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37
Q

How can driving force be calculated using membrane potential and equilibrium potential?

A

DF= Vm (membrane potential) - Ex (equilibrium potential)

38
Q

If an ion is at equilibrium, what is the value for its current? Why?

A

0 (ions are no longer moving)

39
Q

If an ion is at equilibrium, what is its driving force? Why?

A

0 (concentration gradient and electrical gradient are equal and opposite, so ion doesn’t want to move)

40
Q

When ions move, the direction and magnitude of the current are always determined by what 2 factors?

A

Driving force

Conductance/permeability

41
Q

How can current be calculated from conductance, membrane potential, and equilibrium potential?

A

I = g x DF

Since DF = Vm-Ex, I = g x (Vm-Ex)

42
Q

To get current, the barrier must be ____ ____. Why is this?

A

Selectively permeable

If the barrier is completely permeable, the situation goes to equilibrium

43
Q

At equilibrium, is there current? Is the potential stable or fluctuating?

A

No net current

Potential remains stable (at rest)

44
Q

In a situation where an ion can pass through a barrier permeable to it, when does it stop moving?

A

When its electrical gradient is equal and opposite to its concentration gradient

45
Q

The Nernst equation calculates what?

A

Ion equilibrium potential

46
Q

What is the formula for the Nernst equation?

A 
Ex= [(RT)/(zF)]*log([X0]/[Xi])
Ex= equilibrium potential in mV
R= gas constant
T= absolute temperature in K
F= Faraday constant
z= valence of ion, including sign
[X0]= concentration of ion X outside
[Xi]= concentration of ion X inside
47
Q

RT/F in the Nernst equation equals what?

A

58 mV

48
Q

At what temperature is RT/F in the Nernst equation measured?

A

19 degrees C

49
Q

LogX = Y can be written what other way?

A

10^Y = X

50
Q

At an equilibrium potential of 0, what is the magnitude of inside vs outside concentration relative to each other?

A

Inside and outside concentration are the same

51
Q

At equal concentrations of an ion, what is the membrane potential for that ion?

A

0

52
Q

The membrane potential is basically equal to the ___ ___.

A

Electrical gradient

53
Q

The membrane potential at which equilibrium is reached is the same as the ___ ___.

A

Equilibrium potential

54
Q

What does the “ten fold” rule for the Nernst equation state?

A

At 19 degrees C, every 10 fold change in ion concentration causes a change in equilibrium potential of 58/z

55
Q

For a positively charged ion, increasing the ratio of outside to inside ion concentration does what to the equilibrium potential? Decreasing the ratio of outside to inside ion concentration?

A

Increases equilibrium potential

Decreases equilibrium potential

56
Q

Does the “ten fold” rule apply to membrane potential?

A

No- applies only to equilibrium potential in Nernst equation

57
Q

When a battery is inserted into a situation with ions and a selectively permeable barrier, how will its voltage affect the movement of the ions?

A

The voltage from the battery will drive the ions to move to the appropriate concentration gradient that is equal and opposite the imposed electrical gradient

58
Q

For a positively charged ion, movement from outside the cell to inside the cell is called what?

A

Inward current

59
Q

For a positively charged ion, movement from inside the cell to outside the cell is called what?

A

Outward current

60
Q

An inward current will always ____ the membrane potential and an outward current will always ____ the membrane potential.

A

Increase

Decrease

61
Q

The ion always moves to bring ____ potential toward ___ potential.

A

Membrane

Equilibrium

62
Q

The equilibrium potential for an ion is also called the ____ ____ for the ion. Why?

A

Reversal potential

The direction of the ion’s current switches at the equilibrium potential

63
Q

Assuming permeability, what will happen to membrane potential as ion concentration changes?

A

Membrane potential will change

64
Q

As membrane potential changes, what will happen to ions?

A

Driving force on ions will change

If permeability is present, current will change

65
Q

When the equilibrium potential equals the membrane potential, what is the magnitude of driving force and current?

A

Both driving force and current are 0

66
Q

When equilibrium potential is greater than membrane potential, what kind of current results?

A

Inward current (ion moves to increase membrane potential)

67
Q

When equilibrium potential is less than membrane potential, what kind of current results?

A

Outward current (ion moves to decrease membrane potential)

68
Q

For a negative ion, inward current means moving from ___ to ___ the cell.

A

Inside to outside (bringing membrane potential up)

69
Q

For a negative ion, outward current means moving from ___ to ___ the cell.

A

Outside to inside (bringing membrane potential down)

70
Q

In biology, will plotting current vs membrane potential give you a linear graph? Why or why not?

A

No- linear graph assumes constant permeability, and permeability is determined by channels, which are gated and voltage-dependent, so they are not always open

71
Q

In a single neuron with a voltage-gated ion channel, conductance can be approximated as __ when the channel is closed and ___ when the channel is open.

A

0

1

72
Q

In a biological system, conductance of a value between 0 and 1 comes from what?

A

Multiple voltage-gated ion channels: some are open and some are closed

73
Q

Plotting driving force on a graph will give you what kind of plot?

A

Linear

74
Q

For a driving force of 1 and a driving force of -1, they both have the same ____ but different ____.

A

Magnitude

Directions

75
Q

What are the 4 abundant ions in mammalian neurons for which channels exist?

A

Na+
K+
Ca+2
Cl-

76
Q

Which of the 4 ions typically has a larger concentration inside the neuron than outside?

A

K+

77
Q

Which ion doesn’t contribute much to the overall membrane potential, but has a large driving force due to its large concentration gradient?

A

Ca+2

78
Q

At rest, the neuronal membrane is primarily permeable to what ion due to what channels?

A

K+

K+ leak channels

79
Q

The resting membrane potential of the neuron is closest to the equilibrium potential of what ion? Why? What is that value?

A

K+
Because the membrane is primarily permeable to K+
Approximately -60 mV

80
Q

Goldman equation

A 
Vm = (RT)/F * log (PK [K0] + PNa [Na0] + PCl [Cli])/(PK [Ki] + PNa [Nai] + PCl [Cl0])
Vm = membrane potential
RT/F = 58 mV
P= permeability for an ion
81
Q

In the Goldman equation, why is inside concentration of Cl over outside concentration of Cl?

A

There is no sign for valence, so o/i for negative ions like Cl are flipped

82
Q

In the Goldman equation, which ion will have the highest permeability at rest?

A

K+

83
Q

In the Goldman equation, the greater the permeability, the ___ the effect an ion will have on membrane potential

A

Greater

84
Q

The Nernst equation predicts how ___ potential changes with ion concentration

A

Equilibrium

85
Q

Driving force makes ions “want” to move until ____ equals ____.

A

Membrane potential

Equilibrium potential

86
Q

When estimating how an ion’s concentration will affect membrane potential, use the ____ equation.

A

Goldman

87
Q

Under normal biological conditions, will opening a specific ion’s channel move the membrane potential past its equilibrium potential? Why or why not?

A

No- ion moves to bring membrane potential toward equilibrium potential, so ion will reach equilibrium at equilibrium potential and won’t move past that voltage

88
Q

What is a main difference in how equilibrium potential and membrane potential are determined?

A

Equilibrium potential is determined for a single ion, but membrane potential is determined through the summation of ions

89
Q

The direction an ion moves depends on the relationship between what 2 factors?

A

Membrane potential and equilibrium potential

90
Q

In a cell, changing permeability is caused by what?

A

Opening or closing ion channels

Neurobiology I (18 decks)

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