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Flashcards in Channels and Transporters Lec04 Deck (62)
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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)

6

what are macroscopic currents due to?

current flow through may channels

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 

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)

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

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