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Neuroscience > Chapter 4 > Flashcards

Chapter 4 Flashcards

1
Q

Action potential is also called…

A
  • Spike
  • Nerve impulse
  • Discharge
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2
Q

Action potential is a rapid…

A

Reversal of membrane potential where the inside becomes positively charged with respect to the outside

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3
Q

What is synaptic transmission?

A

Synaptic transmission is the transfer of information from neuron to neuron

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4
Q

How do action potentials affect information transfer?

A

The frequency and pattern of action potentials constitute the code used by neurons to transfer information from one location to another

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5
Q

Action potential is responsible for

A

Conveying information over long distances

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6
Q

What is depolarization?

A

Depolarization is when the membrane voltage becomes more positive

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7
Q

What is hyperpolarization?

A

Hyperpolarization is when the membrane voltage becomes more negative

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8
Q

Positive ion influx results in…

A

Depolarization

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9
Q

Positive ion efflux results in…

A

Hyperpolarization

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10
Q

Negative ion influx results in…

A

Hyperpolarization

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11
Q

Negative ion efflux results in…

A

Depolarization

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12
Q

How is action potential generated?

A

Action potential is generated through a depolarizing current of membrane beyond threshold
- Occurs naturally via excitatory synaptic transmission
- Occurs artificially via current injection into a neuron with a microelectrode

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13
Q

If injected current does not depolarize the membrane to threshold…

A

No action potentials will be generated

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14
Q

If injected current depolarizes the membrane beyond threshold…

A

Action potentials will be generated

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15
Q

The action potential firing rate ____ as the depolarizing rate ____

A

Increases; increases

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16
Q

Neurons are electrically ___

A

Active

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17
Q

Glia are electrically ____

A

Silent

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18
Q

Explain the process of a chain reaction of action potential with a foot puncture:

A

Foot puncture, stretch membrane of nerve fibers
- Opens Na+ permeable channels-> Na+ influx-> depolarized membrane->reaches threshold-> action potential

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19
Q

Action potential graph

A

*Undershoot occurs after hyperpolarization

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20
Q

Characteristics of action potentials

A
  1. Have a threshold for initiation
  2. All or nothing (below threshold = none, above threshold = all)
  3. Always depolarizing
  4. Constant amplitude
  5. Constant duration
  6. Propagate without decrement
  7. Have a two part refractory period (absolute: during falling phase, relative: during undershoot)
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21
Q

What is membrane current?

A

Net movement of K+ across membrane

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22
Q

Potassium channel number is ____ to electrical conductance

A

Proportional

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23
Q

Membrane potassium current consists of…

A

Flow and driving force

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24
Q

What is the rising phase?

A

Inward sodium current, influx of Na+ ions

25
Q

What is the falling phase?

A

Outward potassium current, efflux of K+ ions

26
Q

What are Hodgkin and Huxley known for?

A

Use of patch-clamp electrophysiology to demonstrate properties of AP

27
Q

What is the purpose of a voltage clamp?

A

“Clamp” membrane potential at any chosen value

28
Q

What does the voltage gated sodium channel consist of?

A

Transmembrane domains and ion-selective pore

29
Q

What are the 3 states of voltage gated sodium potentials?

A

Closed, open, inactivated

30
Q

Channel closing and reactivation require…

A

Negative Vm reset

31
Q

What occurs in the absolute refractory period?

A

Channels are inactivated

32
Q

What is the extracellular concentration of Na+?

A

150 mM

33
Q

What is the intracellular concentration of Na+?

A

15 mM

34
Q

What is the extracellular concentration of K+?

A

5 mM

35
Q

What is the intracellular concentration of K+?

A

100 mM

36
Q

What are some toxins that target voltage gated sodium channels (VGSC)?

A
  1. Puffer fish tetrodotoxin
  2. Red tide saxitoxin
  3. Batrachotoxin
37
Q

What happens with puffer fish tetrodotoxin (TTX)?

A

Clogs Na+ permeable pore

38
Q

What happens with red tide saxitoxin?

A

Na+ channel is blocked

39
Q

What happens with batrachotoxin?

A

Inactivation so channels remain open

40
Q

What is channelopathies?

A

Generalized epilepsy, febrile seizures

41
Q

Potassium gates open ___ than sodium gates

A

Later

42
Q

Potassium conductance serves to ____ membrane potential

A

Rectify or reset

43
Q

What is the structure of VGKC’s?

A

Four separate polypeptide subunits join to form a pore

44
Q

Do voltage-gated K+ channels activate?

A

No

45
Q

What occurs at T1?

A

Voltage-gated Na+ channels open

46
Q

What occurs at T2?

A

The voltage-gated Na+ channels inactivate and K+ channels are opening

47
Q

What occurs at T3?

A

The voltage-gated K+ channels are closing, stopping K+ efflux

48
Q

What occurs during the absolute refractory period?

A

Voltage gated Na+ channels are inactivated

49
Q

What occurs during the relative refractory period?

A

It occurs during after-hyperpolarization. Voltage gated Na+ channels become reactivated, but membrane potential is below resting and would require greater depolarization current to fire another action potential than at rest

50
Q

What does the spike-initiation zone consist of?

A

Sensory nerve endings and axon hillock

51
Q

What factors influence conduction velocity?

A
  • Spread of action potential along membrane (dependent on axon structure)
  • Path of positive charge (inside axon = faster), across the axonal membrane = slower)
  • Axonal excitability (axonal diameter: bigger=faster)
  • Number of voltage gated channels
  • Myelination
52
Q

What does orthodromic mean?

A

Action potential travels in one direction (down the axon to the axon terminal)

53
Q

What does antidromic (experimental) mean?

A

Backward propagation

54
Q

What is the typical conduction velocity of propagation of action potential?

A

10 m/sec

55
Q

What is the typical length of action potential?

A

~2 msec

56
Q

Layers of myelin sheath facilitate….

A

Current flow (in conduction velocity)

57
Q

What type of conduction occurs at Nodes of Ranvier?

A

Saltatory conduction; here voltage gated sodium channels are concentrated

58
Q

What id Optogenetics?

A
  • Introduction of foreign genes: express membrane ion channels, open in response to light
    Ex: In the mouse brain, neurons firing controlled by light delivered by optic fiber
59
Q

What is the flow of neuronal signal transmition due to puncture in the skin?

A

Puncture the skin-> nerves stretch-> Na+ open-> Ap initiated and propagated->information “communicated” to the next neuron across the membrane (synaptic transmission)

Neuroscience (8 decks)

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