Synaptic Transmission Flashcards
How can neuronal morphology be mapped?
using a golgi stain
What is an electrical synapse?
a synapse with no gap between the pre and post-synaptic terminals, action potential travels directly
What is a chemical synapse?
action potential travels by neurotransmitters being released from a presynaptic terminal and acting on postsynaptic receptors
What is an axodendritic synapse?
an axon connecting to a dendrite (most common)
What is an axosomatic synapse?
an axon connecting to a soma
What is an axoaxonic synapse?
an axon connecting to another axon
What are classical neurotransmitters?
amino acids; glutamate, GABA, glycine
monoamines; DA, NE, 5-HT
acetylcholine
What are non-classical neurotransmitters?
neuropeptides
gases
lipids
How are classical neurotransmitters synthesised?
dietary precursors cross the BBB where enzymes in the axon terminals synthesise them into neurotransmitters and pack them into vesicles
How are non-classical neurotransmitters synthesised?
neuropeptide transmitters are synthesised in the cell body
What are the 3 R’s of neurotransmitter storage?
readily releasable pool; docked to cell membrane, rapid release, rapid depletion
recycling pool; mobilised by moderate stimulation, fairly rapid release
reserve pool; mobilised by intense stimulation, slow release
What factors determine neurotransmitter release?
rate of cell firing
probability of neurotransmitter release
presence of auto receptors on axon terminals
What are the functions of auto receptors?
terminal; inhibit further neurotransmitter release
somatodendritic; slow the rate of cell firing
What happens during receptor binding?
NT rapidly diffuse across narrow synaptic cleft
binding to any receptors in the vicinity
often significant spillover into nearby synapses
What mechanisms are used during inactivation?
reuptake
enzyme degradation
What is reuptake?
reuptake transporters suck NT back into the presynaptic terminal
What is enzyme degradation?
processes such as metabolism excretion and cycling rapidly degrade the NT’s
What percent of action potentials trigger NT release?
10-20%
What is signal transduction?
transmitters bind to a receptor changing the conformation and elicit intracellular changes
What is an ionotropic receptor?
a ligand-gated channel that opens to allow the flow of ions; receptor conformation is changed
What are the effects of an ionotropic receptor?
fast and rapidly reversible
What are the types of ionotropic receptor?
NDMA
AMPA
Kainate
What are the features of NMDA receptors?
found on dendritic spines
slower neurotransmission
a magnesium block is removed when there is a high firing rate
What are the features of AMPA receptors?
found on dendritic spines
most fast excitatory responses to glutamate are mediated by AMPA
What are metabotropic receptors?
g-protein-coupled receptors
single proteins with 7 transmembrane domains
indirectly influence cellular activity through a cascade of events
slower signalling than ionotropic
By what mechanisms can g-proteins signal?
direct coupling to an ion channel which inhibits/stimulates the channel
coupling to a second messenger (effector enzyme) system
How do second messenger systems work?
second messengers activate protein kinases which activate other second messenger systems by phosphorylation
What is a colour metric reaction?
antibodies can detect antigens, secondary antibodies can detect primary antibodies and produces a colour close to the initial protein
What is a fluorescence reaction?
antibodies can be used to detect an antigen (proteins), secondary antibodies detect the primary antibody which have fluorophores which glow when light is shined on them
What are gene regulatory pathways?
second messengers can alter gene transcription or regulation by activating transcription factors
