Lecture 1: Synaptic Transmission and Plasticity Flashcards Preview

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Flashcards in Lecture 1: Synaptic Transmission and Plasticity Deck (111):
1

AP is generated ______ of presynaptic neurons, and propagates down to the axon terminal.

At the axon hillock

2

VGCC

Voltage-gated calcium channel

3

What type of receptors are located on the end-plate of a muscle cell?

nAChR (ionotropic receptors)

4

iGluR

Ionotropic glutamate receptor

5

What occurs when ACh binds to the nAChR at the end-plate?

Na+ and Ca++ fluxes into the muscle cell, generating a postsynaptic EPSP.

6

What occurs in a muscle cell when the integrated EPSP of the postsynaptic cell reaches threshold?

Voltage-gated Na+ opens, and an AP is generated.

7

The brain functions as a _________, primarily connected via ________, and sometimes ________.

Neural cell network; chemical synapses; electrical synapses

8

In the cortex (hippocampus), a pyramidal neuron forms ________ synapses. The adult brain contains ___-___ ________ synapses.

Several thousand; 100-500 trillion

9

Postsynaptic neurons integrate synaptic inputs (+/-) by spatial and temporal summation into a ________ code. This code is transmitted to innervated cells.

Signal

10

How does the location of axon C alter the depolarization of the dendrites of the pyramidal neuron?

Q image thumb

Depolarization is smaller, and occurs later because it diminishes over time.

A image thumb
11

2 most common neurotransmitters:

1.
2.

1. Glutamate
2. GABA

12

Dendritic spines are small, ________ of dendrite

Membranous protrusions

13

How do electrical and chemical synapses differ in their directionality?

Electrical: bidirectional
Chemical: unidirectional

14

In chemical neurotransmission, pre- and postsynaptic compartments are ________ in ________ and ________.

Asymmetrical; molecular structure; function

15

GABAergic synapses are likely to occur ________, while glutamatergic synapses are likely to occur ________ (location).

Dendritic trunk; dendritic spine

16

The important presynaptic neurotransmission structure is ________, while the postsynaptic neurotransmission structure is ________.

Active zone; post-synaptic density

17

Neurons function as "computational devices", becauses synapses not only ________ information, but also ________ the AP-coded information.

Transmit; transform

18

AP potential pattern in AP burst neurons vs. "tonic" AP neurons:

A image thumb
19

Burst and tonic neurons allow for neurons to act as ________ by transmitting and transforming AP-coded information.

Computational device

20

Pre- and postsynaptic neurons transmit and transform coded information via ________.

Specific subcellular structures (i.e. receptors).

21

2 types of presynaptic structures:

1.
2.

1. Axon terminal
2. Terminal bouton

22

T/F: it is impossible for a neuron to be able to release multiple NTs

F

23

The main function of the active zone is to ________.

Transform presynaptic APs into NT release.

24

NT release occurs via the machinery of ________.

Exocytosis

25

Active zones are composed of ________ containing core constituents, such as...

An evolutionarily conserved protein complex; VGCC, t-SNARE, RIM, Munc13. RIM-BP, etc.

26

4 principle functions of the active zone in NT release:

1.
2.
3.
4.

1. Docking and priming vesicles

2. Anchoring VGCC proteins to the presynaptic membrane, enabling Ca++-mediated fast excitation/release coupling 

3. Localizing/anchoring presynaptic proteins and making them exactly opposite the postsynaptic density, via trans-synaptic cell-adhesion proteins

4. Mediating short/long-term presynaptic plasticity

27

How does the active zone mediate presynaptic plasticity?

Either directly by responding to second messengers (i.e. Ca++) or indirectly by recruiting other proteins such as GPCRs that are responsible for plasticity.

28

How does a presynaptic terminal differ from a terminal bouton?

Presynaptic terminal: an enlargement that contains vesicles that store neurotransmitter at the end of an axon.

Terminal bouton : different segments of a single axon can be enlarged and form synapses (and then continue). 

A image thumb
29

The synaptic cleft = ____ nm in width.

20 nm

30

The general name for proteins that align the AZ directly with the PSD is ________.

Synaptic adhesion proteins

31

2 synaptic adhesion proteins: ________ and ________.

Neurexin and neuroligin

32

The presynaptic synaptic adhesion protein is ________, while the postsynaptic adhesion protein is ________.

Neurexin; neuroligin

33

The postsynaptic density consists of:

1.

2.

3.

1. NT receptors and ion channels

2. Scaffold proteins

3. Signaling proteins

34

The postsynaptic density lies adjacent to ______ of the postsynaptic membrane, in close apposition to the presynaptic AZ.

The cytoplasmic face 

35

Neurexin and neuroligin are both ______ proteins.

Transmembrane, synaptic adhesion

36

In the early 1960s, glutamate was initially discovered as _______.

A NT in insects.

***It was not even known that it was one of the 20 amino acids.

37

In the 1980s, glutamate was recognized as ______.

The primary excitatory NT in the CNS of mammals.

38

What types of cells can produce glutamate?

ALL cells that can undergo the tricarboxylic acid cycle (TCA) AKA all cells that can metabolize glucose.

39

TCA is also known as _____.

Citric acid cycle

40

Glutamate can be converted to glutamine by ________.

Glutamine synthetase

41

Glutamine can be converted to glutamate by ________.

Glutaminase

42

How do glutamine and glutamate differ?

By an amino group. Glutamaine has an extra NH3.

43

How is GABA formed?

From glutamate!

44

Enzyme that converts glutamate to GABA: _____.

GAD: glutamic acid decarboxylase

45

Protein that packs glutamate into presynaptic vesicles: ____.

vGluTs

46

vGluT stands for: _____.

Vesicular glutamate transporters

47

How many types of vGluTs are there? What are the implications of this?

3 types, vGluT1-3. 

Each can be expressed in specific glutamatergic terminals, and therefore you can use them to identify specific brain projections and synapses.

48

vGluT activity is _______-dependent.

Proton (H+). The synaptic vesicles are more acidic than cytosol.

49

What is more acidic: the synaptic vesicles, or the cytoplasm of the neuron?

Synaptic vesicles

50

How does vGluT get the energy to pump glutamate into the vesicle?

The v-ATPase pumps H+ against its concentration gradient, vGluT then uses this gradient as an antiporter, by transporting 1 glutamate into the vesicle, and 1 H+ out of the vesicle.

51

Three pools of synaptic vesicles:

1.
2.
3.

1. Readily releasable pool
2. Reserve/recycling pool
3. Resting pool

52

_____ AKA recycling pool

Reserve

53

_____ AKA spontaneous release pool

Resting pool

54

Readily releasable pool

Vesicles are already docked at the active zone, and densely packed with NTs.

55

Reserve/recycling pool

Not docked at active zone, but densely packed with NT, and can dock at active zone to become a readily releasable pool.

56

Resting pool

An empty vesicle, that will eventually fill with glutamate via vGluT.

57

______ is critical for the regulation of synaptic plasticity and homeostasis.

Spontaneous neurotransmitter release.

58

Calcium entry through the VGCC triggers the ______ (______) of vesicles docked on active zones.

Exocytosis (membrane fusion)

59

How is the fused vesicular membrane retrieved to form more synaptic vesicles?

Endocytosis

60

NSF protein is ______ (type of protein).

An ATPase

61

SNAP stands for ______.

Soluble NSF Attachment Protein

62

SNARE stands for ______.

SNAP Receptor

63

SNAREs are _____ proteins.

Transmembrane

64

Synaptotagmin is a _____ protein, that functions as a _____.

Transmembrane protein; Ca++ sensor

65

The _______ pool is especially important for synaptic plasticity and homeostasis.

Resting

66

SNAP binds to ____ and ____.

v-SNARE and t-SNARE, causing the vesicle to fuse with the plasma membrane.

67

The binding of calcium to ______, triggers the assembly of ______ and ______.

Synaptotagmin; t-SNARE; vSNARE

68

Where is t-SNARE located?

In the presynaptic membrane of the active zone

69

The SNARE complex (v-SNARE + t-SNARE) recruits ______ and ______ to form a membrane fusion complex.

Cytosolic SNAP and NSF

70

The membrane fusion complex consists of:

1.

2.

3.

4.

1. v-SNARE

2. t-SNARE

3. SNAP

4. NSF

71

What occurs when NSF hydrolizes ATP?

1.

2.

3.

1. SNARE complex disassembles

2. Plasma membrane fusion

3. Release of NT

72

Two ways by which NT molecules are removed from the synapse: ______ and ______

Taken-up, broken down

73

Which cell types can take up NTs?

1.

2.

3.

1. Presynaptic neurons

2. Postsynaptic neurons

3. Glial cells

74

_____ are transporters that take up glutamate.

EAATs: excitatory amino acid transporters

75

The ______ and the ______ of EAATs critically regulate the _______.

Subcellular localization; activity level; kinetics of glutamatergic synaptic response (EPSPs/EPSCs).

76

Where are EAAT1 and EAAT2 primarily located?

In membranes of glial cells (astrocytes and oligodendrocytes)

 

77

EAAT2 is mainly located _____.

In astrocytes

78

What is the major route of taking extracellular glutamate up into cells for reuse?

EAAT2, located in astrocytes

79

______ is the EAAT expressed in neurons.

EAAT3 and 4

80

_____ is the major EAAT expressed in the retina.

EAAT5. It is localized to photoreceptors and bipolar neurons

81

EAAT1 is known as GLAST in rodents, this is known as a ______.

Ortholog

82

In rodents, the ortholog of EAAT1 is _____.

GLAST

83

In rodents, the ortholog of EAAT2 is _____.

GLT-1

84

In rodents, the ortholog of EAAT3 is _____.

EAAC1

85

What actually are EAATs?

Membrane-bound pumps ionic pumps that resemble ion channels

86

Where do EAATs and get their energy from to pump glutamate into the cell?

From the cotransport of ions moving down their concentration gradients. The maintenance of these gradients DOES require ATP though.

87

What ion cotransport is required for glutamate to be taken up into a cell by EAAT2?

1 K+ is pumped out

3 Na+ and 1 H+ are pumped in

88

At physiological pH, glutamate's charge is _____.

Negative

89

Which EAAT is essential for glutamate homeostasis in the brain?

EAAT2

90

Glutamate concentration in the extracellular space:

0.001 mM (or 1 µm)

91

Glutamate concentration in neurons:

10 mM

92

Glutamate concentration in glial cell processes:

0.5 mM

93

Glutamate concentration in synaptic vesicles:

100 mM

94

EAAT2 is highly expressed by _______ in _______ regions in the brain.

Astrocyte; most regions in the brain

95

Under resting conditions, the concentration of glutamate in the extracellular space is ____. After an AP, the concentration of glutamate may reach ____.

0.001 mM, 1-5 mM

96

Which glial cell takes up the majority of glutamate?

Astrocytes (via EAAT2)

97

% of glutamate taken up into astrocytes

90

98

EAAT1/GLAST is high in _______.

Cerebellar Burgmann cells

99

What occurs to glutamate in astrocytes?

It is converted to glutamine via  glutamine synthetase.

100

What enzyme converts glutamate to glutamine?

Glutamine synthetase

101

What enzyme converts glutamine to glutamate?

Glutaminase

102

If astrocytes take up the majority of glutamate, how does it get back into the presynaptic neuron?

Glutamate is converted to glutamine in astrocytes (by glutamine synthetase).

Glutamine is released from the astrocytes, and transported back into the neuron by glutamine transporter (GLNT).

103

_____ transports glutamine from astrocytes to the presynaptic neuron.

Glutamine transporter (GLNT)

104

Where is glutamine synthetase found?

Astrocytes

105

Where is glutaminase found?

Presynaptic neurons

106

How is glutamate transported from the cytosol into synaptic vesicles?

vGluTs

107

_______ critically regulates the glutamate-glutamine cycle.

Neuronal activities

108

The process of astrocytes taking up glutamate to the time when it is taken back up into synaptic vesicles in the presynaptic neuron is known as:

The glutamate-glutamine cycle

109

The glutamate-glutamine cycle is part of _______.

Synaptic transmission

 

110

Where is GLNT (glutamine transporter) located?

On the membrane of presynaptic neurons

111