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Flashcards in Synaptic transmission Deck (133):
1

What are the two types of synapses?

Electrical
Chemical

2

What are the two types of chemical synapses?

Neuron-neuron
Neuron-muscle

3

Electrical synapses are made up of what membrane proteins? Where are these from (which cells)?

Connexons--one from each neuron participating in the synapse

4

How many connexins make a connexon?

6

5

Are most electrical synapses uni or bidirectional?

Bidirectional

6

How fast are electrical synapses?

Extremely fast

7

Why do electrical synapses have a low selectivity?

Connexons allow water and ions to pass through without any specific selection (size is only selection)

8

How do electrical synapses relate to chemical synapses?

They mediate chemical synapses

9

What are the four ways that neurons can transmit chemical signals?

1. Endocrine
2. Paracrine
3. Synaptic
4. Autocrine

10

What is autocrine signalling for neurons?

Receptors on pre-synaptic cell for transmitter it releases

11

What is a neuromodulator?

chemical messenger that can affect release of neurotransmitter or the receptor function of a neurotransmitter. Some chemicals can be both neurotransmitters and neuromodulators.

12

What is paracrine signalling?

Signals released to local cells

13

What organelle is always found in presynaptic synapses?

Mitochondria b/c there is a high energy need

14

Are neurotransmitters in presynaptic neurons made on the spot or are they stored?

Stored in vesicles

15

The influx of what ion leads to release of the neurotransmitters in vesicles?

Ca

16

What are the transmembrane proteins that hold chemcial synapses togehter?

Neurexins

17

Are chemical synapses unidirectional, or bidirectional?

Unidirectional

18

True or false: in influx of Ca ions in the presynaptic bouton causes a moderate-major change in [Ca]

False-very small and localized

19

The increase in [Ca] in the presynaptic bouton causes what to happen?

Release of neurotransmitters

20

True or false: the neurotransmitter that is released from the presynaptic bouton always causes channels in the postsynaptic cleft to open

False--can open or close

21

What are the steps in the recovery phase of a chemical synapse? (3)

1. Repolarization of presyapse via K= efflux
2. Ca channels close
3. Ca removed from cleft

22

What are the roles of SNARE proteins in synaptic transmission? (2)

Form a complex between the vesicle and the presynaptic cell membrane

Sensors of Ca

23

How is Ca removed from its localized position in the presynaptic neuron? (4)

1. Diffusion
2. Ca binding proteins
3. Transported into internal Ca stores
4. Pumped out

24

How are the vesicles recycled in presynaptic membranes?

Through clatharin mediated endocytosis

25

Why is it possible to deplete chemical neurons?

It takes 1 minute to replenish vesicles

26

What are the three major small-molecule neurotransmitters?

Amino acids
Acetylcholine
Amines

27

What are the two different type of amines that are neurotransmitters?

Monoamines
Catecholamines

28

What are the two responses to neurotransmitter binding on the postsynaptic bouton? What are the two processes that can take place?

excitation or inhibition

Depolarization or chemical cascade

29

What are ionotropic receptors?

Ligand gated ion channels on the postsynaptic membrane

30

What are metabotropic receptors?

G-protein coupled receptors

31

Are metabotropic receptors faster or slower acting than ionotropic receptors?

Slower

32

True or false: A postsynaptic neuron can have receptors for more than one kind of neurotransmitter

True

33

The major excitatory neurotransmitter in the brain and spinal cord is of what type?

Glutamate

34

What is the pore that glutamate opens? Which way do ions flow?

Na/K pore, which lets some K out, but a lot of Na in

35

What happens to the postsynaptic neuron when glutamate binds to its channel (depolarization or hyperpolarization)?

Depolarization (d/t net influx of Na) and thus excitation

36

What does it mean that the depolarization caused by a single glutamate receptor is decremental?

It is only local, and will not elicit a depolarization event by itself

37

What is the primary inhibitory neurotransmitter in the nervous system?

GABA

38

True or false: Metabotropic receptors can cause excitatory effects in several ways

True

39

Ionotropic GABA receptors are permeable to what ion? What happens when these open?

Cl-

This causes CL to flow down its [C] gradient into the neuron, and hyperpolarize it

40

 If ECl- is more negative than resting membrane potential, which is the case for most neurons, then increasing Cl- permeability causes Cl- to flow where?

Into the cell

41

What would happen to a postsynaptic neuron if a metabotropic receptor caused K channels to open (and a subsequent efflux of K)?

Hyperpolarization

42

How can metabotropic receptors effect a depolarization through K or Cl channels?

Decrease the permeability of the channels

43

What is a synaptic delay?

Time interval between when action potential invades the pre-synaptic terminal and when a membrane potential change begins in the post-synaptic cell

44

Which type of synapse has a longer delay: chemical or electrical?

Chemical

45

What are the three ways in which transmitters are removed from the synaptic cleft?

Diffusion
Enzymatic degradation
Reuptake/transport

46

What is the MOA of cocaine?

Binds to the dopamine reuptake protein ono the presynaptic neuron, and prevents reuptake

47

What is the target of SSRIs?

5HT transporters

48

What is the target of MAOIs?

Monoamine oxidase (the enzyme that oxidizes 5HT

49

What is the target of TCA (tricyclic antidepressants)

5HT transporter

50

What is temporal summation?

When the same presynaptic neuron gives a signal in rapid succession to elicit a response in the postsynaptic neuron

51

What is spatial summation?

When two or more separate neurons create signals that are given together to elicit a postsynaptic response

52

What is synaptic efficacy?

how big an effect a synapse has on the postsynaptic cell.

53

What is synaptic plasticity?

"the ability of synapses to strengthen or weaken over time, in response to increases or decreases in their activity" - wiki

54

What is a neuromuscular junction?

A specialized synapse between a motoneuron and a muscle fiber

55

Where does the mylein sheath end in a neuronmuscular juncation?

Just before the synaptic bouton

56

What is the major difference in neuromuscluar junction presynapses, as compared to CNS synapses?

There are multiple active zones within the presynaptic terminal

57

What organelle is found in high amounts in the presynaptic terminal of a neuromuscular junction?

Mito

58

What is the major difference in neuromuscluar junction postynapses, as compared to CNS synapses? What is the purpose of this?

There are many junctional folds

59

What is the only neurotransmitter found in neuromuscular junctions? Receptor?

Acetylcholine and its nicotinic receptor

60

What is the MOA of nicotinic acetylcholine receptors?

Allows for the influx of Na (and smaller efflux of K), activating Na channels elsewhere

61

How is acetylcholine degraded?

Acetylcholine esterases

62

What is the end plate depolarization?

The depolarization that takes place in neuromuscular junctions

63

What is the function of anticholinesterases?

Inhibit acetylcholine esterase, and prolong the EPP

64

Why are neuromuscluar junctions considered "safe and reliable"?

since in a normal, healthy person an action potential in the motor neuron always causes an action potential in the skeletal muscle fibers it synapses on

65

Why is reuptake of choline essential for motor neurons?

This is necessary since motor neurons cannot synthesize choline and choline does not pass through cell membranes easily.

66

What type of receptor is the nicotinic acetylcholine receptor? What are the ions that this uses, and how?

Ligand gated channel (ionotropic).

Increases permeability of K and Na, but more so to Na

67

What type of channel is used in the reuptake of acetylcholine?

Secondary active synporter (with Na as the opposing ion)

68

How many motor neurons innervate a skeletal muscle?

One, and only one

69

Are there inhibitory synapses at neuromuscular junctions?

No--ONLY excitatory

70

When you talk about inhibiting a skeletal muscle cell this means what?

that the alpha motor neuron innervating that cell is inhibited.

71

Why do neuromuscular junctions need to ensure that the signal they send is strong (which they do via multiple terminals, multiple active zones, etc.)?

Becauses there is a 1-1 ratio of motor neurons to muscle fibers

72

What is the MOA of botulina toxins? What are the symptoms of botulina poisoning?

Proteinase that cleaves the SNARE complex associated with vesicles in the presynaptic neuron. Thus vesicles will not be held near the end of the synapse

Symptom = flaccid paralysis

73

What is the MOA of tetanus?

Cleaves the SNARE protein of glycine neurotransmitters (interneurons) of neurons in the spinal cord

74

What is Eaton-Lambert syndrome?

An autoimmune attack on voltage – gated Ca++ channels in the terminals of somatic motor nerves. This inhibits vesicle release

75

What is the MOA of myasthenia gravis?

autoimmune disease which reduces the number of acetylcholine receptors at the postsynaptic neuromuscular junction

76

What is the autoimmune disease discussed in lecture that affects presynaptic channels?

Eaton-Lambert syndrome

77

What is the autoimmune disease discussed in class that affects postsynaptic channels?

Myasthenia gravis

78

What is the MOA of neostigmine in treating myasthenia gravis?

Reversibly inhibits acetylcholine esterase

79

Where does the muscle weakness of Myasthenia gravis usually appear?

In the face

80

What are the signs/symptoms of myasthenia gravis?

Muscle weakness, especially if it gets worse in the day.

Neck weakness against physician's force

81

What is the MOA of nicotine?

Agonist of the nicotinic acetylcholine receptors

82

What is the MOA of bungaroo toxin? Symptoms?

Irreversible binding/blocking of nicotinic acetylcholine receptors. Causes paralysis

83

What is edrophonium used for? MOA?

Used to diagnose myasthenia gravis.

Short acting, reversible cholinesterase inhibitors

84

What is the MOA of sarin?

Irreversibly binds acetylcholine inhibitors

85

True or false: irreversible inhibition of acetylcholine receptors is always poisonous

True

86

What are the three features a neurotransmitter must have to be defined as a neurotransmitter?

1. Packed into a vesicle
2. Ca-dependent release
3. Binds to specific receptors

87

What are the three major categories of neurotransmitters?

1. Small molecule
2. Neuroactive
3. Gaseous neurotransmitters

88

What is the unconventional neurotransmitter that does not fit into the three major classes of neurotransmitters?

Endocannabinoids

89

Which class of neurotransmitter is Acetylcholine?

Small molecule

90

What is the receptor for acetylcholine at neuromuscular junctions?

Nicotinic acetylcholine receptor

91

What are the two major types of acetylcholine receptors?

Nicotinic (fast, ionotropic)
Muscarinic (slow, metabotropic)

92

Which type of neurotransmitters are biogenic amines classified as?

Small molecule

93

What are the three biogenic amines?

1. Catecholamines
2. Serotonin
3. Histamine

94

What are the three catecholamines discussed in lecture?

Dopamine
Norepi
Epi
(all share common Y derivation)

95

What type of receptors for epi and norepi bind to?

Adrenergic/noradrenergic receptors

96

What defines a catecholamine? Is 5HT a catecholamine?

All share a common Y derivative

5HT is NOT a catecholamine, but is a biogenic amine

97

What type of neurotransmitter is serotonin? What amino acid is it derived from?

biogenic amine

Derived from W

98

What type of neurotranmitter is histamine?

biogenic amine

99

What are the amino acid neurotransmitters?

1. GABA
2. Glycine (G)
3. Glutamate (E)
4. Aspartate (D)

100

What is the major inhibitory neurotransmitter?

GABA

101

What are the two main classes of GABA?

A and B

102

What is the receptor for GABAa?

ligand gated Cl- channel

103

What is the receptor for GABAb?

a metabotropic receptor which has an inhibitory effect by opening K+ channels or suppression of Ca++ channels.

104

What is the efffect of glycine (inhibition or excitation)?

Inhibition

105

What type of receptor does Glycine bind to?

Ion gated Cl- channel

106

What is the effect of strychnine?

Blocks Glycine receptors

107

What are the two excitatory amino acid transmitters?

E and D

108

What are the three different classes of glutamate receptors?

AMPA
Kainate
NMDA

109

What ion blocks the NMDA in Glutamate pathways until the postsynaptic membrane is slightly depolarized through stimulation of other excitatory receptors.

Mg

110

The NMDA receptor channel (that binds glutamate) is permeable to what three ions?

Ca, Na, and K

111

What receptor is believed to have an important role in memory and learning

Glutamate

112

What is excitotoxicity?

Destruction of neurons by an unusually high accumulation of glutamate and related compounds

113

What are the four types of "small molecule" neurotransmitters?

Acetylcholine
Amino acids
Purines
Biogenic amines

114

What are the purine neurotranismitters?

ATP and Adenosine

115

Is adenosine stored in vesicles?

No

116

What is the general effect of adenosine?

Depressant

117

What is the MOA of caffeine, theophylline, and theobromine?

All block adenosine

118

What are the receptors for adenosine called?

Adenosine receptors

119

What does ATP (as a neurotransmitter) bind to

P-type purinergic receptors

120

Where are peptide precursor molecules that act as neurotransmitters synthesized? Where do they complete their maturation?

Synthesized in the nucleus, then packed into vesicles with enzymes and sent down neuron where they mature

121

Where are small molecule neurotransmitters usually synthesized?

At the end of the axon

122

Neuropeptides can coexist in same nerve terminals with classic transmitters. What causes their release?

LARGE amounts of Ca (They are not released at active zones since the vesicles are too large to fit into the docking complex)

123

What type of neurotransmitter are opioids?

Neuropeptide

124

What type of neurotransmitter are vassopressin and oxytocin?

Neuropeptides

125

What are the three endogenous opioid families?

Endorphins
Enkephalins
Dynorphins

126

What is the one gaseous neurotransmitter?

NO

127

How is NO produced?

by the action of the enzyme nitric oxide synthase

128

How NO synthase regulated?

The enzyme is regulated by Ca++ binding to the Ca++ sensor protein calmodulin.

129

True or false: NO is contain in synaptic vesicles

False- it is released as soon as it is made to affect nearby cells

130

What class of neurotransmitter are ananamide and 2-arachidonylglycerol?

Endocannaboids

131

How are endocannaboids produced?

Via enzymatic degradation of membrane lipids

132

What are the two types of endocannaboid receptors?

CB1 and CB2

133

What does THC bind to?

CB1 and CB2