Neurotransmitters Flashcards
Which 3 structures of a neurone allow for synaptic transmission?
- Dendrites —> receive information
- have spine structures - Soma —> integrate information received
- Axon —> transmits action potential
What is a synapse?
Gap between 2 neurones that neurotransmitters travel across
- 20-100 nm
- 100s-1000s per neurone
What are the 3 stages of synaptic transmission?
- Neurotransmitter biosynthesis, packing and release
- Receptor action
- Inactivation
What are the 6 steps of activation of a CNS synapse?
- Na+ influx and K+ efflux —> depolarisation of pre-
synaptic neurone - Ca2+ influx (200µM) —> NT vesicle fuses with
membrane (4,000-10,000 NT molecules per vesicle) - NT exocytosis —> diffusion across synapse
- NT binds to receptor on post-synaptic neurone —>
Na+ influx —> new AP - NT leaves receptor via enzymatic breakdown or
transfer via channel protein —> activation stops - Na+/K+ ATPase pump restores pre-synaptic
neurone potential
What are the 3 types of neurotransmitters?
- Amino acids —> glutamate
—> GABA
—> glycine - Amines —> NA (noradrenaline)
—> DA (dopamine) - Neuropeptides —> opioid peptides
What are the 6 steps in the cycle of a synaptic vesicle?
Exocytosis:
1. Endosome forms
2. Budding —> of endosome —> vesicle
3. Docking —> at synaptic zone
4. Priming —> vesicle proteins added
5. Fusion —> proteins on vesicle and membrane bind
Endocytosis:
6. Budding —> of neurone membrane —> endosome
What are 2 examples of neurotoxins targeting vesicular proteins?
- Alpha latrotoxin —> stimulates VGCCs
- Botulinium toxin —> inhibits vesicle proteins
What are the 2 types of neurotransmitter receptor?
- Ion channel-linked receptors —> fast (msecs)
- Na+, Ca2+, Cl- across
- G-protein-couples receptors —> slow (secs/mins)
- effectors —> enzymes or channels
What are the 4 examples of neurotransmitters that bind to ion-channel linked receptors?
CNS:
1. Glutamate —> GluR
- stimulatory
2. GABA —> GABAR
- inhibitory
3. Glycine —> GlyR
- inhibitory
NMJ:
4. ACh —> nAChR (nicotinic acetylcholine receptor)
What are the 5 examples of neurotransmitters that bind to G-protein-couples receptors?
- ACh —> muscarinic receptors
- DA (dopamine)
- NA (noradrenaline)
- 5HT (serotonin)
- Neuropeptides - eg. enkephalin
How do excitatory vs inhibitory receptors work?
Excitatory - Na+ influx —> depolarisation (over -65mV)
Inhibitory - Cl- influx —> hyperpolarisation (under -65)
What are the 2 types of glutamate receptors?
- AMPA receptors:
- Na+ influx —> fast excitatory transmission
- NMDA receptors:
- Na+ and Ca2+ influx —> Ca2+ 2nd messenger —>
slow excitatory transmission
- Na+ and Ca2+ influx —> Ca2+ 2nd messenger —>
What are the 3 steps in the synaptic transmission of glutamate?
- Release: Glutamate synthesis (TCA cycle +
transamination) —> exocytosis - Activation: Reversibly binds to AMPA and NMDA
receptors —> Na+ and Ca2+ influx - Deactivation: Glutamate leaves receptors —>
EAATs (excitatory amino acid transporters) —> into
pre-synaptic neurones (reuse) and glial cells
(converted to glutamine by glutamine synthetase)
What are the 4 steps in the synaptic transmission of GABA?
- Release: GABA synthesis by GAD (glutamic acid
decarboxylase) —> exocytosis - Activation: Reversibly binds to GABARs receptors
—> Cl- influx - Deactivation: GABA leaves receptors —> GATs
(GABA transporters) —> into pre-synaptic neurones
(reuse) and glial cells (converted to succinic
semialdehyde by GABA-transaminase)
What causes seizures?
Excess glutamate
- possible issues with glutamate —> glutamine in glial
cells
