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Flashcards in Intro to CNS Deck (55)
1

Biological membranes are essentially impermeable to ions

This is because the internal region of the bilayer is very hydrophobic and ions are hydrated by water

2

Protein families have evolved that function to allow ionic passage across the membrane

1. ATPase driven pumps
2. Transporters
3. Ion channels: some generalities

3

a) Integral membrane proteins
b) Multiple membrane-spanning domains
c) Form a hydrophobic channel in the center

ion channels

4

Selective for ions and regulated by :

changes in the cellular environment

5

Ion Channels have______gene products; multiple subunits and are Glycosylated on the

Multiple
extracellular side

6

Ion Channels have Consensus sequences for

kinases

7

non-gated, always open

Passive:

8

gated; the closed and open states of the channel are regulated

Active

9

Gating mechanisms

Membrane potential differences
small extracellular molecules (NT)
membrane proteins
intracellular molecules

10

this type of ion channel is open at RMP and can be either active or passive

leak chanel

11

all passive channels are

leak channels

12

intracellular proteins are predominately

anions

13

leak channels in the plasma membrane allow _____ and _____ movement across the membrane

K+ and Cl-

14

Conductance of _____ is 20 times greater then to Na

K+

15

Due to unequal conduction potentials, we see ______ distribution of Cl, K and Na across the membrane

unequal

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____ is high inside and low outside

K+

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____ and ____ are high inside and low outside

Na and Cl

18

We have both ____ and ______ for Na, Cl and K across the membrane

chemical and electrical potential

19

Ena =

+55mV

20

Ek =

-75 mV

21

Ecl=

-69mV

22

Some of the leak is opposed by the NaK ATPase pump that moves _____ions out of the cell and ____ions into the cel

Na
K

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ion channels for a ______ channel in the center

hydrophyilic

24

is the membrane potential at which an ion is in electrochemical equilibrium across membrane

Nerst potential

25

As we increase conductance to Na we start to depolarize the membrane which leads to

voltage gate Na channels opening

26

These are more gradual opening and slower inactivation

Voltage gated K+ channels

27

Action potentials are

all or none; get to 100 mV in amplitude in 1-10 msec

28

Action potential is propagated down the axon through

cycles of depolarization and repolarization

29

Mechanisms by which initial change in membrane potential occurs to begin an action potential

Synaptic potential

30

Synaptic potential have what type of change in membrane potential

graded, short and small
the are LOCAL
and able to summate

31

graded, short and small
the are LOCAL
and able to summate

Synpatic potential

32

Two types of synaptic potentials

EPSP and IPSP

33

membrane potential becomes more positive; if it increases enough, threshold will be reached

Excitatory, postynaptic potential

34

EPSP can occur by increased conductane of

Na or Cl bc both push for depolarization
-- such as Nicotinic chlinergic R or Glutamate receptor

35

EPSP can occur by decreased conductance of

closing a channel that is open at resting membrane potential; these are slower onset changes that last longer

36

closing a channel that is open at resting membrane potential; these are slower onset changes that last longer

example of EPSP via decreased conductance

37

Example of decreaed conductance causing EPSP

Closing a leak channel for K+
see changes in phosphorylation of the channel or regulated by second messenger cascades such as GCPR

38

Ligand gated chloride channel such as a GABA R is an excample of

IPSP
a) Increased conductance of the membrane to either potassium or chloride

39

Following are examples of what:
(a) Via direct interactions between the channel protein and G protein
(b) As a result of changes in phosphorylation state of closed K channels (mediated by second messenger cascades)

G protein coupled receptor activation can result in the opening of K channels
causes IPSP

40

G protein coupled receptor activation can result in the opening of K channels in two ways

through direct interactiosn btwn G protein and K+ channel
as a result of change in phosyphorylation state of K channels that are closed

41

Resting potential relies of
Channel specificity:

Channel specificity: non gagted K and Cl- channels; some nongated Na

42

Gating mechanism for resting potential

none

43

Properties of Resting potential

Usualy steady from -35 to -70 mV

44

Action potential channel specificity:

Independently gated Na and K channels

45

Gating mechanism for Action Potential channels

voltage gated

46

Properties of Action potential

all or none, 100 mV in amplitude; 1-10 msec in duration

47

Increased conductance EPSP channel specificity:

non-volatge gated channels; nonselective for univalent cations

48

Incrased conductance EPSP gating mechanism

chemical with extracellular site binding

49

Properties of increased conductance EPSP channels

graded, fast, several msec in duration and several mV in amplitude

50

Increased conductance IPSP channel specificity

non-voltage gated chans for K+ or Cl-

51

Gating mech for increased IPSP

Chemical with extracell binding site

52

Properties of increased conductance IPSP

graded, fast, severeal msec in duration and several mV in amplitude

53

Decreased EPSP channel specificity

Potassium leak channesl

54

Decreased EPSP gating mechanism

Chemical: GPCR then 2nd messenger

55

Properties of decreased EPSP

graded, fast, several msec in duration and several mV in amplitude