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Biochem II > Exam 2 Neurotransmitters > Flashcards

Exam 2 Neurotransmitters Flashcards

1
Q

Chemical substance released at a nerve terminal that carries an impulse across a synaptic cleft to a postsynaptic receptor

A

Neurotransmitter

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2
Q

Compartments that store neurotransmitters in the presynaptic neuron

A

Synaptic vessicles

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3
Q

Target proteins that bind a neurotransmitter and elicit responses at smooth, cardiac, skeletal muscles, exocrine glands and postynaptic neurons

A

Neurotransmitter receptors

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4
Q

Cholinergic neurotransmitter

A

Acetylcholine

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5
Q

Adrenergic and dopaminergic neurotransmitter

A

Catecholamines

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6
Q

Serotinergic neurotransmitter

A

Serotonin

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7
Q

Two main amino acid based neurotransmitters

A

GABA and glutamate

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8
Q

What system of the body is the nicotinic receptor a part of?

A

Somatic system

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9
Q

What neurotransmitter acts on nicotinic receptors?

A

ACh

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10
Q

What tissue are nicotinic receptors found?

A

Skeletal muscle (striated)

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11
Q

Where does the motor neuron in the somatic system originate?

A

Various levels of the spinal cord

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12
Q

Do motor neurons in the somatic system use ganglions to relay neurotransmitters to the target tissue?

A

No

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13
Q

What system are muscarinic receptors found?

A

Autonomic nervous system (both Parasympathetic and Sympathetic)
*Sympathetic are sweat glands

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14
Q

What tissues are muscarinic receptors found in?

A

Smooth muscle, cardiac tissue, secretory glands

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15
Q

Which neurotransmitter acts on muscarinic receptors?

A

ACh

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16
Q

In the parasympathetic system, where is the origin of the neurons?

A

Cranial and spinal

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17
Q

In the sympathetic nervous system, where is the origin of the neurons?

A

Thoracic and lumbar

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18
Q

Do the parasympathetic and sympathetic systems use ganglions?

A

Yes

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19
Q

What receptors are present in the ganglions of the autonomic nervous system?

A

Nicotinic

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20
Q

Preganglionic neurons in the sympathetic system release which neurotransmitter to the adrenal medulla?

A

ACh

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21
Q

The adrenal medulla takes ACh and converts it to which two neurotransmitters and in what %?

A

Epi/NE ; 80%/20%

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22
Q

Postganglionic neurons in the sympathetic system release what neurotransmitter to ________ receptors in the sweat glands

A

ACh; muscarinic receptors

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23
Q

Postganglionic neurons in the sympathetic system release what neurotransmitter to _______ receptors in smooth muscle, cardiac tissue, and secretory glands

A

NE; adrenergic receptors

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24
Q

Postganglionic neurons in the parasympathetic system release what neurotransmitter to ______ receptors in smooth muscle, cardiac tissue, and secretory glands

A

ACh; muscarinic receptors

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25
Q

All neurons in the CNS release which neurotransmitter?

A

ACh (all preganglionic nerve fibers)

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26
Q

Vesicles of presynaptic neurons that harbor ACh

A

Cholinergic neurons

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27
Q

What enzyme synthesizes ACh?

A

Choline acetyltransferase (ChAT)

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28
Q

Choline is mostly obtained from (diet or metabolism)

A

Diet

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29
Q

ACh is formed from ______ and _____ via ChAT

A

Choline and ACoA

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30
Q

The choline transporter is a (Na+ / K+ / Ca++) dependent transporter that moves choline into nerve terminal

A

Na+-dependent

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31
Q

ACh is transported into vesicles from the cytoplasm by which type of transporters?

A

Vesicle associated transporters (VATs)

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32
Q

What signals the release of ACh?

A

Action potential that depolarizes from Ca++ uptake

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33
Q

In the release of acetylcholine, ______ fuses with ______ via a ______ that is an ATP-dependent process and results in exocytosis of ACh

A

VAT fuses with SNAP via SNARE

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34
Q

Where is the “ready releasable pool” of ACh located?

A

Near the nerve terminal

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35
Q

What is the action of the ACh “reserve pool”

A

Fill up the ready releasable pool after it has been used

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36
Q

Which enzyme degraded ACh in the synaptic cleft, which is required to reset the cholinergic receptor?

A

Acetylcholinesterase

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37
Q

Alternative enzyme in the body that degrades many types of esters such as ACh, as well as substances such as heroin and cocaine (opiates)

A

Butylcholinesterase

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38
Q

What is the overall action of Botox (botulinum toxin) on ACh release in neuromuscular junctions?

A

Prevents SNAPS binding with SNARES, so ACh can’t be released

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39
Q

Which neurotransmitter is the principle transmitter of most sympathetic postganglionic fibers (especially in CNS)

A

NE

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40
Q

Which is the primary hormone of the adrenal medulla (especially found in blood or periphery)?

A

EPI

41
Q

Neurons that secrete epinephrine/norepinephrine

A

Adrenergic

42
Q

Term used to describe neurons that produce mostly norepinephrine

A

Noradrenergic

43
Q

Three major catecholamines

A

Norepinephrine, epinephrine, dopamine

44
Q

Which amino acid are the three major catecholamines derived from?

A

L-tyrosine

45
Q

This enzyme converts phenylalanine to L-tyrosine to help make catecholamines

A

Phenylalanine hydroxylase

46
Q

Disease characterized by the absence of phenylalanine hydroxylase that is usually overcome by restricting phenylalanine in the diet

A

Phenylketonuria

47
Q

What enzyme is the rate-limiting step in catecholamine biosynthesis, and what is it mostly inhibited by?

A

Tyrosine hydroxylase; inhibited by catecholamines

48
Q

Steps of formation of epinephrine from L-tyrosine (4 steps)

A
  1. L-tyrosine –> L-DOPA via tyrosine hydroxylase
  2. L-DOPA –> Dopamine via DOPA decarboxylase
  3. Dopamine –> NE via Dopamine beta hydroxylase
  4. NE –> EPI via PNMT
49
Q

Where in the body is NE converted to EPI?

A

Adrenal medulla

50
Q

What part of the NE and EPI structure give them their activity?

A

Beta-hydroxy group (on the carbon chain off the aromatic ring)

51
Q

Secretion of which class of hormones helps to control the rate of formation of EPI and by what method of action?

A

Glucocorticoids bind to chromaffin cells in the adrenal medulla, which induces PNMT activity

52
Q

Two methods of interrupting actions of catecholamines

A
  1. Reuptake into nerve terminus

2. Degradation of catecholamines

53
Q

Which transporter moves roughly 90% of NE from the synaptic cleft into the nerve terminal cytoplasm?

A

NET (norepinephrine transporter)

54
Q

Which transporter moves catecholamines from cytoplasm to storage vesicles

A

VMAT2 (Vesicular monoamine transporter)

55
Q

How is the action of VMAT2 driven?

A

Driven by pH and proton gradient that is established by V-type ATPase

56
Q

Transporter that moves catecholamines into extraneuronal cells

A

ENT

57
Q

What are the two key enzymes that metabolize catecholamines?

A
  1. Monamine oxidase (MAO)

2. Catechol-O-methyltransferase (COMT)

58
Q

Generally, where does most metabolism of neurotransmitters occur?

A

In the cells where they are synthesized

59
Q

Which catecholamine metabolizing enzyme is found on the outer surface of mitochondrion and uses oxygen and FAD as cofactors?

A

MAO

60
Q

Which catecholamine metabolizing enzyme is mostly found in cytoplasmic/soluble protein extraneuronal cells and present as membrane-bound enzyme in adrenal cells?

A

COMT

61
Q

Which catecholamine metabolizing enzyme is found in high concentrations in liver and kidney, but NOT in sympathetic neurons (brain)

A

COMT

62
Q

Where is MAO assumed to be found?

A

In every tissue where catecholamines (monoamines) would be synthesized/degraded)

63
Q

When degrading catecholamines, aldehyde conversion depends on the present of which group?

A

Beta hydroxy group (present in EPI and NE)

Not present in Dopamine

64
Q

Presence of a beta hydroxy group on a catecholamine favors degradation by what enzyme?

A

Aldehyde reductase (AR)

65
Q

Lack of beta hydroxy group on catecholamine favors oxidation by which enzyme?

A

Aldehyde dehydrogenase

66
Q

Dopamine’s aldehyde intermediate is

A

DOPAL

67
Q

NE/EPI aldehyde intermediate is

A

DOPEGAL

68
Q

Dopamine is degraded by ____ to DOPAL, then _____ oxidizes DOPAL to DOPAC. DOPAC is then methylated by _____ in peripheral tissues to what substance?

A

MAO; AD; COMT –> results in homo vanillic acid (HVA)

69
Q

Norepinephrine in sympathetic neuron is degraded by ____ to DOPEGAL, then reduced by _____ to DHPG. DHPG then travels to the _____ where it is methylated by _____ to form MHPG.

A

MAO; AR; then goes to liver

70
Q

MHPG from norepinephrine is oxidized to alcohol dehydrogenase and _____ to form VMA

A

Aldehyde dehydrogenase (AD)

71
Q

In extraneruonal cells, epinephrine is methylated by ____ to metanephrine, then deanimated by ____ to MHPG. MHPG is then brought to liver where alcohol dehydrogenase and aldehyde dehydrogenase oxidize it to ____

A

COMT; MAO; to VMA in liver

72
Q

Which class of amino acid neurotransmitters frequently cause inhibition, and give some examples (4 total)

A

Monocarboxylic acids such as:

  1. GABA
  2. Glycine
  3. Taurine
  4. Beta-alanine
73
Q

Which class of amino acid neurotransmitters frequently cause excitation, and give some examples (2 total)

A

Dicarboxylic acids

  1. Glutamate
  2. Aspartate
74
Q

GABA is synthesized by which pathway?

A

GABA shunt pathway

75
Q

What is an important intermediate from the Kreb’s cycle that is important in GABA synthesis?

A

Alpha-ketogluterate

76
Q

What is the purpose of the GABA shunt pathway?

A

Synthesize and conserve pools of GABA

77
Q

Which enzyme transaminates alpha-ketogluterate to L-glutamate in the GABA shunt pathway?

A

Alpha-oxogluterate transminase

78
Q

Which enzyme converts L-glutamate to GABA?

A

GABA decarboxylase

79
Q

How can the GABA shunt pathway contribute to the Kreb’s cycle?

A

Provides succinic acid by converted succinic semialdehyde using a dehydrogenase

80
Q

Depolarization of which neuron stimulates GABA transmission?

A

GABAergic

81
Q

GABA action is terminated by reuptake. What two factors does reuptake of GABA depend on?

A

Temperature and ions

82
Q

This neurotransmitter is associated with mental-well-being and modulates smooth muscle in the cardiovascular system and platelet aggregation

A

Serotonin

83
Q

This neurotransmitter is closely related to serotonin’s structure, and is synthesized in response to light while regulating biological rhythms

A

Melatonin

84
Q

What happens if someone has too much serotonin (6 total), and what is the main cause?

A
  1. Excessive serotonergic activity (duh.. idk what that means though)
  2. Hypertensive emergencies
  3. Hyperactive reflexes
  4. Diarrhea
  5. Agitation
  6. Hyperthermia

Main cause of excessive serotonin is from medications like SSRIs and MAOIs

85
Q

What happens if there is too little serotonin? (4 total)

A
  1. Deficient serotonergic activity
  2. Depression
  3. Low self-esteem
  4. OCD
86
Q

What amino acid is serotonin produced from?

A

Tryptophan

87
Q

What enzyme is used to convert tryptophan to serotonin?

A
  1. Tryptophan hydroxylase

2. L-amino acid decarboxylase (AADC)

88
Q

What enzyme is the rate limiting step when synthesizing serotonin?

A

Tryptophan hydroxylase

89
Q

What is special about the regulation of tryptophan hydroxylase?

A

Tryptophan hydroxylase is not inhibited by end product inhibition - it is modified genetically

90
Q

Tryptophan hydroxylase uses which cofactors?

A

O2 and tetrahydropterine

91
Q

AADC uses which cofactor?

A

Vitamin B6

92
Q

Which enzymes are used in serotonin degradation?

A
  1. MAO

2. AD (aldehyde dehydrogenase)

93
Q

What is the major catabolite of serotonin?

A

5-hydroxyindole acetic acid

94
Q

Which system involves direct innervation of skeletal muscle without ganglionic relay?

A

Somatic

95
Q

Which system involves unconscious, automatic actions such as breathing, heart rate and urination, and can be broken down into two parts?

A

Autonomic

96
Q

Fight or flight branch of autonomic nervous system with WIDELY distributed effectors throughout body

A

Sympathetic

97
Q

Rest and digest branch of autonomic nervous system with LIMITED distribution to effectors through the body, and in many cases is in close proximity to organs it innervates

A

Parasympathetic

98
Q

Parasympathetic and sympathetic neurotransmitters often serve as function (agonists / antagonists) to one another

A

Antagonists

Biochem II (7 decks)

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