Chapter 1: chemical neurotransmission Flashcards

1
Q

axodendritic synapse

A

signals from the axon of one neuron to the dendrite of another

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2
Q

axosomatic synapse

A

signal sent from the axon of one neuron to the soma of another

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3
Q

axoaxonic synapse

A

signal from the axon of one neuron to the axon of another

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4
Q

anterograde communication

A

trasmission of thesignal fromthe axon of one neuron to the axon, dendrite, or soma of the next neuron

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5
Q

neurons

A

cells of chemical communcation in the brain

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6
Q

chemically addressed nervous system

A

how signals are coded, decoded, transduced, and sent along the way

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7
Q

neurotransmitters

A

serotonin
norepinephrine
dopamine
acetylcholine
glutamate
GABA
b-endorphin (body’s morphine)
endocannabinoids (body’s pot

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8
Q

what is involved in neuron input

A

can involve many different neurotransmitters coming from many different neuronal circuits

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9
Q

types of neurotransmission

A

classic, retrograde, volume

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10
Q

classic neurotransmission

A

electrical impulses are sent through neuron until it is changed to chemical signal. then chemical messenger is hurled from one neuron to the next where it is either converted back to an electrical impulse or triggers a cascade of chemical messages to change the neurons molecular and genetic functioning

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11
Q

excitation-secretion coupling

A

process of converting the electrical impulse in a neuron to the chemical signal at the synapse between neurons

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12
Q

retrograde neurotransmission

A

when postsynaptic neuron talks back to presynaptic neuron

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13
Q

chemical produced specifically as retrograde neurotransmitters at some synapses

A

endocannabinoids (EC)
nitric oxide (NO)
nerve growth factor (NGF)

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14
Q

retrograde neurotransmission of endocannabinoids (EC)

A

interacts with CB1 (cannabinoid receptor 1) in presynaptic neuron

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15
Q

retrograde neurotransmission of nitric acid

A

interacts with cGMP in presynaptic neuron

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16
Q

retrograde neurotransmission of nerve growth factor (NGF)

A

taken up in presynaptic neuron vesicles to travel back to cell nucleus to interact with the genome there

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17
Q

volume neurotransmission

A

do not require synapses

when chemical messengers are sent into the synapse they may spill over to distant sites with compatible receptors through diffusion

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18
Q

excitation-secretion coupling

A

process of electrical impulse being converted to chemical signal

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19
Q

basic description of excitation-secretion coupling

A

electrical impulse enters axon terminal of presynaptic neuron and stimulates release of chemical neurotransmitter

electrical impulse opens ion channel by changing charge across the neuronal membrane

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20
Q

How does a VSSC work

A

sodium flows into the presynaptic nerve through the axonal membrane causing the electrical charge there to move along the axon to the presynaptic nerve terminal where it opens up calcium channels

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21
Q

How does a VSCC work

A

after receiving signal from VSSC, calcium flows into the presynaptic nerve terminal causing the synaptic vesicles to spill their chemical contents into the synapse

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22
Q

what makes it possible for the genome of one neuron to communicate with the genome of another

A

signal transduction cascades

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23
Q

basic description of signal transduction cascades

A

A first messenger neurotransmitter activates the production of a second chemical messenger that then activates a third messenger enzyme (known as a kinase) that adds phosphate groups to a fourth messenger protein to create phosphoproteins

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24
Q

what are the two main targets of signal transduction

A

phosphoproteins and genes

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25
Q

how is signal transduction reversed for retrograde communication between neurons

A

The first messenger neurotransmitter opens an ion channel that allows calcium to enter the neuron and act as the second messenger which then activates a third messenger (enzyme known as a phosphatase) which removes the phosphate groups from the fourth messenger phosphoproteins and thus reverses the action of the third messenger

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26
Q

what is determined by the balance of kinase and phosphatase in signal transduction cascades

A

the degree of chemical activity that gets translated into the active fourth messenger

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27
Q

what does the active fourth messenger trigger

A

diverse biological responses such as gene expression and synaptogenesis

28
Q

what are the four signal transduction cascades

A

g-protein linked systems
ion-channel linked systems
hormone linked systems
neurotrophins

29
Q

how is a second messenger formed in g-protein linked signal transduction cascade

A

neurotransmitter (first messenger) binds to receptor site to change it so it can bind with the G protein. Once G protein is bound it changes shape so it can bind to an enzyme that can synthesize the second messenger

30
Q

what is the second messenger in G-protein linked signal transduction cascades

A

a chemical

31
Q

what is the second messenger in ion-channel linked signal transduction cascades

A

an ion (like calcium or sodium)

32
Q

how is the second messenger formed in hormone-linked signal transduction cascades

A

hormone binds to its receptor in the cytoplasm to form a hormone-nuclear receptor complex

33
Q

how is the second messenger formed in neurotrophin signal transduction cascades

A

there is a complex set of various second messengers that trigger each other

34
Q

structure of inactive protein kinase exist

A

a dimer made of 2 copies of the enzyme protein kinase, each with a regulatory unit

35
Q

how does inactive protein kinase become an active third messenger

A

2 copies of the second messenger cAMP cause the regulatory unit to detach from each inactive enzyme in the dimer. Once the regulatory units detach the enzymes split apart and are now active 3rd messengers

36
Q

what is phosphorylation and how does it happen

A

active third messenger kinases shoot phosphate groups into proteins to create 4th messenger phosphoproteins

37
Q

how is active third messenger protein phosphatase synthesized

A

neurotransmitter (1st messenger) opens ion channel that allows calcium (second messenger) to enter and activate third messenger protein phosphatase

38
Q

what is dephosphorylation

A

when third messenger protein phosphatase rips phosphate groups off of phosphoproteins

39
Q

how are phosphoproteins activates

A

some by phosphorylation (uses kinase)
some by dephosphorylation (uses phosphatase)

40
Q

what are the things that activation of phosphoproteins can do

A

change the synthesis of neurotransmitters
alter neurotransmitter release
change the conductance of ions
maintain chemical neurotransmission apparatus in a state or dormancy

41
Q

what is the ultimate cellular function of neurotransmission

A

to turn a gene on or off (all 4 signal transduction pathways end with this goal)

42
Q

what is the difference between a signal transduction cascade and a signal transduction pathway

A

there are 4 cascades that end with generation of a phosphoprotein.
there are 2 pathways from the third messenger to the fourth messenger in the signal transduction cascade

43
Q

which 2 signal transduction cascades are triggered by neurotransmitters

A

G-protein linked receptor cascades
Ion channel linked receptor cascades

44
Q

what system do the 2 neurotransmitter signal transduction cascades act on

A

CREB system (responds to protein phosphorylation)

45
Q

how do g-protein linked receptors act on CREB

A

the g-protein linked receptor activates protein kinase A
THEN
the activated receptor goes into the cell nucleus to stick a phosphate group to CREB
THEN
this activates the transcription factor that causes nearby genes to be expressed

46
Q

how do ion channel linked receptors act on CREB

A

they enhance intracellular calcium (second messeger) levels which interact with calmodulin protein to activate certain kinases
THEN
these kinases translocate into the cell nucleus to add a phosphate group to CREB

47
Q

what can activate both kinases and phosphatases

A

calcium

48
Q

how does hormone signal transduction cascade target genes

A

hormones bind cytoplasmic receptors to produce a hormone-nuclear receptor complex that can translocate into the cell nucleus
THEN
the complex finds elements in the gene it can influence (HREs)
THEN
it acts as a transcription factor to trigger activation of genes

49
Q

how do neurotrophin cascades trigger gene expression

A

first messengers (neurotrophins) activate one kinase after another until one finally phosphorylates a transcription factor in the nucleus to start transcribing genes

50
Q

how does neurotransmission trigger gene expression

A

chemical info message is passed along “pony express” from molecular rider to molecular rider until it reaches the right phosphoprotein mailbox in the postsynaptic neuron

51
Q

how much DNA is occupied by genes

A

only a few %

52
Q

2 regions of a gene

A

regulating region
encoding region

53
Q

regulating region of genes

A

transcription factor is activated by phosphorylation of protein kinase
THEN
the activated transcription factor can bind to the regulatory region of the gene
THEN
RNA polymerase is activated

54
Q

coding region of gene

A

enzyme RNA polymerase transcribes DNA into its mRNA
THEN
mRNA translates itself into the corresponding protein that will activate the gene

55
Q

what does an early immediate gene do

A

functions as a rapid responder to neurotransmitter input

56
Q

cJun and cFos

A

nuclear proteins (leucine zippers) team up to form the zipper transcription factor that activates later onset genes

57
Q

what happens when the product of two early genes is a transcription factor (like with leucine zippers)

A

it returns to the genome to activate late genes

58
Q

what are the products of late genes

A

any protein the neuron needs:
enzyme
transporter factors
growth factors

59
Q

what determines which late genes get activated

A

which neurotransmitter is sending the message
how frequently it sends the message

whether it is working with/against other neurotransmitters that are talking to other parts of the same neuron at the same time

60
Q

what is epigenetics

A

system that determines whether or not a gene is actually made into its RNA and protein or if it is ignored

61
Q

how are genes turned on/off

A

by modifying the structure of chromatin in the cell nucleus

62
Q

what determines the character of a cell

A

its chromatin

63
Q

structure of chromatin

A

8 histones that DNA are wrapped around (nucleosome)

64
Q

what does chromatin have to do with genes

A

its structure determines whether a gene is expressed or silenced

65
Q

chemical modifications that can modify the structure of chromatin

A

methylation
acetylation
phosphorylation

66
Q

what regulates acetylation and methylation of chromatin

A

neurotransmission
drugs
environment