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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
All neurons in the CNS release which neurotransmitter?
ACh (all preganglionic nerve fibers)
26
Vesicles of presynaptic neurons that harbor ACh
Cholinergic neurons
27
What enzyme synthesizes ACh?
Choline acetyltransferase (ChAT)
28
Choline is mostly obtained from (diet or metabolism)
Diet
29
ACh is formed from ______ and _____ via ChAT
Choline and ACoA
30
The choline transporter is a (Na+ / K+ / Ca++) dependent transporter that moves choline into nerve terminal
Na+-dependent
31
ACh is transported into vesicles from the cytoplasm by which type of transporters?
Vesicle associated transporters (VATs)
32
What signals the release of ACh?
Action potential that depolarizes from Ca++ uptake
33
In the release of acetylcholine, ______ fuses with ______ via a ______ that is an ATP-dependent process and results in exocytosis of ACh
VAT fuses with SNAP via SNARE
34
Where is the "ready releasable pool" of ACh located?
Near the nerve terminal
35
What is the action of the ACh "reserve pool"
Fill up the ready releasable pool after it has been used
36
Which enzyme degraded ACh in the synaptic cleft, which is required to reset the cholinergic receptor?
Acetylcholinesterase
37
Alternative enzyme in the body that degrades many types of esters such as ACh, as well as substances such as heroin and cocaine (opiates)
Butylcholinesterase
38
What is the overall action of Botox (botulinum toxin) on ACh release in neuromuscular junctions?
Prevents SNAPS binding with SNARES, so ACh can't be released
39
Which neurotransmitter is the principle transmitter of most sympathetic postganglionic fibers (especially in CNS)
NE
40
Which is the primary hormone of the adrenal medulla (especially found in blood or periphery)?
EPI
41
Neurons that secrete epinephrine/norepinephrine
Adrenergic
42
Term used to describe neurons that produce mostly norepinephrine
Noradrenergic
43
Three major catecholamines
Norepinephrine, epinephrine, dopamine
44
Which amino acid are the three major catecholamines derived from?
L-tyrosine
45
This enzyme converts phenylalanine to L-tyrosine to help make catecholamines
Phenylalanine hydroxylase
46
Disease characterized by the absence of phenylalanine hydroxylase that is usually overcome by restricting phenylalanine in the diet
Phenylketonuria
47
What enzyme is the rate-limiting step in catecholamine biosynthesis, and what is it mostly inhibited by?
Tyrosine hydroxylase; inhibited by catecholamines
48
Steps of formation of epinephrine from L-tyrosine (4 steps)
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
Where in the body is NE converted to EPI?
Adrenal medulla
50
What part of the NE and EPI structure give them their activity?
Beta-hydroxy group (on the carbon chain off the aromatic ring)
51
Secretion of which class of hormones helps to control the rate of formation of EPI and by what method of action?
Glucocorticoids bind to chromaffin cells in the adrenal medulla, which induces PNMT activity
52
Two methods of interrupting actions of catecholamines
1. Reuptake into nerve terminus | 2. Degradation of catecholamines
53
Which transporter moves roughly 90% of NE from the synaptic cleft into the nerve terminal cytoplasm?
NET (norepinephrine transporter)
54
Which transporter moves catecholamines from cytoplasm to storage vesicles
VMAT2 (Vesicular monoamine transporter)
55
How is the action of VMAT2 driven?
Driven by pH and proton gradient that is established by ***V-type ATPase***
56
Transporter that moves catecholamines into extraneuronal cells
ENT
57
What are the two key enzymes that metabolize catecholamines?
1. Monamine oxidase (MAO) | 2. Catechol-O-methyltransferase (COMT)
58
Generally, where does most metabolism of neurotransmitters occur?
In the cells where they are synthesized
59
Which catecholamine metabolizing enzyme is found on the outer surface of mitochondrion and uses oxygen and FAD as cofactors?
MAO
60
Which catecholamine metabolizing enzyme is mostly found in cytoplasmic/soluble protein extraneuronal cells and present as membrane-bound enzyme in adrenal cells?
COMT
61
Which catecholamine metabolizing enzyme is found in high concentrations in liver and kidney, but NOT in sympathetic neurons (brain)
COMT
62
Where is MAO assumed to be found?
In every tissue where catecholamines (monoamines) would be synthesized/degraded)
63
When degrading catecholamines, aldehyde conversion depends on the present of which group?
Beta hydroxy group (present in EPI and NE) | Not present in Dopamine
64
Presence of a beta hydroxy group on a catecholamine favors degradation by what enzyme?
Aldehyde reductase (AR)
65
Lack of beta hydroxy group on catecholamine favors oxidation by which enzyme?
Aldehyde dehydrogenase
66
Dopamine's aldehyde intermediate is
DOPAL
67
NE/EPI aldehyde intermediate is
DOPEGAL
68
Dopamine is degraded by ____ to DOPAL, then _____ oxidizes DOPAL to DOPAC. DOPAC is then methylated by _____ in peripheral tissues to what substance?
MAO; AD; COMT --> results in homo vanillic acid (HVA)
69
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.
MAO; AR; then goes to liver
70
MHPG from norepinephrine is oxidized to alcohol dehydrogenase and _____ to form VMA
Aldehyde dehydrogenase (AD)
71
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 ____
COMT; MAO; to VMA in liver
72
Which class of amino acid neurotransmitters frequently cause inhibition, and give some examples (4 total)
Monocarboxylic acids such as: 1. GABA 2. Glycine 3. Taurine 4. Beta-alanine
73
Which class of amino acid neurotransmitters frequently cause excitation, and give some examples (2 total)
Dicarboxylic acids 1. Glutamate 2. Aspartate
74
GABA is synthesized by which pathway?
GABA shunt pathway
75
What is an important intermediate from the Kreb's cycle that is important in GABA synthesis?
Alpha-ketogluterate
76
What is the purpose of the GABA shunt pathway?
Synthesize and conserve pools of GABA
77
Which enzyme transaminates alpha-ketogluterate to L-glutamate in the GABA shunt pathway?
Alpha-oxogluterate transminase
78
Which enzyme converts L-glutamate to GABA?
GABA decarboxylase
79
How can the GABA shunt pathway contribute to the Kreb's cycle?
Provides succinic acid by converted succinic semialdehyde using a dehydrogenase
80
Depolarization of which neuron stimulates GABA transmission?
GABAergic
81
GABA action is terminated by reuptake. What two factors does reuptake of GABA depend on?
Temperature and ions
82
This neurotransmitter is associated with mental-well-being and modulates smooth muscle in the cardiovascular system and platelet aggregation
Serotonin
83
This neurotransmitter is closely related to serotonin's structure, and is synthesized in response to light while regulating biological rhythms
Melatonin
84
What happens if someone has too much serotonin (6 total), and what is the main cause?
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
What happens if there is too little serotonin? (4 total)
1. Deficient serotonergic activity 2. Depression 3. Low self-esteem 4. OCD
86
What amino acid is serotonin produced from?
Tryptophan
87
What enzyme is used to convert tryptophan to serotonin?
1. Tryptophan hydroxylase | 2. L-amino acid decarboxylase (AADC)
88
What enzyme is the rate limiting step when synthesizing serotonin?
Tryptophan hydroxylase
89
What is special about the regulation of tryptophan hydroxylase?
Tryptophan hydroxylase is not inhibited by end product inhibition - it is modified genetically
90
Tryptophan hydroxylase uses which cofactors?
O2 and tetrahydropterine
91
AADC uses which cofactor?
Vitamin B6
92
Which enzymes are used in serotonin degradation?
1. MAO | 2. AD (aldehyde dehydrogenase)
93
What is the major catabolite of serotonin?
5-hydroxyindole acetic acid
94
Which system involves direct innervation of skeletal muscle without ganglionic relay?
Somatic
95
Which system involves unconscious, automatic actions such as breathing, heart rate and urination, and can be broken down into two parts?
Autonomic
96
Fight or flight branch of autonomic nervous system with WIDELY distributed effectors throughout body
Sympathetic
97
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
Parasympathetic
98
Parasympathetic and sympathetic neurotransmitters often serve as function (agonists / antagonists) to one another
Antagonists

Biochem II (7 decks)

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