Weeks 7-9 Flashcards
Electrical transmission
Direct flow of ions from one neurone to another. E.g gap junction
What modulates gap junctions?
pH, conc of Ca2+, NTs
How many connexins make up a connexon?
6
Stages of neurotransmission
1) A.A. NTs synthesised in axon terminal. Peptide NTs formed in soma.
2) NT take up in to vesicles
3) Rise in intracellular [Ca2+] cause NT to be released in to cleft.
4) NT binds on post synaptic membrane.
5) NT broken down/reuptake/diffuses away from synapse.
Examples of amine NTs
Dopamine (DA) NA Adrenaline Histamine 5-HT
Example of A.A NTs
GABA
Glutamate (Glu)
Glycine (Gly)
Examples of peptide NTs
Somatostatin
Substance P
Co-existence/Co-transmission
A single neurone that sythesises and releases more than one NT.
Synaptic vesicle cycling
Docked vesicle release NT by exocytosis.
Fused vesicle membrane is taken up into the cell by endocytosis.
Role of SNARE proteins
Synaptobrevin: vesicle docking
Synaptotagmin: Ca2+ fusion
Metabotropic receptors
Coupled to intracellular proteins that transduce signal (slow)
Ionotropic receptors
Form ion channels that depolarise or hyperpolarise postsynaptic cell (fast).
Temporal summation
Same neuron firing more rapidly
Spatial summation
More than one neuron
Synaptic potential definition
Difference in voltage between the inside and outside of the post synaptic neurone.
Glutamate
Major excitatory NT
Generates EPSP
Too much glutamate causes
Excitotoxicity
GABA
Generates IPSP by firing Cl-
NTs involved in pain
Substance P (peptide) signals pain.
Opioids inhibit substance P release.
3 ways signal is terminated
Inactivation of NT
Reuptake of NT
Diffusion away from synapse
NMDA receptor
Glutamate and glycine bind here.
NMDA receptors allow the flow of Na+, K+ and Ca2+
Structure of metabotropic receptors
7 transmembrane domains
Domains 2,3,6,7 bind NT
G-proteins bind to loop between domains 5 and 6
Activation of ion channel via GPCR
1) NT binds to receptor
2) Activates G-protein
3) G protein activates effector protein
4) Effector protein activates 2nd messenger pathway
5) 2nd messenger lead to metabolic changes in postsynaptic cell
6) Opening/closing of ion channel
