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NEUR531 > Topic 1: Resting membrane potential > Flashcards

Topic 1: Resting membrane potential Flashcards

1
Q

What does potential refer to?

A

Refers to separation of electrical charge across membrane.

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2
Q

What is having an excitable membrane mean?

A

Cells capable of generating and conducting AP (nerve and muscle cell)

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3
Q

What is it when a cell with an excitable membrane but not generating impulse?

A

At rest

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4
Q

What is the distribution of electrical charge in H20?

A

uneven

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5
Q

Is water covalently (share electron) or noncovalently bonded?

A

Covalently bonded

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6
Q

Is water polar or nonpolar?

A

Polar (things are different at each end)

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7
Q

What are atoms/molecules that have net electrical charge known as?

A

Ions

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8
Q

What bond holds 2 oppositely charged ions?

A

ionic bond

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9
Q

What are spheres of hydration?

A

Clouds of water that surround each ion

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10
Q

What are positively and negatively charged ions called, respectively?

A

Cations and anions

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11
Q

What is the building block of cell membrane?

A

Phospholipids

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12
Q

Phospholipids are long chains of…?

A

Non polar carbon atoms, bonded to hydrogen atoms also has polar phosphate group

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13
Q

What is the phospholipid “head”?

A

Polar group, containing phosphate, that hydrophilic

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14
Q

What is the phospholipid
“tail”?

A

Nonpolar, containing hydrocarbon that’s hydrophobic.

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15
Q

What’s the thickness of the neuronal membrane, and what faces outwards and inwards?

A

2 molecules thick. Hydrophilic head outward and hydrophobic tail inward

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16
Q

What is neuronal membrane called?

A

Phospholipid bilayer

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17
Q

What distinguishes neurons from other cells, in terms of protein?

A

Type and distribution of protein molecule

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18
Q

What do enzymes do?

A

Catalyse chemical reactions in neurons

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19
Q

What does the cytoskeleton do?

A

Give neuron its shape

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20
Q

What makes up proteins?

A

Assembled from various combinations of 20 amino acids

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21
Q

What are the components of amino acids

A

Has central carbon atom (alpha carbon) bonded to 4 molecular groups:
-Hydrogen atom
-An amino group (NH3+)
-Carboxyl group (COO-)
-And variable group called R group (R for residue)

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22
Q

How do difference in amino acids arise?

A

Differences in size and nature of R groups

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23
Q

What synthesizes proteins?

A

Ribosomes

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24
Q

What is the bond that connects amino acids into a chain? And how is it joined?

A

Peptide bond, joins amino group of one amino acid to carboxyl group of the next

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25
Q

Whats another name for proteins made up of a single chain of amino acids?

A

Polypeptides

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26
Q

What is the primary structure?

A

The sequence of amino acids in the polypeptide

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27
Q

What is the secondary structure?

A

coiling of the polypeptide, e.g., alpha helix

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28
Q

What is the tertiary structure

A

3-D folding of a polypeptide

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29
Q

What is quaternary structure?

A

Different polypeptides bonded together to form a larger protein

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30
Q

What is each of the different polypeptides contributing to a protein with quaternary structure called?

A

A subunit

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31
Q

Which side of phospholipid faces inwards and outward?

A

Hydrophobic portion facing inward, hydrophilic ends exposed to watery environment on either side

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32
Q

Typically, how many protein molecules for a functional ion channel?

A

4-6

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33
Q

What is ion selectivity specified by?

A

Diameter of pore and nature of R groups lining it

34
Q

What is it called when channels open and close by changes in local microenvironment of membrane?

A

Gating

35
Q

What is considered the energy currency of cells?

A

ATP (adenosine triphosphate)

36
Q

What are ion pumps?

A

Enzymes that use the energy released by the breakdown of ATP to transport certain ions across the membrane

37
Q

What influences ionic movement through channels?

A

Diffusion and electricity

38
Q

What is diffusion?

A

The net movement of ions from regions of high concentration to regions of low concentration

39
Q

What is the concentration gradient?

A

When concentration of ions higher on one side than the other therefore will flow “down” the concentration gradient

40
Q

When does movement of ions across membrane by diffusion occur?

A

1.) The membrane has channels permeable to the ions.
2.) There is a concentration gradient across the membrane

41
Q

What is electrical current and how is it represented, and measured?

A

Movement of electrical charge, represented by symbol I and measured in units called amperes (amps)

42
Q

What is the positive direction of current by convention?

A

Defined by positive-charge movement, from anode to cathode

43
Q

What 2 important factors determine how much current will flow?

A

Electrical potential and electrical conductance

44
Q

What is electrical potential (voltage)?

A

Force exerted on a charged particle, reflects difference in charge between anode and cathode (more current will flow as this difference increases)

45
Q

How is voltage represented and measure in?

A

V and volts

46
Q

What is electrical conductance?

A

The relative ability of an electrical charge to migrate form one point to another

47
Q

How is conductance represented and measured?

A

Symbol g and units called siemens (S)

48
Q

What does conductance depend on?

A

The number of ions or electrons available to carry electrical charge.
And the ease with which these particles can travel through space

49
Q

What is electrical resistance?

A

The relative inability of an electrical charge to migrate from one point to another

50
Q

How is resistance represented and measured?

A

Symbol R, units ohms (Ω)

51
Q

What is the inverse of conductance?

A

Resistance, R=1/g

52
Q

What is the relationship between potential (V), conductance (g) and the amount of current (I) that will flow ?

A

ohm’s law, I = gV

53
Q

How are concentrations of substances expressed?

A

Number of molecules per litre of solution

54
Q

How is the number of molecules expressed?

A

In moles

55
Q

How much is one mole?

A

6.02 x 10^23 molecules

56
Q

A solution is said to be 1 Molar (M) if…

A

it has a concentration of 1 mole per litre

57
Q

What is the abbreviation of concentration?

A

Pair of brackets, [NaCl]

58
Q

What is the membrane potential?

A

Voltage across the neuronal membrane at any moment, Vm

59
Q

How can one measure Vm?

A

By inserting microelectrode into the cytosol

60
Q

How does microelectrode work?

A

Has this glass tube with extremely fine tip (0.5 micrometre), penetrate membrane of neuron, filled with electrically conductive salt solution and connected to voltmeter

61
Q

What does the voltmeter connected to microelectrode do?

A

Measures electrical potential between the tip of this microelectrode and a wire placed outside of the cell

62
Q

What is the resting potential of a typical neuron?

A

-65mV

63
Q

What is an equilibrium potential of a given ion?

A

The electrical potential difference that exactly balances the concentration gradient

64
Q

What happens at equilibrium?

A

The electrical force pulls (or pushes) ions back to counterbalance the force of diffusion, net movement across membrane ceases, happens at different potentials for different ions e.g., happens at approx. -80mV for K+ ions.

65
Q

What happens to uneven charges inside and outside the neurons next to the membrane?

A

They line up along the membrane because of electro static attraction across very thin barrier

66
Q

What is the ionic driving force?

A

Ions are driven across the membrane at a rate proportional to the difference between the membrane potential and the equilibrium potential (Vm - Eion)

67
Q

What can we calculate using the Nernst Equation?

A

The equilibrium potential

68
Q

What is the Nernst equation?

A

Eion = (RT/zF)log([iono]/[ioni])

69
Q

What ions are predominantly concentrated inside and outside of neuron?

A

K+ more inside, Na+ and Ca2+, Cl- more outside

70
Q

How do concentration gradients arise?

A

Established by actions of ion pumps in neuronal membrane.

71
Q

What is a sodium-potassium pump (aka sodium pump)?

A

Enzyme that breaks down ATP in the presence of internal Na+. Uses ATP energy to exchange 3Na+ inside to outside and 2K+ from outside to inside. Pushes ions against their concentration gradient.

72
Q

What is a calcium pump?

A

Enzyme that actively transports Ca2+ out of the cytosol across the cell membrane with energy used from ATP

73
Q

What is the Goldman equation?

A

A mathematical formula that takes into consideration the relative permeability of the membrane to different ions, to calculate equilibrium potential

74
Q

What is the molecular basis for ionic selectivity?

A

Arrangement of amino acid residues (R) that line the pore regions of the channels

75
Q

How many subunits do most potassium channels and how are they arranged?

A

4, arranged like staved of a barrel to form a pore

76
Q

Which parts of the potassium channel contributes to the selectivity filter and makes the channel permeable to mostly K+?

A

Pore loop

77
Q

What is depolatization?

A

A change in membrane potential from normal resting value (-65mV) to less negative value

78
Q

What is the blood-brain barrier

A

A specialization of the walls of brain capillaries that limits the movement of K+ (and other bloodborne substances) into the extracellular fluid

79
Q

What do Glia, particularly astrocytes do when [K+] rises?

A

They take up K+

80
Q

What would happen if extracellular [K+] got to high?

A

Depolarisations, perhaps unwanted depolarisation

81
Q

What mechanism does astrocytes have to maintain extracellular K+, and what is it referred to?

A

Have K+ pumps that concentrate K+ in their cytosol and K+ channels -> they dissipate K+ over large area by extensive network of astrocytic process, called potassium spatial buffering.

NEUR531 (9 decks)

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