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Neuroscience and mental health > neurotransmitters > Flashcards

neurotransmitters Flashcards

1
Q

what is neurotransmission

A

information transfer across a synapse
requires neurotransmitters and their interaction with postsynaptic membranes
abnormalities in this cause psychiatric and neurological disorders including Parkinson’s, epilepsy and schizophrenia
40% genome involved

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2
Q

Features of neurotransmission

A 
rapid 
diversity - many genes involved 
adaptability 
plasticity 
learning and memory
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3
Q

describe membrane plasticity

A

changes in the responses

modified by the nature of the response and structural changes in the number of synapses

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4
Q

describe adaptability of neurotransmission

A

dynamic and changing all the time

change in input to cells and pathways by environmental stimuli

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5
Q

what makes neurotransmission diverse

A

the receptor on the second cell

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6
Q

describe the 3 stags of synaptic transmission

A
  • biosynthesis, packaging and release of NT
  • synaptic activation of the second cell - receptor cation
  • signal integration and conduction by the second cell - integration of all inputs
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7
Q

how does the structure of the neuron relate to neurotransmission

A

spines on the dendrites receive information - information reception
soma - integration and regulation of other inputs
axon - electrical part, rapid transfer of the action potential
nerve endings and terminals - synapses to downstream cell

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8
Q

what is the time frame of chemical transmission

A

for the AP to go from the 1st to 2nd cell it takes 2ms

events between this take fractions of ms

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9
Q

features of the synapse

A

presynaptic terminal/nerve ending
gap 20-100nm - enough to be resistance to electrical signals so chemical signal needed
postsynaptic region with receptors - receptive area either dendrite or cell soma
mitochondria
synaptic vesicle - with NT. some electron dense with NT, others less so
post-synaptic density - the high number of proteins in signalling pathway and those that regulate activity of the downstream cell

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10
Q

what does T stand for in a synaptic vesicle

A

typical NT

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11
Q

describe neurotransmission

A

diverse
may mediate rapid us-ms (thought) or slower effects ms
vary in abundance from mM to nM in CNS
neurons receive many inputs which are integrated to produce a single effect

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12
Q

Types of neurotransmitter

A

Amino Acid
amines
neuropeptides

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13
Q

amino acid neurotransmitters

A

glutamate - excitatory - intermediary metabolism, TCA cycle, transfer of amino groups in many pathways, most potent AA - only need small quantities (10 to the -15mol), most abundant
gamma amino butyric acid - as important as glutamate, inhibitory
glycine - in brain stem and spinal chord, less common present in mmol concentration

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14
Q

what are the amine NT

A

acetyl choline
noradrenaline
dopamine

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15
Q

neuropeptide NT

A

opioid peptides

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16
Q

order of abundance of NT from high to low

A

AA
amine
neuropeptides

17
Q

describe the sequence of events in the activation of the synapse

A

Na enters the presynaptic neuron because of depolarisation
outflow of potassium
calcium entry - through calcium channel
NT release into synapse
NT bind to receptor - allow Na into postsynaptic nuron through ion channel - depolarisation
NT enter presynaptic neuron - removed to stop action potential at postsynaptic neuron
K enter pre-synaptic neuron by ATP transporter
Na leave pre-synaptic neuron using ATP
replenish vesicles for next AP

18
Q

essential components of synaptic transmission

A 
restricted to the synapse 
fast - 200us 
calcium increase to 200um locally 
synaptic vesicles containing 4000-100000 molecules each 
vesicles close proximity to membrane 
some fuse and release NT
19
Q

what is the relationship between Ca and NT release

A

electrical - biophysical event
electromechanical transduction
200us

20
Q

how does rapid release of NT occur

A

proteins on vesicle membrane and neuron membrane
vesicles filled with NT docked
the a-helix of the proteins overlap - vesicles stay associated in active zone, relatively stable
Ca entry activates a ca sensor (synapototagmin) in the protein complex - conformational change - promote fusion of membrane and opening of pore. Calcium sensitive complex response
exocytosis

21
Q

neurotoxin targets

A

tetanus - target vesicular proteins - paralysis - block NT release
botulinum toxin - vesicular and membrane proteins - placid paralysis - block NT release
Latrotoxin - prevent exocytosis and resealing of the membrane

22
Q

What is required for NT release

A

vesicles docked to presynaptic membrane
protein complex formation between vesicle, membrane and cytoplasmic regions - allow docking and rapid response to Ca entry
ATP and vesicle recycling

23
Q

ion channel receptors

A

fast - us-ms
mediate all fast excitatory and inhibitory transmission
transmitter bind
conformational change eg with synapototagmin
diversity and rapid information flow
many subunit conformations

24
Q

G-protein coupled receptor

A

slow - s/mins
transduce response to recptor and effector
effectos can be enzymes eg adenyl cyclase - cAMP - PK - activate key protein, phospholipase C, cGMP-PDE
or channels ca/k

25
Q

Glutamate receptor

A

GLUR
dendritic spines
excitation
open Na channel - polarise

26
Q

GABA receptor

A 
GABAR 
chloride entry 
-ve charge 
hyperpolarised 
raise threshold for response 
inhibitory 
typically on soma
27
Q

GlyR

A

similar to GABAR

higher cl conductance

28
Q

effect of receptors on membrane potential

A

increase in membrane potential - glutamate

negative membrane potential - GABA

29
Q

describe the different types of glutamate receptors

A

classical - AMPA receptors, fast excitatory synapses, rapid onset offset and desensitisation - cause depolarisation
NMDA - slow component, serve as coincidence detectors underly learning mechanisms (events happen after each other and change the response Ca activated phosphorylation receptor - alter transcription - make new synapse and protein, understand the learning process, only operate when cell is already depolarised, calcium enters with Na, Ca modifies AMPA - potentiating the response - activating protein synthesis which modifies synapse formation

30
Q

what happens at an excitatory synapse

A

mediated my glutamate

linked to intermediary metabolism 
a-ketoglutarate is in the vesicles 
glutamate transporter (GLUR) on post-synaptic membrane 
excitatory amino acid transporter (EAAT) has high capacity to take glutamate up into the glial cell, EAAT abundant in glial and neuron cells 
in glial cells glutamate -- glutamine catalysed by glutamine synthetase. in nerve cell the glutamine returns to the vesicles
31
Q

what does AMPA receptors stand for

A

alpha amino-3-hydroxy-5methyl-4-isoxole- propanoic acid

32
Q

what does NMDA stand for

A

N-methyl-D aspartate

33
Q

what happens if there is extra glutamate in the synapse

A

seizures
electrical activity increases
glutamate converted to glutamine

34
Q

what happens at an inhibitory CNS synapse

A

mediated by GABA which has a similar structure to glutamate
intermediary metabolism - glutamate
glutamate — GABA catalysed by glutamate acid decarboxylase (GAD [B6])
on post synaptic membrane - GABAaR (GABA receptors)
hyperpolarise membrane, threshold increases
GABA transporter (GAT) - GABA into glial cells
GABA - succinate semialdehyde catalysed by GABA transaminase (GABA-T) which goes into TCA cycle
in nerve cell GABA is returned to vesicles

35
Q

describe the pentameric organisation of the GABA receptor and binding domains

A

on the receptor the binding channels are: steroids, benzodiazepines, Zn, convulsant, ethanol, barbiturates

36
Q

describe the action of drugs on GABAaR

A

the drugs modulate the activity of the receptor
modify GABA activated chloride response - opening of the channel is modified at allosteric sites
benzodiazepines - important inhibitory action
antiepileptic, anxiolytic, sedative, muscle relaxant - all enhance GABA transmission - important for treatment of epilepsy

37
Q

what is epilepsy treatment’s focus

A

dampens excitatory activity
facilitate inhibitory transmission
target the GABA synapse

38
Q

why is chemical transmission used at a synapse rather than electrical

A

transferred in a concise space - electrical signal would need a larger SA

Neuroscience and mental health (14 decks)

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