Neurotransmission Flashcards
What are the four main sections of the typical neuronal structure?
- Cell soma
- Dendrites
- Axon
- Terminals
What effect does depolarisation in the terminal have in neurotransmission?
It opens voltage-gated Ca2+ channels, and Ca2+ ions enter the terminal
What effect does the entrance of Ca+ ions into the terminal have in neurotransmission?
It causes the vesicles to fuse and release neurotransmitter
What happens to the neurotransmitter released from the terminal in neurotransmission?
It diffuses across the synaptic cleft, and binds to receptors on the post-synaptic membrane
What does the post-synaptic response depend on in neurotransmission?
- Nature of the transmitter
- Nature of the receptor
Give two examples of receptors found in neurotransmission
- Ligand-gated ion channels
- G-protein coupled receptors
How many neurotransmitters have been identified in the CNS?
Over 30
What chemical classes can the neurotransmitters in the CNS be divided into?
- Amino acids
- Biogenic amines
- Peptides
Give 5 examples of biogenic amine neurotransmitters in the CNS
- Acetylcholine
- Noradrenaline
- Dopamine
- Serotonin
- Histamine
Give 6 examples of peptide neurotransmitters in the CNS
- Dynorphin
- Enkephalins
- Substance P
- Somatostatin
- Cholecystokinin
- Neuropeptide Y
What are the types of amino acid neurotransmitters?
- Excitatory amino acids
- Inhibitory amino acids
What is the main excitatory amino acid neurotransmitter?
Glutamate
What % of all CNS synapses are glutamatergic?
Over 70%
Describe the distribution of glutamatergic neurotransmitters in the CNS
They are present throughout the CNS
Give two inhibitory amino acid neurotransmitters
- GABA
- Glycine
What are the types of glutamate receptors?
- Ionotrophic
- Metabotrophic
What are the types of ionotropic glutamate receptors?
- AMPA receptors
- Kainate receptors
- NMDA receptors
Describe a ionotrophic glutamate receptor
It is an ion channel that is permeable to Na+ and K+, and in some cases Ca2+
What does activation of ionotrophic glutamate receptors cause?
Depolarisation, and therefore increased excitability
What are the types of metabotrophic glutamate receptors?
mGluR 1-7
What kind of receptor are the metabotrophic glutamate receptors?
G-protein coupled receptors
What does activation of metabotrophic glutamate receptors lead to?
Either;
- Changes in IP3 and Ca2+ metabolism
- Inhibition of adenylate cyclase, and decreased cAMP levels
What effect do excitatory neurotransmitters have on the post-synaptic cell?
They cause depolarisation
How do excitatory neurotransmitters cause depolarisation of the post-synaptic cell?
By acting on ligand-gated ion channels
What is it called when excitatory neurotransmitters cause depolarisation of the post-synpatic cell?
Excitatory post-synaptic potential
What does depolarisation of the post-synaptic cell by excitatory neurotransmitters cause?
More action potentials
What kind of receptors do glutamatergic synpases have?
Both AMPA and NMDA
What do AMPA receptors in glutamatergic synapses mediate?
The initial fast depolarisation
What are NMDA receptors permeable to?
Ca2+
What do NMDA receptors require to allow ion flow through the channel?
Need glutamate to bind, and the cell to be depolarised
What acts as a co-agonist to NMDA receptors in the glutamatergic synapses?
Glycine
Where do glutamate receptors have an important role?
In learning and memory
What effect can activation of NMDA receptors and mGluRs have on AMPA receptors?
Can up-regulate them
What does strong, high frequency stimulation to glutamate receptors cause?
Long term potentiation
What is important for the induction of LTP?
Ca2+ entry through NMDA receptors
What does too much Ca2+ entry through NMDA receptors cause?
Excitotoxicity
What is the result of too much Ca2+ entry through NMDA receptors causing excitotoxicity?
Too much glutamate can cause excitotoxicity
What is the main inhibitory neurotransmitter in the brain?
GABA