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Flashcards in Lecture 2 Deck (139):
1

Another name for the specific electrical potential (voltage) created by ions in and out of a cell:

Nernst or equilibrium potential for the ion

2

T or F? Opening K+ channels will depolarize the cell.

F. Hyperpolarize

3

Will opening the Na+ channels depolarize or hyper polarize the cell?

depolarize

4

When is there a driving force on the ion to move it in or out of the cell?

When the cell voltage is not the same as the ion's Nernst potential

5

Another name for Nernst potential:

equilibrium potential

6

What factors influence the MP of the cell?

driving force coupled with the ion's channel conductance

7

How are the opening and closing of channels regulated?

voltage-gated, ligand-gated, or other factors

8

Voltage-gated cells rely on:

membrane potential

9

ligand-gated channels rely on:

chemicals and neurotransmitters

10

What creates the negative charge inside the cell?

K+ leaving (he also said the Na-K pump contributes little tot the inside negative charge)

11

What two forces act on ions?

charge and concentration

12

T or F? At equilibrium there is no flow of ions across the membrane.

F. no NET flow

13

When is equilibrium reached?

chem force is equal and opposite in direction to the electrical force on the ion

14

T or F? When a neuron is at resting potential the Na ions are at equilibrium.

F

15

T or F? When a neuron is at resting potential the K ions are at equilibrium.

F.

16

T or F? Charged molecules are not subject to a diffusive chemical driving force.

F. applies to all charged and uncharged molecules

17

T or F? Uncharged molecules are not subject to as electrical driving force.

T.

18

Another way of saying chemical gradient:

Concentration gradient

19

What is the diffusion of a specific ion across the PM governed by?

driving force + # of open channels

20

Is the Na conc high or low inside a typical nerve cell at rest?

low

21

In which direction do both the chemical and electrical forces go with a typical nerve cell at rest for Na?

into the cell

22

In which direction do the chemical and electrical forces go with a typical nerve cell at rest for Cl-?

the chemical driving force is directed inside the cell and the electrical driving force is directed outside the cell

23

In which direction do the chemical and electrical forces go with a typical nerve cell at rest for K?

the chemical driving force is directed outside the cell and the electrical diving force is directed inside the cell

24

With which molecule are the 2 driving forces complimentary, Na, K, or Cl-?

Na+

25

With which molecule are the 2 driving forces offset completely, Na, K, or Cl-?

Cl-

26

With which molecule are the 2 driving forces offset incompletely, Na, K, or Cl-?

K+

27

T or F? If the concentration gradient for an ion is know, the electrical gradient (voltage) can be calculated.

T. With Nernst Eq.

28

Is the electrical gradient typically the same as the membrane potential for the cell?

No, only if this is the only permeable ion

29

In which situation would the electrical gradient be the same as the membrane potential for the cell?

if this is the only permeable ion

30

Eq. Pot for each ion Nernst eq:

V = (61/n)Xlog(Cout/Cin) (of a given ion) n = ion valence, c = concentration

31

Nernst potential for Na+ =

+60mV

32

Nernst potential for Cl- =

-63mV

33

Nernst potential for K+ =

-90mV

34

When the membrane conductance increases for a particular ion,:

the membrane potential will move toward the Nernst potential for that ion

35

In which direction will K+ flow if the cell is at -70mV inside?

out of the cell to try and reach its Nernst potential of -90mV

36

What are the "n" values for K+, Na+, and Cl-?

+1, +1, and -1

37

Ion conc.'s in and out of the cell for K+ at equilibrium:

5mM out, 150 mM in

38

Ion conc.'s in and out of the cell for Na+ at equilibrium:

145mM out, 15 mM in

39

Ion conc.'s in and out of the cell for Cl- at equilibrium:

108mM out, 10 mM in

40

Ion conc.'s in and out of the cell for Ca++ at equilibrium:

1 mM out, 0.0001 mM in

41

In which direction will Na+ flow (in or out) for a neuron resting at -60mV?

in to reach it's Nernst potential of +60mV

42

In which direction will Cl- flow (in or out) for a neuron resting at -60mV?

in (very little) to reach it's Nernst potential of -63mV

43

In which direction will K+ flow (in or out) for a neuron resting at -60mV?

out to reach it's Nernst potential of -90mV

44

What is the driving force for K+ in a cell at -90mV?

zero bc that is the Nernst potential for K+, the cell is at equilibrium

45

What factors determine the total current produced by a given ion?

driving force and conductance

46

Equation for current produced by an ion:

conductance X driving force (Vm-Veq)

47

math symbol for conductance:

g

48

math symbol for current flow of an ion:

I

49

T or F? Driving force = Veq - Vm.

F. = Vm - Veq

50

What is the driving force of K at a RMP of 70mV? Ek = -92mV

-70 - (-92) = +22

51

2 meanings of conductance:

1. conductance of a single channel
2. Cell conductance due to opening of a population of channels

52

How many channels and how wide the channels are:

conductance

53

T or F? For a cell at rest, there are few Na+ channels open and many K+ channels open

T

54

Will a cell have a positive or negative charge if the g(Na) > g(K)?

positive because the conductance for Na+ is greater

55

Will a cell have a positive or negative charge if the g(Na)

negative bc the conductance for K is greater

56

Will K flow in or out of a cell if the conductance of K is greater than Na?

out

57

Will Na flow in or out of a cell if the conductance of K is greater than Na?

in

58

Will K flow in or out of a cell if the conductance of Na is greater than K?

out

59

Will Na flow in or out of a cell if the conductance of Na is greater than K?

in

60

relative influence of sodium channels is:

gNa/(gNa + gK)

61

relative influence of potassium channels is:

gK/ (gNa + gK)

62

What channels do you want to open and which do you want to close in order for a cell to depolarize:

Open Na+ and close K+

63

This ratio controls the MP?

conductance ratio

64

Is GABA an inhibitory or excitatory neurotransmitter?

inhibitory

65

Is glycine inhibitory or excitatory?

inhibitory

66

What effect, if any, will GABA and glycine (separate questions) have on channels?

they both open chloride channels, inhibitin depolarization (- charge enters the cell)

67

Will opened Cl- channel depolarize or hyperpolarize a cell?

hyperpolarize

68

Why won't a cell depolarize when the Na channels are opened after Cl- channels are opened?

Cl- reenters the cell, preventing depolarization

69

Which has a higher conductance, Cl or Na?

Cl

70

Which has a higher conductance, Cl or K?

Cl

71

The opening of Cl- channels will ____ the responsiveness to Na channels.

shunt

72

The MP of a cell is determined by:

the permeability of each ion (P) and the eq pot. of each ion

73

Can ions flow against their electrochemical gradient in facilitated diffusion?

No

74

Which transport ions faster, channels or carriers?

channels

75

Ions pass through channels based on:

size and charge

76

T or F? Some channels are very selective while allowing a LOT of that specific molecule to pass

T

77

T or F? Specificity of channels for ions with the same charge is absolutely specific.

F. ranges from highly specific to relatively non specific

78

T or F? Cation and anion channels are absolutely specific for charge.

T

79

T or F? Ligand-gated channels are voltage-sensitive

F

80

How many times do voltage gated channels span the bilayer?

6-transmembrane

81

How many domains does a Na channel have?

4

82

What type of segments does a Na channel have?

6TM

83

T or F? The tranmembrane segments of the channels are always helices.

F. usually

84

Which of the 6 segments has a charge on it for voltage sensitive channels?

4th

85

Do the voltage sensitive channels open when the voltage changes inside or outside the cell.

inside (only?)

86

Which segement of the channel can move in the membrane and create a pore in the membrane?

5th and 6th

87

When in the channel is the p loop found?

bw the S5 and S6

88

T or F? the p loop is a protein

T

89

Which segments form the gate for the channel?

S5 and S6

90

This type of channel has one 6-TM peptide:

K channel

91

How many subunits combine to form the K channel?

4

92

What structure determines what ions can pass through the channel?

p loop (a protein)

93

Examples of 6-transmembrane channels:

K+, HCN, cyclic nucleotide (CNG), PKD, TRP, voltage gated Na and Ca channels, polycystic kidney disease (?)

94

HCN channels are regulated by:

cAMP

95

CNG channels are regulated by:

cGMP or cAMP

96

How many segments are require to form the CNG channels?

4, 6-transmembrane proteins

97

What are CNG channels involve in?

vision and olfaction

98

What are TRP channels sensitive to?

pH, temp, menthol, capsaicin (hot pepper), sweet bitter and umami taste buds, etc.

99

Channels both start and end on the (intra/extra) cellular side of the cell

intra

100

What does ENaC stand for?

epithelial Na Channel

101

How many subunits is ENaC made of and name?

3 (alpha, beta, gamma)

102

How many transmembrane segments does each subunit of the ENaC have?

2 and a large extracellular loop

103

What is required for the ENaC to open?

nothing. constitutively open

104

What is ENaC involved in?

salt taste in tongue and salt excretion in kidney

105

2 types of ligand receptors:

Ionotropic and Metabotropic

106

This type of ligand activated receptor binds the ligand and rapidly activates channel:

Ionotropic

107

This type of ligand activated receptor binds the ligand and slowly activates channel:

Metabotropic

108

The channel is part of the receptor in this type of ligand activated receptor:

ionotropic receptor

109

2 excitatory ligands:

glutamate and AcH

110

2 inhibitory ligands:

GABA and Glycine

111

What affect does AcH have on the heart?

slows heart

112

What type of receptor does AcH use?

G-protein receptor

113

These are G-protein coupled receptors:

metabotropic

114

The G-protein may lead indirectly to:

channel activation or modulation

115

enhance or suppress channel activity:

modulation

116

most modulators are:

neurotransmitters

117

What type of channel is the AcH receptor?

ligand-gated channel

118

What subunits is the AcH receptor made of?

2 alpha, 1 beta, 1 delta (check)

119

This is a ligand-gated receptor family

Ionotropic AcH, GABA, and Glycine receptors

120

How many subunits are the Ionotropic AcH, GABA, and Glycine receptors made of?

5 subunits

121

How many times do the Ionotropic AcH, GABA, and Glycine receptors cross the membrane?

4 times

122

What forms the pore of the Ionotropic AcH, GABA, and Glycine receptor?

M2

123

How many times does each subunit of the inotropic glutamate receptor cross the membrane?

3 times, 2nd loop comes back and doesn't cross all the way

124

How many subunits form the inotropic glutamate receptor?

4

125

3 different types of Glutamate Receptors:

AMPA, NMDA, Kainate

126

how many channels does the GPCR form?

zero

127

How many transmembrane proteins does the GPCR have?

7

128

How is the GPCR activated?

ligand activated

129

What does the GPCR activate inside the cell?

G-protein

130

What does the GPCR start?

2nd messenger cascade

131

This type of receptor often regulates a channel:

GPCR

132

T or F? The GPCR amplifies response to a stimulus.

T

133

How many subunits is the GPCR made of?

3

134

The binding of one ligand to a GPCR can lead to the release of _____ of molecules on the other side of the membrane.

1000's

135

T or F? ATP is required for stimulation of the GPCR.

F. GTP

136

Examples of GPCR's:

sweet taste receptors, bitter taste receptors, umami taste receptors, neurotransmitter receptors

137

These receptors are involved in autoreceptro feedback:

ionotropic and metabotropic receptors

138

What affect will glutamate have on a metabotropic receptor?

suppression of voltage-gated calcium channels, negative feedback that controls transmitter release

139

What affect will glutamate have on a ionotropic receptor?

depolarize synaptic cell