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NPB100 > Lecture 2 > Flashcards

Lecture 2 Flashcards

Neuronal Activity, Membranes and Ion flow

1
Q

What is depolarization?

A

-Decrease in |potential|
-Membrane becomes less negative (closer to 0)
-Usually the positive slop portion of a TimexMembrane potential graph

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2
Q

What is repolarization?

A

-Returning to resting potential after depolarization
-Usually the negative slope portion from the peak to the resting potential

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3
Q

What is hyperpolarization?

A

-Increase in |potential|
-Membrane becomes more negative, further from 0
-negative slope after resting potential

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4
Q

What are the 2 types of electrical signals?

A

Graded potentials and action potentials

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5
Q

Graded potentials can be _________ or _________ potentials.

A

synaptic or receptor

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6
Q

What are action potentials triggered by?

A

Graded potentials

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7
Q

What do the proteins int he lipid bilayer cell membrane serve as?

A

receptors, channels, and transporters

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8
Q

What type of molecules can easily diffuse through membranes? Examples?

A

Small hydrophobic molecules – O2, CO2, N2, benzene

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9
Q

What type of molecules can somewhat easily diffuse through membranes? Examples?

A

Smaller uncharged polar molecules – H2O, glycerol, and ethanol

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10
Q

What type of molecules can not pass through membranes via diffusion? What is required for them to pass through?

A

-Larger uncharged polar molecules (aa’s, glucose, nucleotides – H+, Na+ K+, Cl-, Ca2+)

-special membrane proteins

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11
Q

Def of ion movement

A

Movement through diffusion - random movement of molecules

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12
Q

What is ion movement driven by? Together they form?

A

Concentration/Chemical Gradient/Forces

Electrical Gradient/Forces

Electrochemical gradient

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13
Q

Ions move from ___ to ____ due to chemical forces

A

high to low

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14
Q

Ion movement needs proteins that create (hydrophobic/hydrophilic) or electrically (unfavorable/favorable) environment

A

hydrophillic – allows hydrophillic things to enter

favorable – will more likely happen

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15
Q

Channels – (passive/active)
Carriers – (passive/active)
Pumps – (passive/active)

A

Channels and carriers are passive.. Pumps are active

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16
Q

Channels open “holes” allowing ions to diffuse (up/down) their ___________ gradients.

A

down their electrochemical gradients

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17
Q

Carriers like Na+/glucose co transporter carry ions (up/down) their electrochemical gradient.

A

down – carriers are passive

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18
Q

Which one requires energy and drives ion movement against their electrochemical gradient? – channel, carrier, or pump?

A

pump – active

19
Q

There is 5K+ and 3Cl- on both sides of the membrane. Is there an electrical gradient? Concentration gradient?

A

No concentration or electrical gradient - same concentration of types of ions on each side and same number of +/- charges on each side

20
Q

What does the nernst equation calculate? When do you use it?

A

Equilibrium Potential of an Ion (Eion) // only when only one ion is permeable

21
Q

What does Eion stand for? Ex: Ek+

A

Equilibrium potential – Equilibrium potential of K+

22
Q

When intercellular and extracellular concentrations are equal, what is Eion (equilibrium potential)?

A

0

23
Q

What is the equilibrium potential of K+? (Ek+)

A

-90mV

24
Q

When a cell is permeable to only one ion, what is the resting membrane potential of the cell equal to?

A

The Equilibrium Potential of that Ion

25
Q

What will
be the resting membrane potential be for a cell that is only permeable for Na+ (ENa+ = +50mV)? What about for K+ (EK+ = -90mV)

A

+50 / -90
RMP = Eion is ion is the only thing that’s permeable

26
Q

If the cell is permeable to BOTH Na+
and K+, and it is equally permeable. What will be the
membrane potential across the membrane of this cell?

ENa+ = +50mV
K+ = -90mV

A

Exactly between -90 and +50 – equally permeable means same numebr of channels

27
Q

If an ion has a positive charge (z = 1; K+)

a (-) equilibrium potential means that there are (more/less) ions inside

A

less

less k+ inside, (+) z == -Ek+

28
Q

If an ion has a negative charge (z = -1; Cl-)

a (+) equilibrium potential means that there are (more/less) ions outside

A

less

less cl- outside, (-) z == +Ecl-

29
Q

Overall, if you want to find the equilibrium potential of an ion, you should take into account of

A

does it have a (+/-) charge? Are there more concentration outside or inside?

30
Q

What does a (-) equilibrium potential tell us about K+? - is there more/less K+ inside? Does K+ want to leave or enter the membrane?

A

More inside – leaves membrane

31
Q

What does a (+) equilibrium potential tell us about Na+? - is there more/less Na+ inside? Does Na+ want to leave or enter the membrane?

A

Less inside – wants to enter the membrane

32
Q

T/F Leak channels are constantly open.

A

T

33
Q

In neurons, we have many more leak channels for Na+/K+/Cl-.

A

K+

34
Q

What will be the approx. membrane potential of a
neuron that has many more leak channels for K+, than Na+ and for whom ENa+=+50mV; EK+=-90mV?

A

Closer to -90mV but more (+)

35
Q

Each ion contributes to the resting potential in a manner somewhat
proportional to the ____________ of the cell to that ion

A

permeability(p)

36
Q

What does the Goldman or GHK Equation calculate? When do you use it?

A

Resting potential (Vm)– when there are multiple ions that are permeable

37
Q

What is the equilibrium potential of Cl-?

A

-70mV

38
Q

GHK equation: For positively charged ions like Na+ and K+, is it:

[out]/[in] or
[in]/[out] ?

A

[out]/[in]

39
Q

GHK equation: For negatively charged ions like Cl-, is it:

[out]/[in] or
[in]/[out] ?

A

[in]/[out]

40
Q

What 2 things is resting membrane potential (Vm) determined by?

A
  1. selective permeabilities of ions
  2. electrochemical gradients of the ions
41
Q

T/F -Resting potential is always nearest E for the most permeable ion (K+)

A

T

42
Q

What is the typical resting potential for a neuron?

A

-70mV

43
Q

Vrest = ?
Ek+ = ?
Ena+ = ?
Ecl- = ?

A

Vrest = -70mV
Ek+ = -90mV
Ena+ = +50mV
Ecl- = -70mV

44
Q

What maintains the concentration gradients across the membrane?

A

Na+/K_ ATPase pump - it actively transports Na+ and K+ ions across the cell membrane

-Ions are pushed against their concentration gradients.

-3 Na+ leave = 2K+ enter — pump
is electrogenic

NPB100 (8 decks)

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