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CBNS106 > Lecture 3 > Flashcards

Lecture 3 Flashcards

1
Q

What neuron is associated with an afferent nerve?

A

Sensory neuron

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2
Q

What neuron is associated with an efferent nerve?

A

Motor neuron

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3
Q

What is membrane potential (Vm)?

A

difference in electrical charge across the membrane

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4
Q

What is membrane potential when neuron is at rest?

A

steady negative electrical potential (-65 mV)

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5
Q

What is electrical potential?

A

the force exerted on a charged particle (ion)

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6
Q

How is the resting membrane potential established and maintained?

A

Charge separation: neuronal membrane
Selective permeability: ion channel proteins
Concentration gradients: ion pumps

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7
Q

What’s the key ingredient and feature in the cytosol and extracellular fluid?

A

Water! It’s a polar solvent

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8
Q

What (besides water) is in the cytosol and extracellular fluid?

A

Ions
- cations: net positive charge
- anions: net negative charge
- hydrophilic!!

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9
Q

What’s the main features of the phospholipid bilayer?

A

-Hydrophobic lipids (tails)
- Hydrophilic phosphate groups (head)

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10
Q

How does the phospholipid bilayer act as a wall?

A

Ions hydrated in solution can’t pass through the hydrophobic core of the bilayer

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11
Q

What are proteins made from and where can they be found?

A

Made from amino acids
found in: enzymes, cytoskeletal elements, receptors, ion channels

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12
Q

What is the role of transmembrane proteins?

A
  • control resting membrane potential and action potential
  • control synaptic transmission
  • control extracellular to intracellular signaling - control
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13
Q

What is the structure of proteins?

A

many amino acids linked via peptide bonds to form polypeptide chains
- r groups alternate sides

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14
Q

What are the 4 levels of protein structure?

A

1) Primary: polypeptide chain
2) Secondary: coiling into alpha helix and beta-sheets
3) Tertiary: 3D folding of the coils and beta-sheets
4) Quaternary: different polypeptides bonding together

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15
Q

What are channel proteins and their role?

A

Polar R groups exposed to the cytosol or extracellular fluid and nonpolar t groups in the membrane
- ion selectivity and gating

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16
Q

What are the 3 types of ion channels and what do they affect?

A

1) Voltage gated: contribute to action potential
2) Ligand Gated: contribute to alterations in post-synaptic potentials
3) Leak: alter resting membrane potential

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17
Q

What is the role of Ion pumps?

A
  • critical for establishing cellular concentration gradients
  • formed by membrane-spanning proteins
  • use energy from ATP breakdown
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18
Q

What does the sodium-potassium pump work?

A

(321NoKiA)
3 Na+ out
2 K+ in
1 ATP used
- uses ~70% of the total amount of ATP in the brain

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19
Q

Define diffusion force.

A

force on an ion due to its concentration gradient
- doesn’t change significantly under physiological conditions

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20
Q

Define electrostatic force.

A

force on an ion produced by the membrane voltage
- amount and direction of the force is a function of the membrane voltage and the charge of the ion

21
Q

Define equilibrium potential

A

voltage that exactly offsets the diffusional force of the ion
- calculated by the Nernst Equation

22
Q

Define driving force.

A

sum of the diffusion and electrostatic forces
- membrane voltage minus ionic Eion)
- controls the rate of ion flux if the membrane is permeable to the ion
- ion flux alters membrane voltage

23
Q

Define ion flux.

A

mechanism by which membrane potential is changed.
- controlled by driving force of an ion and permeability of the membrane to that ion

24
Q

What is the law of permeability?

A

membrane potential is always driven toward the equilibrium potential of the ion to which the membrane is most permeable

25
Q

Define diffusion.

A
  • dissolved ions distribute evenly
  • Ions flow down concentration gradient:
    – Channels are permeable to specific ions
    – Concentration gradient exists across the membrane
26
Q

What’s Ohm’s Law?

A

I=V/R
V=IR
I: Electrical current
V: Electrical potential
R: Resistance

27
Q

What does equilibrium potential indicate?

A
  • No net movement of ions when separated by a phospholipid membrane
  • equilibrium reached with K+ channels in the phospholipid bilayer
  • Electrical potential difference that exactly balances ionic concentration gradient
28
Q

How do changes in ionic concentrations affect Vm?

A

Large changes in Vm can occur even with super small changes in ionic concentrations

29
Q

Are electrical charges balanced from the inside or outside?

A

Inside and outside membrane surfaces

30
Q

How is the rate of movement of ions across membrane calculated?

A

Determined by driving force
- driving force = Vm-Eion (membrane potential - equilibrium potential)

31
Q

How can equilibrium potential be determined in concentration difference is known?

A

Nernst Equation
Eion = 2.303 RT/zF log [ion]o/[ion]in

32
Q

What’s the relationship between charge and equilibrium potential?

A

Reversely proportional: an ion with twice the charge will have twice the Eion

33
Q

Complete the following for K+:
Concentration outside in mM
Concentration inside in mM
Ratio out:in
Eion at 37C

A

Concentration outside in mM: 5
Concentration inside in mM: 100
Ratio out:in: 1:20
Eion at 37C: -80 mV

34
Q

Complete the following for Na+:
Concentration outside in mM
Concentration inside in mM
Ratio out:in
Eion at 37C

A

Concentration outside in mM: 150
Concentration inside in mM: 15
Ratio out:in: 10:1
Eion at 37C: 62 mV

35
Q

Complete the following for Ca++:
Concentration outside in mM
Concentration inside in mM
Ratio out:in
Eion at 37C

A

Concentration outside in mM: 2
Concentration inside in mM: 0.0002
Ratio out:in: 10000:1
Eion at 37C: 123 mV

36
Q

Complete the following for Cl-:
Concentration outside in mM
Concentration inside in mM
Ratio out:in
Eion at 37C

A

Concentration outside in mM: 150
Concentration inside in mM: 13
Ratio out:in: 11.5:1
Eion at 37C: -65 mV

37
Q

Nernst equation for potassium?

A

61.54 x log [ion]out/[ion]in

38
Q

Nernst equation for sodium?

A

61.54 x log [ion]out/[ion]in

39
Q

Nernst equation for chloride?

A

-61.54 x log [ion]out/[ion]in

40
Q

Nernst equation for calcium?

A

30.77 x log [ion]out/[ion]in

41
Q

Which direction is membrane potential driven towards?

A

Towards the equilibrium potential of the ion to which the membrane is most permeable

42
Q

What is the theoretical value? The actual potential? When are they equal?

A

Individual ion equilibrium potentials = theoretical
Membrane potential = actual potential
They are the same if the membrane is permeable only to that ion

43
Q

What is the order of permeability?

A

K+&raquo_space; Cl-&raquo_space; Na+

44
Q

When do you use Goldman Equation?

A

To calculate actual resting membrane potential if relative ion permeability is known

45
Q

What is the default state of the K+ leak channel? Where does it exist? What does it result in?

A

Default state: open
Exists in all zones of the neuronal membrane
Results in a high resting permeability to K+ (determines resting membrane potential)

46
Q

What’s the structure of the K+ channels?

A

4 subunits

47
Q

What does increased extracellular K+ lead to?

A

depolarization of the membrane

48
Q

What’s the goldman equation?

A

61.54 x log (P[K+]out + P[Na+]out + P[Cl-]in)/(P[K+]in + P[Na+]in + P[Cl-]out)
P = relative membrane permeability

CBNS106 (9 decks)

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