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Physiology > Exam I | Neurotransmitters and Synapses > Flashcards

Exam I | Neurotransmitters and Synapses Flashcards

1
Q

Describe the 5 steps of release of neurotransmitter from the pre-synaptic cell to the post-synaptic cell.

A

1) AP arrives at axon terminal of presynaptic cell
2) Voltage-gated Ca2+ channels open with depolarization, allowing influx of ions
3) Ca2+ binds regulatory proteins initiating exocytosis
4) Vesicles release NT into synaptic cleft
5) Molecules diffuse into and across cleft to bind post-synaptic receptors
5) Response in post-synaptic cell (depolarization or signaling sequence) is initiated

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2
Q

When Volatge-gated Ca2+ channels open, is the concentration of Ca2+ greater on the inside or outside?

A

outside

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3
Q

What happens in EPSP?

A

neurotransmitter passes postsynaptic cell membrane

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4
Q

What happens upon post-synaptic cell binding of a neurotransmitter?

A
  • can inhibit or excite post-synaptic neuron (depending on the nature of receptors) by altering the membrane
  • post-synaptic cell may respond to receptor binding by altering metabolism, secretion, or transcription
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5
Q

Does neurotransmitter activity depend more on the neurotransmitter type or the receptor characteristics?

A

receptor characteristics

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6
Q

Receptors on a post-synaptic cell can be what two things?

A
  • ion channel

- G-protein cascade initiator

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7
Q

What 2 ways can neurotransmitter receptors initiate a response in the post-synaptic cell?

A
  • directly or indirectly gating an ion channel (ligand-gated)
  • initiating a 2nd messenger cascade
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8
Q

What 3 advantages does 2nd messenger cascade have over direct/indirect gating of an ion-channel?

A
  • signal amplification
  • greater regulation of pathway
  • flexibility (diverse responses)
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9
Q

What is the receptor for GABA? What is the result of GABA binding?

A
  • Receptor is a Cl2+ channel

- binding of GABA causes hyperpolarization and inhibition (IPSP)

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10
Q

What is G protein involved in?

A

second messenger signaling

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11
Q

What are two ways cell signaling pathways can be simplified?

A
  • ionotropic (“fast”) synaptic potentials

- metabotropic (“slow”) synaptic potentials

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12
Q

Describe ionotropic synaptic potentials.

A
  • fast. binding of nt causes immediate change in membrane potential
  • direct or “almost” opening of a ligand-gated ion channel
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13
Q

Describe metabotropic synaptic potentials.

A
  • slower, more persistent response than ionotropic
  • involves 2nd messenger signaling (usually G-protein)
  • membrane potential may change after intermediary reactions
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14
Q

What do nicotinic and amino acid neurotransmitters have in common?

A

they are ligand-gated (receptor is ionotropic)

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15
Q

What are the 4 ionotropic receptors (include the neurotransmitter that binds them)?

A
  • nicotinic (Ach)
  • NMDA &AMPA (glutamate)
  • receptor for GABA
  • receptor for glycine
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16
Q

What is Ach short for?

A

acetyl-choline

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17
Q

What are the 5 metabotropic receptors (include the neurotransmitter that binds them)?

A
  • muscarinic (Ach)
  • alpha, beta (adrenaline)
  • D1, D2, etc. (dopamine)
  • 5-HTs, except for 5-HT3 (serotonin)
  • membrane (peptides)
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18
Q

Is Ach binding to nicotinic receptors excitatory or inhibitory?

A

excitatory

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19
Q

Is GABA excitatory or inhibitory?

A

inhibitory

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20
Q

What neurotransmitters fall under the amine class?

A
  • dopamine
  • serotonin
  • adrenaline
  • histamine (not on chart)
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21
Q

What amines are subclassified as catecholamines? Why?

A
  • adrenaline (epinephrine) histamine, norepinephrine, and dopamine
  • they are synthesized by tyrosine
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22
Q

What neurotransmitters are classified as amino acids?

A
  • GABA
  • Glycine
  • Glutamate
  • and Aspartate (not on chart)
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23
Q

Distinguish an agonist from an antagonist.

A
  • agonist is chemical that performs normal response

- antagonist is chemical that blocks normal response

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24
Q

Tryptophan hydroxylases synthesize what neurotransmitter?

A

serotonin

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25
Q

MAO stands for what?

A

Monoamine oxidase

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26
Q

What do MAO and COMT catabolize?

A

the amines (serotonin, dopamine, and adrenaline)

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27
Q

What is the descriptive name for Ach activity, and what class does Ach fall under?

A

cholinergic

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28
Q

What are the descriptive names for adrenaline, dopamine, and serotonin activity?

A
  • adrenergic
  • dopaminergic
  • serotonergic
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29
Q

What are the descriptive names for glutamate, GABA, and glycine activity?

A
  • glutamatergic
  • GABAergic
  • glycinergic
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30
Q

What are the receptors for Ach? Are they fast or slow?

A
  • nicotinic (fast)

- muscarinic (slow)

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31
Q

What are the receptors for the amines? Are they fast or slow?

A
  • adrenaline: alpha and beta,
  • dopamine: D1, D2, etc.,
  • serotonin: 5HTs, except 5HT3.
  • all are slow
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32
Q

What are the receptors for the amino acids? Are they fast or slow?

A
  • Glutamate: NMDA and AMPA
  • GABA: GABA
  • Glycine: no receptor
  • all are fast
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33
Q

What are the enzymes that synthesize and catabolize Ach, respectively?

A
  • choline acetyl-transferase (CHAT) synthesizes

- acetyl-cholinesterase (ACHE) catabolizes

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34
Q

CHAT stands for what?

A

choline acetyl-transferase

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35
Q

ACHE stands for what?

A

acetyl-cholinesterase

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36
Q

Ach receptor antagonists

A
  • curare, alpha-bungarotoxin (nicotinic)

- atropine & scopolamine (muscarinic)

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37
Q

Adrenaline receptor antagonist

A

alpha or beta blockers, inhibitors

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38
Q

dopamine receptor antagonist

A

haloperidol, chlorpromazine

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39
Q

serotonin receptor antagonist

A

clozapine, etc. (for 5-HT2A)

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40
Q

glutamate receptor antagonist

A

ketamine, dextromethorpan

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41
Q

GABA receptor antagonist

A

block inhibition, have stimulant effects

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42
Q

glycine antagonists

A

none

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43
Q

What is the abbreviation for nicotinic acetylcholine receptors?

A

nAChR

44
Q

What are the cholinergic receptors?

A

nicotinic & muscarinic

45
Q

Nicotinic receptor importance

A
  • receptors of neuromuscular junction

- first part of sympathetic and parasympathetic nervous system

46
Q

What are the 3 types of nicotinic receptors?

A
  • N: CNS
  • G: ANS
  • M: skeletal muscle
47
Q

What are the AGONISTS of nicotinic receptors?

A
  • nicotine

- choline

48
Q

What are the antagonists of nicotinic receptors?

A
  • snake venom alpha-bungarotoxin (neurotoxin)

- curare

49
Q

Are nicotinic receptors ionotropic or metabotropic?

A

ionotropic

50
Q

Muscarinic receptor

A
  • finish parasympathetic NS
  • broad distribution throughout CNS
  • GI functions such as salivation, increasing stomach acid
51
Q

Are muscarinic receptors isotropic or metabotropic?

A

metabotropic

52
Q

What are the 5 muscarinic receptors, and where are they found?

A
  • M1: (CNS, stomach)
  • M2 (heart, brainstem)
  • M3 (smooth muscle)
  • M4 and M5 (basal nuclei)
53
Q

Which muscarinic receptors inhibit?

A

M2 and 4

54
Q

Which muscarinic receptors excite?

A

M1, M3, and M5

55
Q

M2: what is it, where is it found, and what does it do?

A
  • inhibitory muscarinic receptor
  • found in heart
  • decreases heart rate, force, and AV conduction
56
Q

M3:, what is it, where is it found, and what does it do?

A
  • excitatory muscarinic receptor
  • found in smooth muscle and exocrine glands
  • involved in glandular secretion and all smooth muscle contraction EXCEPT vasodilation
57
Q

What classifies something as a catecholamine?

A

being derived from tyrosine

58
Q

What are 4 aminergic neurotransmitters?

A
  • adrenaline and dopamine (catecholamines)
  • serotonin
  • histamine
59
Q

What are the adrenergic neurotransmitters?

A

epinephrine and norepinephrine

60
Q

What do the adrenergic receptors bind to?

A

alpha or beta receptors

61
Q

What are the 3 catecholamines?

A
  • norepinephrine
  • adrenaline (epinephrine)
  • dopamine
62
Q

What are neurocrines and give 2 examples?

A
  • both hormone and nuerotransmitters

- epinephrine and norepinephrine

63
Q

epinephrine and norepinephrine both fall under what two classes?

A

catecholamines and neurocrines

64
Q

what are alpha and beta receptors critical to? Are they metabotropic or ionotropic?

A
  • sympathetic (ANS) activation

- metabotropic

65
Q

alpha 1 receptors

A
  • cause sympathetic VASOCONSTRICTION of arterial smooth muscle
  • cause relaxation of GI smooth muscle
66
Q

alpha 2 receptors

A

largely inhibitory

67
Q

beta 1 receptors

A

tend to upregulate cardiac function

68
Q

beta 2 receptors

A

-cause VASODILATION of blood vessel

69
Q

importance of dopamine (2 points to remember)

A
  • involved in movement control, motivation, reward, and reinforcement
  • many addictive substances work by affecting dopaminergic neurons
70
Q

what does an autoreceptor do? Give an example

A
  • regulates reuptake and catabolism of neurotransmitter

- dopamine re-uptake transporter

71
Q

What are MAO-B and COMT enzymes?

A

catabolic enzymes that target all catecholamines

72
Q

Describe what happens at the dopaminergic synapse (4 steps)

A
  • AP arrives at synapse
  • calcium-dependent exocytosis releases dopamine
  • unbound dopamine is re-uptaken by presynapse
  • that dopamine is then degraded/recycled by MAO-B COMT
73
Q

What does SSRI stand for, and what does it do?

A
  • selective serotonin reuptake inhibitor

- increases amount of serotonin at the synapse

74
Q

What does SNpc stand for?

A

substantia nigra pars compacta (black area of brainstem)

75
Q

What anomaly is associated with Parkinson’s symptoms?

A

loss of dopamine at the dopaminergic synapses of the substantia nigra pars compacta (SNpc)

76
Q

schizophrenia is associated with what anomaly?

A

overactive dopamine

77
Q

What are the 4 dopaminergic pathways?

A

1) mesocortical
2) tuberoinfundibular
3) mesolimbic
4) nigrostriatal

78
Q

What dopaminergic pathway is most important for motor function, and where does it originate and end?

A
  • nigrostriatal pathway

- extends from brainstem up to the striatum

79
Q

What is the brain’s dopaminergic fundamental reward pathway?

A

Mesolimbic pathway

80
Q

What dopaminergic pathway is involved with mood and social interactions? To where does it extend?

A
  • mesocortical pathway

- extends into forebrain

81
Q

what are the dopamine receptors?

A

D1-like

D2-like

82
Q

What are the D1-like receptors? What do they do? Are they excitatory or inhibitory?

A
  • include D1 and D5
  • couple to G-alpha-olf or G-alpha-s and activate adenyl cyclase (AC)
  • act to regulate Ca channels, also modulate NMDA receptors
  • are excitatory
83
Q

What are D2-like receptors? What do they do? Are they excitatory or inhibitory?

A
  • include D2, D3, & D4
  • coupled to G-alpha-i/o, which inhibits the AC-cAMP-PKA transduction pathway
  • are inhibitory
84
Q

What is the proper name for serotonin?

A

5-HT

85
Q

What 3 areas is serotonin found in?

A
  • GI tract (90%)
  • CNS
  • platelets
86
Q

Where do serotonergic pathways originate?

A

raphe nuclei of brainstem

87
Q

What are the functions of serotonin?

A
  • regulates motility and secretion in GI tract
  • act as a vasoconstrictor at sites of bleeding
  • regulates mood, sleep, appetite, memory formation
  • modulates activity of other neurotransmitters
88
Q

How many receptors are there for serotonin? Are they ionotropic or metabotropic?

A
  • there’s 12

- all are metabotropic except 5-HT3

89
Q

What mediates serotonin re-uptake?

A

SERT transporter

90
Q

What inhibits the SERT transporter?

A
  • SSRI
  • MDMA
  • amphetamine
  • cocaine
91
Q

Insufficiency of serotonin can lead to what?

A
  • neonate death
  • OCD
  • depression/anxiety
92
Q

What is acetylcholinesterase? Where is it located?

A
  • chops up and degrades acetylcholine in the synaptic cleft before it binds to receptors
  • may or may not be located on the post-synaptic cell
93
Q

What would an MAO inhibitor do in aminergic synapse?

A
  • would cause aminergic to accumulate in the pre-synaptic cell
  • resulting greater concentration within the cell would cause transporter to stop bringing in aminergic
94
Q

Distinguish aminergic and cholinergic disposal at the synapse.

A
  • cholinergics are not re-uptaken by the pre-synapse; only the debris caused by acetylcholinesterase, which cleaves/degrades Ach before it binds to receptors on post-synapse
  • excess aminergics are re-uptaken and degraded by MAO and COMT
95
Q

What are the 3 amino acid neurotransmitters? are they excitatory or inhibatory?

A
  • aspartate, excitatory
  • glutamate, excitatory
  • glycine, inhibatory
96
Q

What is the difference between AMPA and NMDA receptor?

A
  • NMDA is voltage-gated and ligand-gated

- AMPA is only voltage gated (Na+ channels)

97
Q

What is required for the activation of NMDA?

A
  • binding of a ligand, usually glutamate and glycine (can be 2 glutamates)
  • voltage-gating is dependent on Mg2+ or Zn2+ binding
98
Q

What does NMDA stand for

A

N-methyl-D-aspartate

99
Q

NMDA is involved in what processes?

A

learning, memory, and synaptic plasticity

100
Q

What ions hyperpolarize the cell?

A

K+ and Cl2-

101
Q

What is the difference between GABA A and GABA B receptors?

A
  • GABA A is much more abundant, ionotropic (Cl2- channel)

- GABA B is metabotropic (G-protein receptor)

102
Q

How is GABA recycled?

A
  • by glial cells (astrocytes) that turn it into glutamine

- by the presynaptic cell

103
Q

GABA A receptor

A
  • hyperpolarizes as Cl2- enters cell

- has binding sites for sedatives (benzodiazepines and alcohol) and steroids, which enhance hyperpolarization,

104
Q

Most antidepressants target what pathway?

A

catecholamine

105
Q

List the major classes of antidepressants in general order of use.

A
  • Selective Serotonin Reuptake Inhibitors (SSRIs)
  • Serotonin and Norepinephrine Reuptake Inhibitors (SNRIs)
  • Atypical Antidepressants
  • Tricyclic and Tetracyclic
  • MAO inhibitors (MAOi)
106
Q

What is the receptor for glutamate?

A

NMDA & AMPA

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