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Physiology I > Lecture 3 (Membrane potentials and AP) > Flashcards

Lecture 3 (Membrane potentials and AP) Flashcards

1
Q

What are the basic parts of a neuron

A

Cell body, Dendrites, and axons

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2
Q

what is housed in the cell body of a neuron

A

The nucleus and other typical cell organells

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3
Q

Do cell body’s of neurons have voltage-gated ion channels

A

NO

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4
Q

the plasma membrane around the cell body is characterized by

A

Local potentials

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5
Q

What are dendrites

A

Dendrites are cellular extensions of the neuron

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6
Q

How many dendrites does a neuron have

A

ranges from few to many

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7
Q

How are dendrites characterized

A

presence of ligand (neurotransmitter)-gated ion channels

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8
Q

Do dendrites conduct local potentials

A

Yes

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9
Q

what is an axon

A

extension of the cell body of a neuron that is typically on the opposite side of the cell body from the dendrites

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10
Q

What is the axon covered in

A

plasma membrane (axolemma)

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11
Q

how is the axolemma characterized

A

by the presence of voltage-gated ion channels and the ability to conduct an AP

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12
Q

The distal end of the axon is characterized by

A

presence of membrane-bound vesicles filled with neurotransmitter molecules

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13
Q

What is the function of the plasmalemma

A

functions to maintain separate intracellular and extracellular environments

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14
Q

what is another name for the plasmalemma

A

The cell membrane

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15
Q

where are sodium and chloride ions more concentrated

A

Outside the cell

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16
Q

Where are potassium ions most concentrated

A

Inside the cell

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17
Q

what is a diffusion potential

A

caused by an ion concentration difference on either side of a membrane

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18
Q

What is Nernst potential

A

The diffusion potential level across a membrane that exactly opposes the net diffusion of a particular ion through the membrane

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19
Q

what is the electrical dipole layer

A

dichotomous distribution of ions on either side of the membrane represents a voltage change

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20
Q

When is a voltage change recorded

A

only when the recording electrode passes through an electrical dipole layer

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21
Q

what is the Nernst equation

A 
E=2.3RT/FlogCout/Cin
E- difference in the electrical potential between inside and outside the neuron
R- Universal gas constant
T- absolute temp
F-Faradays constant
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22
Q

What is the Nernst equation used for

A

Measuring one type of ion at a time
- determines the diffusion potential across a membrane that exactly opposes the net diffusion of a particular ion through the membrane

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23
Q

what is used to measure the combined potential for more than one type of ion

A

Goldman equation may be used

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24
Q

What are the assumptions of the Nernst Equation

A

Equation can only be used for one ion at a time

  • membrane must be completely permeable to that ion
  • Ion must be at equilibrium
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25
Q

EMF equation

A

EMF=Eion= z(61.5) x log [(ion]outside/[ion]inside)
z- valence of ion
it is a simplified version of the Nernst equation

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26
Q

How does the sodium potassium pump work

A

secondary active transport

pumps 3 Na out and 2K+ in

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27
Q

what is the resting potential caused by potassium ion alone

A

-94mV

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28
Q

What is the resting potential caused by both potassium and sodium ions

A

-86mV

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29
Q

What is the resting potential caused by sodium, potassium, and Sodium potassium pump -

A

-90mV

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30
Q

What is the resting potential caused by Na alone

A

+61mV

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31
Q

Action potential characteristics

A
  • all-or- none, it will either occur or not occur
  • it is self-propagating: each region of depolarization serves to generate action potentials on either side
  • it is non-decremental- it does not decrease in strength
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32
Q

Voltage-gated sodium channels have how many domains

A

4

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33
Q

How are the 4 domains of voltage-gated sodium channels arranged

A

in a cylindrical configuration

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34
Q

How many hydrophobic transmembrane segments does each domain of voltage gated sodium channels have

A

6

35
Q

How many total dydrophobic transmembrane segments does the voltage-gated sodium channel have

A

4 domains with 6 a piece = 24 in total

36
Q

What are the 6 hydrophobic transmembrane segments of voltage gated sodium channels called

A

S1-S6

37
Q

What is special about S4 segment within each of the 4 domains of Voltage gated sodium channels

A

has high positive charge

38
Q

The inactivation gate is associated with an intracellular hydrophilic linkage between what which of the 4 domains that make up a voltage gated sodium channel

A

Domains 3 and 4

39
Q

how many gates do voltage gated sodium channels have

A

2

40
Q

What are the names of the gates in voltage gated sodium channels

A

activation gate and inactivation gate

41
Q

which gate(s) in voltage gated sodium channels is open at -90mV

A

The inactivation gate

42
Q

Which of the gate(s) of voltage gated sodium channels is closed at -90mV

A

Activation gate

43
Q

When are both of the gates in voltage gated sodium channels open

A

between -90mV to +35mV

44
Q

When does the Activation gate of Voltage gated sodium channels open

A

as voltage reaches -70mV to -50mV

45
Q

In voltage gated sodium channels the activation gate is opened and the inactivation gate is closed at what mV

A

+35mV to -90mV

46
Q

Explain the diameter of voltage-gated potassium channels

A

They are too small for hydrated potassium and hydrated sodium ions

47
Q

What is near the entrance of voltage-gated potassium channels

A

Selectivity filter

- loops from the pore helix that are bound to carbonyl oxygens

48
Q

how does the selectivity filter in voltage gated potassium ions work on hydrated sodium

A

Smaller hydrated ions such as sodium are not affected by the selectivity filter but are too large to pass through the potassium channel

49
Q

How does the selectivity filter of voltage-gated potassium channels work on hydrated potassium

A

larger hydrated ions such as potassium will be dehydrated by the selectivity filter, allowing the smaller “naked” potassium ion to pass through the channel

50
Q

How many gates do potassium-gated channels have

A

one

51
Q

When is the potassium-gate closed

A

At resting potential of -90mV

52
Q

When is the potassium-gate open

A

slow activation opens from +35mV to -90mV

53
Q

Is the potassium gate slow or fast opening

A

Slow

54
Q

When is the resting stage of an AP

A

-90mV

55
Q

At what stage of an AP does the membrane suddenly become permeable to sodium ions

A

The depolarization stage

56
Q

how fast do the sodium channels close

A

within a few 10,000 of a second

57
Q

what happens in the repolarization stage of an AP

A

sodium channels close

potassium channels open more than normal

58
Q

explain the positive feeback system that is in place for sodium during Ap

A

During AP the sodium membrane conductance increases with increase in sodium channel opening leads to larger influx and thus faster AP

59
Q

Does each cell have its own threshold

A

Yes

60
Q

what is the name of the activation gate

A

(m-gate)

61
Q

what is the name of the H-gate

A

inactivation gate

62
Q

which ion channels are faster potassium or sodium

A

Sodium

63
Q

ways to increase speed of propagation of AP

A 
Increasing diameter of the axon
- used by invertebrates 
Increase membrane resistance
- myelination 
-creates a capacitor effect
64
Q

What is salutatory conduction

A

jumping of current from one node to the next

65
Q

what is local potential

A

Caused by a ligand gated channel

often in dendrites

66
Q

what is threshold

A

the point at which a local potential will elicit an AP

usually -65mV

67
Q

What is the direction of propagation

A

AP travel in all directions from the point fo stimulation

68
Q

what is orthodromic direction

A

direction normally taken (toward the distal end of the axon)

69
Q

What is antidromic direction

A

Opposite of normal

toward the axon hillock, neuron cell body

70
Q

why do AP typically travel in the orthodromic direction

A

because the area behind is hyperpolarized, it is an absolute refractory period

71
Q

what is the principle lipid of myelin sheaths

A

Sphingomyelin

72
Q

What are Schwann cells

A

Cells that form the myelin sheaths in the peripheral axons

73
Q

What are the nodes of Ranvier

A

unmyelinated junctions between schwann cells

74
Q

Why does myelination increase velocity of transmission

A

allows 100x less loss of ions and requires little energy fro repolarization

75
Q

where do AP occur in myelinated axons

A

at the nodes of Ranvier

76
Q

why do small diameter fibers conduct action potentials slower than large diameter fibers

A

Small diameter fibers have an increase internal resistance

77
Q

what is the absolute refractory period

A

period during which a second AP cannot be elicited even with a strong stimulus

78
Q

where is the energy derived during the absolute refractory period

A

the breakdown of ATP

79
Q

what is the relative refractory period

A

period when a stronger than normal stimulus can cause AP

80
Q

what affect do high potassium concentrations have on AP

A

They block sodium channels and thus make AP difficult

81
Q

Which of the following types of neurons would transmit an AP the fastest

A

Large diameter, myelinated

82
Q

salutatory conduction is characteristic of which part of a typical neuron

A

Axon

83
Q

a selectivity filter with carbonyl oxygens is associated with what kind of ion channels

A

Potassium

84
Q

The resting potential for a typical neuron, such as a motor neuron, is best represented by what potential

A

-90mV

Physiology I (8 decks)

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