CNS synapses and neurotransmitters Flashcards
what is a chemical synapse?
-neurotransmitters cross a synaptic cleft to postsynaptic structure
what is an electrical synapse?
- gap junctions
- direct passage of current
what are cell adhesion molecules? why are they important?
- transmembrane proteins that bridge the synapse
- critical for synapse formation and structural plasticity
postsynaptic receptors are coupled to scaffolding proteins, which then link to ____________. what does this protein-protein interaction do?
- postsynaptic receptors are coupled to scaffolding proteins, which then link to cytoskeletal proteins
- through these interactions, neurotransmission can lead to structural and functional changes to the synapses
go through the 7 steps of the chemical synapse
- precursors enter the cell
- Neurotransmitter synthesis
- vesicular transporter (package NT)
- Postsynaptic receptor(binds to NT and exhibits a response)
- Release-modulating autoreceptor (on presynaptic side to regulate presynaptic terminal)
- Presynaptic re-uptake transporter (sits on membrane of pre and recycles NT back into pre as it starts to accumulate)
- Astrocyte clearance (clears excess NT)
what is the difference between neurtransmitters and neuropeptides?
- Neurotransmitters: enzymes and vesicles are transferred from the soma to the axon terminal, then the NT is synthesized in terminal
- Neuropeptide: synthesized in soma, then vesicle and NT are transported to the axon terminal
what are the two ways a NT can get into a vesicle?
- Proton pump (ATP dependent)
- Proton/Transmitter anti-porter
-NT use electrochemical gradient to get into the vesicle
what are the two exceptions to NT sequestrantion into a vesicle?
- when NT are synthesized inside of a vesicle
2. Neuropeptides
in resting state, most vesicles are tethered by ______ and not yet docked.
actin
what happens after AP and Calcium influx?
- actin filaments de-polymerize and dis-associate from vesicles
- vesicles dock, fuse, and release, then are recycled
name some amino acid neruotransmitters
- Glutamate(excitatoy)
- aspartate
- GABA (inhibitory)
- Glycine(inhibitory)
- histamine
what are the two categories of biogenic amines?
- catecholamines
- indolamines
name some catecholamines
- dopamine
- norepi
- epi
what is an indolamine?
serotonin (from brain stem neurons)
what is a retrograde messengers?
- released from post-synaptic neuron and act on Pre-synaptic neuron
- regulates neurotransmitter release
what are some examples of retrograde messengers?
-endocannabinoids
-NO
CO
what precursors and enzyme make acetylcholine?
Acetyl CoA + Choline
cholineacetyltransferase
where do we get choline?
-diet or synthesized in liver
where would you find acetylcholine?
forebrain and midbrain
what is the functional significance of acetylcholine?
- memory and attention
- reward seeking behavior
- arousal
- sleep cycle
what is the major excitatory NT in the CNS?
L-glutamate
what are the three sources of Glutamate and what is the enzyme?
- 2 from mitochondria and 1 from astrocytes
- glutamate dehydrogenase
what happens to AMPA glutamate receptors when there is an influx of Calcium and EPSP? what happens when there is lack of stimulation or IPSP?
Calcium influx: addition of more AMPA glutamate receptors
IPSP: removal of AMPA glutamate receptors
AMPA and Kainate receptors select for what ions? what type of channel are they?
- Potassium and calcium
- ligand gated
NMDA receptors select for what ions?
-potassium, calcium, and sodium
why are ionotropic receptors excitatory?
they let their cations in, which makes the potential less negative and pushes it to threshold
what is the purpose of the Mg site in NMDA receptors?
-acts as a block and depolarization releases the block
increased amounts of glutamate means increased amounts of calcium, which can result in what?
necrosis and cell death
what is the major inhibitory NT in the CNS?
GABA
GABA is synthesize from what and by what?
from glutamate by glutamic acid decaroxylase
what is GABA metabolized by?
mitochondrial enzymes
what does GABA(a) receptor do?
it hyperpolarizes to make potential more negative
what is the clinical significance of GABA?
- deficiency results in increase in neuronal excitability
- GABA dysfunction leads to seizures
what is the clinical significance of glutamate?
- concept of glutamate excitotoxicity
- target for general anesthetics
what NT is important for neuronal plasticity?
glutamate (learning/memory)
