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physiology > Electrophysiology of the Cell Membrane > Flashcards

Electrophysiology of the Cell Membrane Flashcards

1
Q

What are the major inorganic ions that carry electrical currents (across membrane)

A

Ca 2+ , Na + , K + , Cl − , and HCO3-

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2
Q

What three integral membrane proteins are used for electric current flow

A

ion channels, electrogenic ion transporters and electrogenic ion pumps.

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3
Q

what things are involded in hormone secretion, ionic homeostasis, osmoregulation, and regulation of muscle contractility.

A

channels proteins

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4
Q

charge/lading is measured in?

A

coulombs

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5
Q

what is z for Cl-?

A

z=-1

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6
Q

what is e0?

A

unitary charge , 1.6022 × 10 −19

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7
Q

( ε r)=?

A

dielectric constant

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8
Q

( ℱ )=?

A

attractive electrostatic force

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9
Q

why cant Na move from water to inside of membrane?

A

(high ε) to the interior of a phospholipid membrane (low ε) ~36 kcal/mole. This value is 60-fold higher than molecular thermal energy at room temperature.

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10
Q

what is intracellular recording

A

The sharp tip of a microelectrode is gently inserted into the cell and measures the transmembrane potential with respect to the electrical potential of the extracellular solution, defined as ground (i.e., ψ o = 0).

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11
Q

What is the Vm of a skelatal muscle cell?

A

-90mV

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12
Q

what is E (E=Vm/a)

A

electrical field.

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13
Q

Skeletal muscle cells, cardiac cells, and neurons typically have resting membrane potentials of approximately .. to …mV; smooth-muscle cells have membrane potentials in the range of … mV; and the V m of the human erythrocyte is only about .. mV. However, certain bacteria and plant cells have transmembrane voltages as large as ….

A

Skeletal muscle cells, cardiac cells, and neurons typically have resting membrane potentials of approximately −60 to −90 mV; smooth-muscle cells have membrane potentials in the range of −55 mV; and the V m of the human erythrocyte is only about −9 mV. However, certain bacteria and plant cells have transmembrane voltages as large as −200 mV.

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14
Q

When are spectroscopic techniques used to meassure the Vm

A

very small cells such as erythrocytes, small intracellular organelles such as mitochondria, and fine processes such as the synaptic endings of neurons

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15
Q

how do spectroscopic techniques work

A

cells or membranes are labeled with an organic dye molecule and the absorption or fluorescence of the dye is monitored

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16
Q

what is another way of measuring Vm (not spectroscopic or microelectrode).

A

optically is to use cells that express genetically engineered voltage-sensing proteins that have been coupled to a modified version of the jellyfish green fluorescent protein (GFP).

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17
Q

what does the optical method for measuring Vm benefit from

A

it can see that Vm changes are similar but delayed in the more distant neural processes inaccessible to the microelectrode.

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18
Q

what 3 objects are needed for the fluorescent dye method?

A

light source
dichroic mirror
photodetector
(emmited red light changes with Vm

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19
Q

what ois resting potential

A

steady value (Vm) when the cell is not undergoing active responses

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20
Q

With what parameter does Vm have relationship?

A

Electrical field

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21
Q

what are electrogenic transporters

A

transporters that can generate a current that sets up and electric potential accros the membrane.

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22
Q

is the Na-K pump direct contribution to the Vm small or large?

A

small

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23
Q

What happens if you switch CL to SO4

A

you eliminate the contribution of anions to Vm

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24
Q

How is the Na-K pump responsible for Vm

A

indriect by generating and maintaining ion gradients

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25
Q

WHat is the planar lipid bilayer

A

artificial cell membrane

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26
Q

To what is the planar lipid bilayer similar intracellular recording or spectroscopic. and what is the main difference between PLB and the similar technieque

A

intracellular

both sides of the mebrane are accessible to manipulation

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27
Q

Why does one add a suffienct amount of a nonelectrolyte to the side with lower KCL concentration (Planar Lipid Bilayers)

A

to ellimante osmotic flow

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28
Q

What substance can you add to Planar Lipid Bilayer to eliminate osmotic flow.

A

mannitol

nonelectrolyte

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29
Q

is the planar bilayer permeable or impermeable?

A

impermeable

30
Q

what are the minimal components for generating a Vm

A

impermeable membrane
unequal ion solutions (ion gradient)
ion-selective channels (conductance pathway)

31
Q

what do ion channels do for the membrane

A

a conductance pathway lowering the resistance

32
Q

what are diffusion potential

A

the membrane potential caused by , X diffuses down its concentration gradient (in planar-bilayer)

33
Q

what is simmilar to the diffusion potential at equilibrium

A

equilibrium potential ( E X )

34
Q

what gives the nernst equation

A

equilibrium potential ( E X )

35
Q

What are the two ways to predict Vm without the discovery of ion channels

A

is to measure the movemnt of a single ion species through the membrane.
2. summing up the currents carried by each species of ions present

36
Q

what is electrodiffusion?

A

process of ion permeation through the membrane

37
Q

what is the constant vield assumption

A

the electric field (=the change in voltage with distance) is constant.

38
Q

what is the Independence principle?

A

the movement of an ion through a membrane is independent from the movement of other ions

39
Q

Px=Dx*β/ a.

what are the parameters

A

px= permeabilty coeffiecient
Dx is the diffusion coefficient in the mebrane
a= the thickness of the membrane
β is the membrane/water partition coefficient for the ion,

40
Q

what does the electrodiffusion model assume

A

homogenous membrane
constant electric field
ions move independently from one another
a constant permeabilty coeffiecient.

41
Q

what laws do we use do calculate current of a single ion (with electrodiffusion model assumptions)

A
  1. fick’s law of diffusion
  2. the movement of ions in an electric field ((electrophoresis)
  3. oHMS LAW
42
Q

What is the goldman-hodgkin katz current equations a result of

A
  1. fick’s law of diffusion
  2. the movement of ions in an electric field ((electrophoresis)
  3. oHMS LAW
43
Q

what is the Goldman-Hodgkin-Katz (GHK) current equation,

A

the constant-field assumption applied to Nernst-Planck electrodiffusion

44
Q

what is Ix

A

the rate of ions moving through a membrane (ampere)

45
Q

to what does the GHK equation relate the current of ion X?

A

internal external concentration of X, transmembrane voltage and the permability of the membrane to X

46
Q

is the inward going current negative going current or positive going current

A

negative going current

in to the cell

47
Q

is the outward going current negative going current or positive going current

A

positive going current

out of the cell

48
Q

is inward flow of CL- inward or outward current?

A

outward, because current is always direction of positive charge.

49
Q

what is the reversal potential equal to?

A

Nernst potential (Ex)

50
Q

when Vm is more negative than Vrev what will cations do

A

move inward

51
Q

when is the GHK voltage equation or the constant-field equation is valid

A

when zero net flux flowing across the membrane

52
Q

when does VM equal Vrev?

A

at resting membrane potential.

53
Q

What happens with hypoklamia to the TWIK-1 K2P channel

A

α becomes larger, causes depolarization that can trigger cardiac arrhythmia leading to cardiac arrest

54
Q

what ion and cause has a high permeability to vertebate skeletal muscle cells

A

Cl, Cl − equilibrium potential in skeletal muscle is essentially equivalent to the resting potential

55
Q

what is an EMF

A

voltage source of a battery.

electromotive force

56
Q

what is the emf of an ion

A

the equilibrium potential

57
Q

what is the variable resistor of K

A

the conductance provided by K channels

58
Q

what is a capacitor

A

a device that is capable of storing charge

59
Q

what is the capacitor of a cell

A

the lipid bilayer

60
Q

what is capacitance

A

the magnitude of the carge stoped per unit potenial difference.
in farads

61
Q

what is (ε 0 ), in capacitance

A

vacuum permittivity constant

62
Q

what is (ε r ) in capacitance

A

the relative permittivity (dielectric constant) of the medium between the two plates

63
Q

what is A in capacitiance formula

A

surface area (A) of one side of a plate

64
Q

are cell membrane potential sustained by a small or large separation of charge

A

small

65
Q

does Cl depolarize or hyperpolaryise

A

both in most cells depolarize

in skeletal cells hyper polarize

66
Q

what is the capacitative current?

A

the current that only flows when Vm is changing.

67
Q

how does a condensator (capacitor) produce current

A

when a voltage across a capacitor changes the capicator either loses or gains charge.

68
Q

what is the time constant

A

The time required for the voltage to fall to 37% of its initial value

69
Q

what is a square pulse

A

current or voltage is abruptly changed to a fixed value, held constant for a certain time, and returned to the original value.

70
Q

what does square pulse of V do to Im

A

2 brief spikes

71
Q

what does square pulse of I do to Vm

A

the voltage changes to a new value with a rounded time course determined by the RC value of the membrane.

72
Q

what is electrophoresis

A

the movement of ions in an electric field

physiology (8 decks)

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