Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

Medical Physiology > L2: Resting Membrane Potential > Flashcards

L2: Resting Membrane Potential Flashcards

You may prefer our related Brainscape-certified flashcards:
USMLE® Step 1 flashcards
1
Q

Forces acting on ions separated by a membrane

A
  1. ) Chemical driving force: ion’s own chemical concentration gradient exerts this force on this ion causing the ion to move from area of high concentration to area of low concentration. This force is only the result of the ion’s concentration gradient
  2. ) Electrical driving force: as ion’s move down their chemical concentration gradient, they generate electrical forces depending on their charge and the amount of negative/positive charges inside relative to outside
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

What does the electrical force exert on positive ions when the membrane potential is negative? Positive? What will this force do to negative ions?

A
  • When negative: positive cations are drawn into the cell, negative ions pushed out
  • When positive: positive cations are pushed out of the cell, negative ions brought in
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

What does the chemical driving force for: K, Na, Cl- and Ca do to these ions given the EC and IC concentrations seen in vitro?

A
  • K: pushes it out
  • Na: brings it in
  • Cl: brings it in
  • Ca: brings it in
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

Is the inside of a cell negative or positive in relation to the outside?

A
  • Negative
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q 
Describe the results of the following movements to the membrane potential of a cell:
A.)	positive ion moving out
B.)	positive ion moving in
C.)	negative ion moving in
D.)	negative ion moving out
A
  • A.) more negative membrane potential
  • B.) less negative membrane potential
  • C.) more negative membrane potential
  • D.) less negative membrane potential
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

True/False. The Equilibrium potential gives us the strength of the electrical force on the ion.

A
  • False, gives us the strength of the chemical force on the ion d/t concentration gradient
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

What does electrochemical equilibrium E(sub)x represent?

A
  • Voltage where chemical driving force against ion equals electrical driving force
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

What is the idea of net charge neutrality?

A
  • Macroscopic regions of a solution must have equal numbers of positive and negative charges, therefore membrane potential is only generated by an extremely small charge imbalance across a membrane and represent a small proportion of ions
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

What channels and ion primarily determines the resting membrane potential of a cell?

A
  • More K channels on cells in real life, therefore K ion. Vrest sits between ENa and EK, but much closer to Ek
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

True/False. At rest, there is a constant efflux of K out of the cell and a constant efflux of Na into the cell with a net flux of K out.

A
  • False, the efflux and influx described here is occurring, but the are counterbalanced to no net ion flux. Pump functions to restore ion concentration gradients while these fluxes are happening.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

Why is the sodium/potassium pump electrogenic?

A
  • Pumps 3 sodiums out for every 2 potassiums in – therefore creating a net negative.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

What is the Nernst potential?

A
  • Membrane potential that would prevent any net diffusion of the ion
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

Nernst equation

A

E(ion) = - RT/zF ln([inside]/[outside]) = - 60/z log([inside]/[outside])

  • For positive ion, should be +ve
  • For negative ion, should be –ve
  • ** Z = charge
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

What does +ve equilibrium potential mean for direction a positive ion would move?

A
  • Positive ion would move inwards making the inside of the cell positive. Remember the positive E in this case refers to the inside of the cell
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

What does –ve equilibrium potential mean for direction a positive ion would move?

A
  • Positive ion would move outwards leaving the inside of the cell negative. Remember the negative E in this case refers to the inside of the cell.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

Calculate: a.) log1, b.) log10, c.) log100, d.) log0.1

A
  • a.) 0
  • b.) 1
  • c.) 2
  • d.) -1
    • just remember log base 10 is taking the number in front of it and looking at its x10 power. 10 can be written 1.0 x 10^1, so answer to log10 = 1. 0.1 can be written 1 x 10^-1, so log0.1 = -1
17
Q

If K was 100 times higher inside the cell than outside, what would happen to its equilibrium potential? What is the effect of this on the RMP?

A
  • Esub(K)= -60/z log (100/1) = -60/1 x 2 = -120 mV
  • Concentration gradient would be steeper d/t hypokalemic condition and K would strongly want to move outside of the cell causing hyperpolarization.
18
Q

If Na was 10 times higher inside the cell than outside, what would happen to its equilibrium potential? What is the effect of this on the RMP?

A
  • Esub(Na)= -60/z log (10/1) = -60 x 1 = -60 mV
  • Concentration gradient would be reversed d/t hyponatremic condition and K would strongly want to move outside of the cell causing hyperpolarization.
19
Q

Limitation of Nernst equation? Alternative?

A
  • Calculates equilibrium potential of single ion without taking into account the relative permeability of membrane to an ion.
  • Goldman-Hodgkin-Katz equation can calculate equilibrium potential across a membrane by using multiple ions and also taking into account the relative permeability of the membrane to said ions.
20
Q

What will happen to the membrane potential in a cell if the EC fluid starts increasing concentration of K?

A
  • Concentration gradient slope for K will become less steep and K will want to stay in the cell, causing the inside of the cell to be less negative, ie. Cell will depolarize.
21
Q

What is normal blood potassium level? What occurs when these levels occurs?

A
  • 3.5-5.0 mM

- hyperkalemia = increase – leads to abnormal function of muscle, heart and nerve

22
Q

What is the contribution of calcium to RMP?

A
  • Does not contribute to RMP as cell is impermeable to it at rest
23
Q

As the external concentration of K is raised, the EsubK becomes: 1.) more negative / less negative. This makes the membrane potential become 2.) more negative / less negative.

A
  • 1.) less negative (K stays inside, making inside more positive or less negative)
  • 2.) less negative (depolarizes the cell)
24
Q

As the external concentration of K decreases, the EsubK becomes: 1.) more negative / less negative. This makes the membrane potential become 2.) more negative / less negative.

A
  • 1.) more negative (K is driven out cell more, making inside more negative/less positive)
  • 2.) more negative (hyperpolarizes the cell)
25
Q

If the extracellular concentration of Na is lowered, the EsubNa becomes: 1.) increased / decreased. This makes the membrane potential become 2.) greatly more negative or slightly more negative.

A
  • 1.) decreased (Na doesn’t have strong drive to move inside, therefore making inside more negative)
  • 2.) slightly more negative (not as many Na channels in membrane, so overall effect on membrane potential is lower in comparison to K)
26
Q

If the extracellular concentration of Na is increased. The EsubNa becomes: 1.) increased or decreased. This makes the membrane potential become 2.) greatly less negative or slightly less negative.

A
  • 1.) increased (Na has stronger drive to enter cell making inside less negative)
  • 2.) slightly less negative (not as many Na channels in membrane, so overall effect on membrane potential is lower in comparison to K)
27
Q

What is the effect of chloride ions on the RMP of a cell type that is not pumping chloride into or out of itself?

A
  • Chloride is usually high outside, low inside

- Flux of chloride therefore follows RMP since there is no driving force, so it has no contribution to RMP

28
Q

What is the effect of chloride ions on the RMP in a neuron that is actively pumping chloride ions outside of the cell?

A
  • Chloride high outside, low inside
  • When actively being pumped out, negative ions are leaving the cell and the equilibrium potential is driven downwards, pulling the RMP towards hyperpolarized state
29
Q

What are the directions for the chemical and electrical forces on potassium when a neuron is at its RMP of -65mV? Which force is stronger if any assuming EsubK is -90 mV?
A. Both the chemical and electrical forces push K into the cell
B. Both the chemical and electrical forces push K out of the cell
C. The electrical force pushes K in and the chemical force pushes it out
D. The electrical force pushes K out and the chemical forces pushes it into the cell
E. Since the cell is at rest, there are no chemical or electrical forces on K

A
  • C. Vm represents electrical driving force at -65. Ek represents chemical driving force at -90 mV, therefore chemical driving force from 0 is 90 and stronger.
30
Q

Function of ouabain?

A
  • Inhibits Na/K ATPase. Given time, cells eventually lose resting membrane potential
31
Q

What happens to the membrane potential as the relative permeability to an ion increases?

A
  • Membrane potential moves closer to equilibrium potential of that ion and vice versa.
32
Q

What is the effect of sodium being pumped out of cell in terms of osmotic pressure?

A
  • Water follows sodium so osmotic pressure in cytoplasm decreases and increases in ECF
33
Q

Give rough values for equilibrium potentials for sodium, potassium, chloride and calcium in a nerve and muscle cell

A
  • Sodium = +65 mV
  • Potassium = -85 mV
  • Chloride = -85 mV
  • Calcium = +120 mV

Medical Physiology (10 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions