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General Physiology > 5 Membrane Potential > Flashcards

5 Membrane Potential Flashcards

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1
Q

What is the function of neurons in the nervous system?

A

Neurons receive, process, and transmit information to other cells.

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2
Q

What are the three (3) main parts/functional units of a neuron?

A
  • Soma (metabolic maintenance)
  • dendrites (receive signals)
  • axons or nerve fibers (transmit signals)
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3
Q

A part/functional unit of a neuron that is responsible for the metabolic maintenance of the neuron.

A

Soma

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4
Q

What is the role of the soma in a neuron?

A

responsible for the metabolic maintenance of the neuron.

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5
Q

A part/functional unit of a neuron that acts as the receptive surface, bringing signals from other neurons toward the cell body.

A

Dendrites

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6
Q

What is the function of dendrites in a neuron?

A

act as the receptive surface, bringing signals from other neurons toward the cell body.

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7
Q

What are the three (3) types of neurons?

A
  • Sensory (afferent)
  • motor (efferent)
  • interneurons.
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8
Q

A type/functional unit of a neuron that conducts signals away from the cell body and carries information for long distances with high fidelity and without loss.

A

Axon

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9
Q

What is the function of axons in a neuron?

A

conduct signals away from the cell body and carry information for long distances with high fidelity and without loss.

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10
Q

Where are the motor-neuron dendrites and soma innervated?

A

On the surface membrane

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11
Q

What initiates an action potential (nerve impulse) in a neuron?

A

Soma

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12
Q

What is the role of the soma in signal transmission?

A

The soma integrates input to initiate an action potential (AP-nerve impulse).

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13
Q

Where is the action potential carried from in a neuron?

A

The action potential is carried from the spike-initiating zone near the axon hillock to the axon terminal.

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14
Q

Where does the action potential travel to in motor neurons?

A

It travels to skeletal muscle cells or glands.

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15
Q
  • It is the electrical potential difference across the cell membrane.
  • difference in electric potential between the interior and the exterior of a biological cell.
  • the result of an excess of negative charges on one side of the plasma membrane and positive charges on the other side.
  • a source of potential energy to move molecules across membranes.
A

Membrane potential (Vm)

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16
Q

What is membrane potential?

A
  • It is the electrical potential difference across the cell membrane.
  • difference in electric potential between the interior and the exterior of a biological cell.
  • the result of an excess of negative charges on one side of the plasma membrane and positive charges on the
    other side.
  • a source of potential energy to move molecules across membranes.
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17
Q

What causes the membrane potential in a neuron?

A

The membrane potential is caused by different concentrations of K+, Na+, and Cl- ions on each side of the cell membrane.

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18
Q

What is the typical range of membrane potential in neurons?

A

between -60 mV and -80 mV

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19
Q

What is the membrane potential a source of?

A

It is a source of potential energy to move molecules across membranes.

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20
Q

How do excitable cells (cells that generate and conduct electrical impulses) use membrane potential?

A

as communication signals

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21
Q

Why is membrane potential critical for cells?

A

Allows coordinated movements of cells and organisms.

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22
Q

Does every cell have a membrane potential?

A

Yes, every cell has a voltage or membrane potential across its plasma membrane.

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23
Q

What creates the membrane potential in a cell?

A

It is a localized electrical gradient, with anions concentrated inside the cell and cations concentrated in the extracellular fluid.

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24
Q

What are the two factors that influence potential difference?

A
  • concentration gradient for an ion
  • membrane’s permeability to that ion.
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25
Q

How is membrane potential measured?

A

Using a microelectrode connected to a reference electrode via a voltmeter.

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26
Q

What is the typical resting potential of an unstimulated cell?

A

Approximately -70mV.

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27
Q

In which direction does K+ move?

A

K+ moves outward.

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28
Q

In which direction does Na+ move?

A

Na+ moves inward.

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29
Q

Does Cl- have a gradient for movement?

A

No, Cl- has no gradient for movement.

30
Q

It means there are equal numbers of anions and cations.

A

Electroneutral

31
Q

What does “electroneutral” mean?

A

It means there are equal numbers of anions and cations.

32
Q

What balances the outward concentration gradient?

A

The inward electrical gradient.

33
Q

What happens when potassium ions move out of the cell?

A

It results in a region of electronegativity inside the cell and electropositivity outside.

34
Q

What is the effect of excess negative charge inside the cell?

A

It draws positive charges into the cell.

35
Q

What happens as more potassium leaves the cell?

A

The electrical force increases until it balances the driving force from the potassium concentration gradient.

36
Q

The membrane potential at which the electrical force and concentration gradient for a specific ion balance each other.

A

Equilibrium potential (Eion)

37
Q

What is an Equilibrium potential (Eion)?

A

The membrane potential at which the electrical force and concentration gradient for a specific ion balance each other.

38
Q

How many ions can move across the membrane to achieve equilibrium?

A

Eion (equilibrium potential) = Vm (membrane potential)
- Only a single ion can move across the membrane.

39
Q

What is the Nernst Equation?

A

Ex = RT/zF · ln ([X]out/[X]in)
R = gas constant
T = temperature in K
F = Faraday’s constant (23,062 cal/Vol-mol)
z = valence of ion
X – molar concentration of the ion

40
Q

It calculates the membrane potential considering the permeability and concentration of all relevant ions.

A

Goldman-Hodgkin-Katz equation

41
Q

What is the principal intracellular cation?

A

K+ (Potassium)

42
Q

What is the principal extracellular cation?

A

Na+ (Sodium)

43
Q

What are the principal intracellular anions?

A

Proteins, amino acids, sulfate, and phosphate

44
Q

What is the principal extracellular anion?

A

Cl– (Chlorine ion)

45
Q

At resting potential, where is the concentration of K+ greater? Where is the concentration of Na+ greater?

A
  • Concentration of K+ is greater inside the cell
  • Concentration of Na+ is greater outside the cell
46
Q

What do sodium-potassium pumps use to maintain K+ and Na+ gradients?

A

energy of ATP

47
Q

What does the opening of ion channels in the plasma membrane convert?

A

Chemical potential to electrical potential

48
Q

What type of channels are more open at resting potential in a neuron?

A

K+ channels

49
Q

What happens to K+ at resting potential in a neuron?

A

K+ diffuses out of the cell

50
Q

What contributes to the negative charge within a neuron at resting potential?

A

Anions trapped inside the cell

51
Q

A gate that allows ions to diffuse across the plasma membrane; they are always open.

A

non-gated ion channels

52
Q

What do non-gated ion channels do?

A

Allow ions to diffuse across the plasma membrane; they are always open.

53
Q

How do excitable cells generate large changes in their membrane potential?

A

By opening or closing gated ion channels in response to stimuli.

54
Q

What happens when ion channels open or close?

A

The membrane’s permeability to particular ions changes, altering the membrane potential.

55
Q

What are the two (2) types of gated ions?

A
  • Chemically-gated ion channel
  • Voltage-gated ion channel
56
Q

An ion channel that opens or closes in response to a chemical stimulus (ligand-gated).

A

chemically-gated ion channel

57
Q

What is a chemically-gated ion channel?

A

An ion channel that opens or closes in response to a chemical stimulus (ligand-gated).

58
Q

An ion channel that opens or closes in response to a change in membrane potential.

A

voltage-gated ion channel

59
Q

What is a voltage-gated ion channel?

A

An ion channel that opens or closes in response to a change in membrane potential.

60
Q

What do changes in membrane potential of a neuron give rise to?

A

Nerve impulses.

61
Q

Changes in membrane potential where the magnitude of change varies with the strength of the stimulus.

A

Graded Potential

62
Q

What is a graded potential?

A

Changes in membrane potential where the magnitude of change varies with the strength of the stimulus.

63
Q

What are the two (2) types of Graded Potential?

A
  • Hyperpolarization
  • Depolarization
64
Q

What type of graded potential? Gated K+ channels open, K+ diffuses out of the cell, and the membrane potential becomes more negative.

A

hyperpolarization

65
Q

What happens during hyperpolarization?

A

Gated K+ channels open, K+ diffuses out of the cell, and the membrane potential becomes more negative.

66
Q

What type of graded potential? Gated Na+ channels open, Na+ diffuses into the cell, and the membrane potential becomes less negative.

A

Depolarization

67
Q

What happens during depolarization?

A

Gated Na+ channels open, Na+ diffuses into the cell, and the membrane potential becomes less negative.

68
Q
  • It is an “all or nothing” response triggered when the threshold potential is reached.
  • Depolarization that results in graded potentials summing to approximately -55mV, achieving the threshold potential.
A

Action potential

69
Q

What is the action potential’s characteristic response? What triggers an action potential?

A
  • It is an “all or nothing” response triggered when the threshold potential is reached.
  • Depolarization that results in graded potentials summing to approximately -55mV, achieving the threshold potential.
70
Q

What are the two (2) voltage-gated Na+ channels? (What is their function)

A
  • closed activation gates open rapidly in response to
    depolarization
  • open inactivation gates close slowly in response to
    depolarization
71
Q

What is this period?
* A temporary inactivation of the Na+ channels.
* After an action potential, a second action potential cannot be initiated.

A

Refractory period

72
Q

What is a refractory period?

A
  • A temporary inactivation of the Na+ channels.
  • After an action potential, a second action potential cannot be initiated.

General Physiology (9 decks)

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