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Neuroscience > Channels and Transporters Lec04 > Flashcards

Channels and Transporters Lec04 Flashcards

1
Q

what 3 things did hodgkin and huxleys voltage clamp experiement predict?

A
  1. sepearete na and k channels
  2. voltage sensors in channels
  3. high conductance of channels to specific ions
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2
Q

what happens once the patch clampvoltage reaches + 52 mv

A

early inward Na current is missing

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3
Q

what happens once the patch clampvoltage reaches + 65+ mv

A

early inward Na reverses to outward instead of inward

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4
Q

outward K current increases in magnitudie as the the voltage becomes more

A

positive

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5
Q

patch clamp technieque records

A

microscopic currents (current flowing through a single membrane channel due to depolarization)

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6
Q

what are macroscopic currents due to?

A

current flow through may channels

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7
Q

what did patch clamp recording show?

A

provided evidence for single channels

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8
Q

in channels, there is a fast switch between

A

open and close states

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9
Q

In response to depolarizing effect from the pipette, single channels open and close in a ____ fashion

A

_ all or none_ fashion that is random or stochastic in nature

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10
Q

what does the probability of opening a channel depend on?

A

the stimulus

depolarization increases the proability a channel will be opened

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11
Q

what is gating? what does it involve?

A

gating is the transition between open and closed states

involves a temporary conformational change in the channels structure

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12
Q

what does macroscropic current arise from?

A

the aggregate effects of THOUSANDS of microscopic currents

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13
Q

there is a close correlation of the____ of macroscopic and the sum of many trials of microscopic currents

A

time course

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14
Q

what is different about K channel and Na channel properties?

A

K channels have longer latency time and longer duration

also obviously different dierection

(Na on left, K on right)

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15
Q

on average the K+ channels tend to be an ____ state while the membrane is depolarized

A

open state (this results in a more sustained response)

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16
Q

most cns neurons ahve multiple ___ channels with different characteristics

A

potassium

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17
Q

charactersitics that vary with K channels

A
  1. low voltage vs. high voltage activation (voltage dependence)
  2. how fast the population reaches maximum conductance (rate of activation)
  3. how fast they inactivate (some dont even inactivate)
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18
Q

what is important about the varying rates of K channel inactivation

A

inactivation properties

produce a diversity of spike waveforms and spike patterns for different cells

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19
Q

Fast AHP ____ action potential

A

shortens

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20
Q

FAST AHP involves ___ repolarization

A

fast

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21
Q

when does fast AHP affect the early spike frequency

A

at very high frequencies

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22
Q

what does medium AHP control

A

controls early interspike interval

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23
Q

what does medium AHP control

A
  1. early spike frequency adaption (slowly activating by Ca entry)
  2. late spike frequency adaption
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24
Q

BK K+ channels have ___ inactivation

A

fast

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25
Q

___ and ___ are nonainactivating K channels

A

IK and SK

26
Q

what do slow AHP do?

A

limits firing frequency by an unkwnon channels

27
Q

order of channel activation

A
28
Q

what is the order of K channel activation

A
  1. Ka and Kdr channels first open
  2. Kbk channels open

3/ other known and unknown K channels open

29
Q

large number of ion channel genes create neurons with diverse ___

A

electrical properties

30
Q

fast AHP occurs in ___ seconds

A

2-5 ms

31
Q

medium AHP occurs in ___ seconds

A

10-100 ms

32
Q

slow AHP occurs in ___ seconds

A

100-3000 ms

33
Q

inactivation pattern of Kv2.1 channels?

A

show little inactivation

34
Q

inactivation pattern of Kv4.1 channels?

A

inactivate rapdily after depolarization

35
Q

when do inward rectifers allow more current flow?

A

during hyperpolarization

36
Q

why do so many genes encode K+ channels?

A

activation, gating, inactivation

37
Q

shape complex electrical responses influence

A
  1. duration of AP
  2. resting membrane potential
38
Q

TheC a++ activated K+ channel opens in response to

A

increasedintracellularCa++ and sometimes to membrane depolarization.

39
Q

the ___ of ion channels is key to developing new therapeutics for CNS disorders

A

diversity

40
Q

what do channelpathies result from?

A

they happen due to mutations in channel genes

41
Q

channelpathies in voltage gated Ca channels

A

congential stationary night blindness

familial hemiplegic migraine

episodic ataxia type 2

42
Q

channelpathies in Na channels

A

generalized epilepsy with febrile seizures

43
Q

channelpathies in K channels

A

benign familial neonatal convulsion

44
Q

channelpathy that causes_ congential stationary night blindness_

A

Ca

45
Q

channelpathy that causes_ generalized epilepsy with febrile seizures_

A

na

46
Q

channelpathy that causes_ familial hemiplegic migraine_

A

Ca channel

47
Q

channelpathy that causes benign familial neonatal convulsion

A

K

48
Q

what toxins block Na channels?

A

ttx and saxitoxin

49
Q

what toxins inactivate Na channels?

A

Batrachotoxin (frogs)

50
Q

what does a-toxin do?

A

prolongs the duration of Na channels

51
Q

what does b-toxins do?

A

shift voltage activation of Na channels

52
Q

which toxins blod K channels?

A

apaminin (bees) and dendrotoxin (wasps)

53
Q

what does TEA block?

A

K channels and AcH receptors

54
Q

What blocks Ca channels?

A

ω-conotoxins (cone snails) and ω-agatoxin (spiders) block Ca channels

55
Q

active ion transports work ___ a electrochemical gradient

A

against

56
Q

how do active ion transporters and channels differ?

A

active ion transporters having slow binding and unbinding

also are slower transport than channels

57
Q

w-conotoxins blocks ___ channels

A

n type Ca

58
Q

w-agatoxin blocks ___ channels

A

P/Q type Ca channels

59
Q

____ form a compelx with the ion they transport

A

active ion transporters

60
Q

how do ion exchangers work?

A

they don’t use energy

but trade an intracellular ion for an extracellular one

61
Q

how do ion co-transporters work?

A

transport two or more moelcules in the SAME DIRECTION ACROSS A MEMBRANE

62
Q

methods in determining channel type?

A
  1. patch clamp technique
  2. gene cloning
  3. x ray crsytallography

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