Neurotransmitters Flashcards
Name the parts of a neurone
Spins, Dendrites, Soma, Axon, Synaptic terminal
What is the gap between neurones at a synapse?
20 - 100 nm
List the 3 stages of synaptic transmission.
- Biosynthesis, packaging and release of neurotransmitters
- Receptor action
- Inactivation
What are the 2 most important neurotransmitters in the brain?
Glutamate - excitatory
GABA - inhibitory
Outline the sequence of events in neurotransmitter release.
Membrane depolarisation Ca2+ channels open Ca2+ influx Vesicle fusion Vesicle exocytosis Transmitter release Endocytosis of empty vesicle
What enables vesicle fusion and exocytosis?
Special vesicular proteins
How does tetanus toxin act?
Breakdown of cholinergic transmission and therefore paralysis
What does botulinum toxin do?
Causes flaccid paralysis
How does alpha latrotoxin work?
Causes uncontrolled influx of Ca2+ and therefore depletion of neurotransmitter.
How does entry of Ca2+ at the presynaptic membrane cause an effect?
Vesicular fusion and exocytosis of neurotransmitters from the plasma membrane
Do ion channel receptors create a fast or slow response?
Fast
Do G-protein coupled receptors create a fast or slow response?
Slow
What is the effector of a G-protein coupled receptor?
Enzymes - adenyl cyclase
Channels - Ca2+
Neurotransmitters for ion channel receptors (CNS)?
Glutamate
GABA
Neurotransmitters for ion channel receptors (NMJ)?
ACh at nicotinic receptors
Neurotransmitters for G-protein coupled receptors (CNS and PNS)?
ACh at muscarinic receptors Dopamine Noradrenaline Serotonin Neuropeptides
How does an inhibitory neurotransmitter receptor work?
Cl- influx, membrane potential becomes more negative (hyper polarisation)
How does an excitatory neurotransmitter receptor work?
Na+ influx, membrane depolarisation
What are the two types of glutamate receptor?
AMPA - fast
NMDA - slow
What abnormality at synapses is associated with seizures?
Excess glutamate
What are the stages of an excitatory CNS synapse?
- Glutamate synthesised from glucose via TCA cycle & transamination
- Glutamate reversibly binds post-synaptic receptors (linked to ion channels)
- Rapid uptake of glutamate by excitatory amino acid transporters (EAATs)
- Glutamate enzymatically modified by glutamine synthetase to glutamine in glial cell
What are the stages of an inhibitory CNS synapse?
- GABA formed by decarboxylation of Glutamate by glutamic acid decarboxylase (GAD)
- GABA reversibly binds post-synaptic receptors (linked to ion channels)
- Rapid uptake of glutamate by GABA transporters (GATs)
- GABA enzymatically modified by GABA-transaminase to succinate semialdehyde in glial cell
How many subunits make up a GABA receptor?
5
