Channels and Transporters Lec04 Flashcards Preview

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Flashcards in Channels and Transporters Lec04 Deck (62):
1

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

1. sepearete na and k channels

2. voltage sensors in channels

3. high conductance of channels to specific ions

2

what happens once the patch clampvoltage reaches + 52 mv

early inward Na current is missing

3

what happens once the patch clampvoltage reaches + 65+ mv

early inward Na reverses to outward instead of inward

4

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

positive

5

patch clamp technieque records

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

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6

what are macroscopic currents due to?

current flow through may channels

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7

what did patch clamp recording show?

provided evidence for single channels

8

in channels, there is a fast switch between

open and close states

9

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

 all or none fashion that is random or stochastic in nature

10

what does the probability of opening a channel depend on?

the stimulus 

 

depolarization increases the proability a channel will be opened

11

what is gating? what does it involve?

gating is the transition between open and closed states

involves a temporary conformational change in the channels structure

12

what does macroscropic current arise from?

the aggregate effects of THOUSANDS of microscopic currents

13

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

 time course 

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14

what is different about K channel and Na channel properties?

K channels have longer latency time and longer duration

also obviously different dierection 

(Na on left, K on right)

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15

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

open state (this results in a more sustained response)

16

most cns neurons ahve multiple ___ channels with different characteristics

potassium

17

charactersitics that vary with K channels

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)

18

what is important about the varying rates of K channel inactivation 

inactivation properties

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

19

Fast AHP ____ action potential

shortens

20

FAST AHP involves ___ repolarization

fast

21

when does fast AHP affect the early spike frequency

at very high frequencies

22

what does medium AHP control

controls early interspike interval

 

23

what does medium AHP control

1. early spike frequency adaption (slowly activating by Ca entry)

2. late spike frequency adaption

24

BK K+ channels have ___ inactivation

fast

25

___ and ___ are nonainactivating K channels 

IK and SK

26

what do slow AHP do?

limits firing frequency by an unkwnon channels

27

order of channel activation

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28

what is the order of K channel activation

1. Ka and Kdr channels first open

2. Kbk channels open

3/ other known and unknown K channels open

29

large number of ion channel genes create neurons with diverse ___

electrical properties

30

fast AHP occurs in ___ seconds

2-5 ms

31

 medium AHP occurs in ___ seconds

10-100 ms

32

slow AHP occurs in ___ seconds

100-3000 ms

33

inactivation pattern of Kv2.1 channels?

show little inactivation

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34

inactivation pattern of Kv4.1 channels?

inactivate rapdily after depolarization

35

when do inward rectifers allow more current flow?

during hyperpolarization

36

why do so many genes encode K+ channels?

activation, gating, inactivation

37

shape complex electrical responses influence 

1. duration of AP

2. resting membrane potential 

38

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

increasedintracellularCa++ and sometimes to membrane depolarization.

39

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

diversity

40

what do channelpathies result from?

they happen due to mutations in channel genes

41

channelpathies in voltage gated Ca channels 

congential stationary night blindness

familial hemiplegic migraine

episodic ataxia type 2

42

channelpathies in Na channels

generalized epilepsy with febrile seizures

43

channelpathies in K channels

benign familial neonatal convulsion 

44

channelpathy that causes congential stationary night blindness

Ca

45

channelpathy that causes generalized epilepsy with febrile seizures

na

46

channelpathy that causes familial hemiplegic migraine

Ca channel

47

channelpathy that causes benign familial neonatal convulsion

K

48

what toxins block Na channels?

ttx and saxitoxin

49

what toxins inactivate Na channels?

Batrachotoxin (frogs)

50

what does a-toxin do?

prolongs the duration of Na channels

51

what does b-toxins do?

shift voltage activation of Na channels

52

which toxins blod K channels?

apaminin (bees) and dendrotoxin (wasps)

53

what does TEA block?

K channels and AcH receptors

54

What blocks Ca channels? 

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

55

active ion transports work ___ a electrochemical gradient

against

56

how do active ion transporters and channels differ?

active ion transporters having slow binding and unbinding

also are slower transport than channels

57

w-conotoxins blocks ___ channels

n type Ca

58

w-agatoxin blocks ___ channels

P/Q type Ca channels

59

____ form a compelx with the ion they transport

active ion transporters

60

how do ion exchangers work?

they don't use energy

but trade an intracellular ion for an extracellular one

61

how do ion co-transporters work?

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

62

methods in determining channel type?

1. patch clamp technique

2. gene cloning

3. x ray crsytallography