Flashcards in lecture 29 - Synaptic transmission Deck (40):
1
glutamate transporter
removes glutamate to presynaptic terminals and astrocytes. Other transporters take it to be stored in synaptic vesicles
2
what are the 2 classes of neurotransmitters?
- small molecule neurotransmitters ('classical')
- neuropeptides ('neuromodulators')
3
substance P and endorphins
neuropeptides
4
synapse found in retina
electrical synapse
5
what does the increase of permeability to Cl-, due to IPSPs, cause ?
decreased cell membrane resistance. They make the current induced by EPSPs less efficient in bringing postsynaptic membrane to threshold.
6
metabotropic
indirectly gated glutamate receptors
7
how are most amino acids inactivated?
re-uptake
8
factors affecting synaptic action:
(a) type of neurotransmitter/neuroregulator
(b) type of neurotansmitter receptor expressed in post-synaptic membrane/ multiple receptor subtypes
(c) number of neurotransmitter receptors in the postsynaptic membrane - synaptic plasticity
9
Direct gating of ion channels (characteristics and features)
- transmitter binds directly to the ion channel complex and the pore opens
- very fast onset
- short-lived
10
neuromuscular junction =
chemical synaptic transmission between the axon terminals of motoneurons and the end-plates of muscle fibres
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features of classical, small molecule neurotransmitters
fast action, acting directly
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how small are the postsynaptic potentials?
around 0.1mV
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AMPA, Kainate
directly gated glutamate receptors
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too much glutamate release (or insufficient re-uptake) will lead to...
excitotoxicity: too much glutamate leads to excessive depolarisation of neurons. The long-term opening of NMDA receptors leads to excessive Ca2+ entering = damage to neurons
15
EPSPs and IPSPs work together TRUE/FALSE?
FALSE they work independently
16
axodentritic synapse
where the axon of one neuron communicates with the dentrite of another via chemical synapses
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indirect gating of ion channels (characteristics and features)
- transmitter binds to G-protein coupled receptor or metabotropic receptors
-activates biochemical pathway, eventually opening pore
- slower onset
- longer-lasting
18
where would you find Pyramidal cells and what do they look like?
cerebral cortex of the brain. Pyramid shape
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NPY
a neuropeptide
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2 forms of synapses
1. chemical synapse
2. electrical synapse
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IPSPs + EPSPs
cancel out
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spatial summation
synapse activation occurs at the same time at many different synapses and the EPSPs add together
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small molecule neurotransmitters include:
- Amino acids (glutamate, GABA, glycine)
- Acetylcholine (ACh)
- Amines (serotonin, dopamine, noradrenaline)
- others include ATP and Nitric oxide
24
inhibitory synapses cause a ________ of the post-synaptic membrane. The neurotransmitters involved are mainly ______ and ________ . Their ionic mechanism is the opening of the ion channels for __ and __ .
inhibitory synapses cause a _hyperpolarisation_ of the post-synaptic membrane. The neurotransmitters involved are mainly _GABA_ and _glycine_ . Their ionic mechanism is the opening of the ion channels for _K+_ and _Cl-_ .
25
through which type of cell junction are electrical synapses transmitted?
gap junction
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where would you find Purkinje cells?
in the cerebellum
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what are the two main chemical synapses in the CNS?
1. excitatory synapses (EPSPs)
2. inhibitory synapses (IPSPs)
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excitatory synapses cause a ________ of the post-synaptic membrane. The neurotransmitters involved are mainly ________ _____ and ________ . Their ionic mechanism is the transient opening of the ion channels for __ and __ and sometimes __.
excitatory synapses cause a _depolarisation_ of the post-synaptic membrane. The neurotransmitters involved are mainly _glutamic_ _acid_(glutamate)_ and _Acetylcholine_(ACH)_ . Their ionic mechanism is the transient opening of the ion channels for _K+_ and _Na+_ and sometimes _Ca2+_.
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features of neuropeptides
- Large molecules
- indirectly act on postsynatptic membrane
- slow and more dififfuse action
30
3 mechanisms of neurotransmitter inactivation
1. diffusion - away from the synaptic cleft
2. enzymatic degradation - e.g. ACH degraded by acetylcholinesterase
3. Re-uptake - neurotransmitter transporters take them away
31
_______ ________ arrives at the _________ terminal. The voltage-gated ___ channels open and there is a rapid influx of ___. _______ containing neurotransmitter move to the _________ membrane and fuse. The neurotransmitter ______ across the ______ ____ and binds to the ___________ receptors. Synaptic channels open. Postsynaptic _______ _________ is created.
_action_ _potential_ arrives at the _presynaptic_ terminal. The voltage-gated _Ca2+_ channels open and there is a rapid influx of _Ca2+_. _Vesicles_ containing neurotransmitter move to the _presynaptic_ membrane and fuse. The neurotransmitter _diffuses_ across the _synaptic_ _cleft_ and binds to the _postsynaptic_ receptors. Synaptic channels open. Postsynaptic _action_ _potential_ is created.
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NMDA
a directly gated glutamate receptor
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temporal summation
the higher the frequency of the synapse activation, from 1 synapse, the EPSPs can sum to reach threshold
34
end-plate potential due to ?
EPSP - therefore, increased permeability of (non-selective) ion channels to Na+ and K+ in the postsynaptic membrane
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_______ synapse are used almost entirely in the brain
chemical
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synaptic plasticity =
- process of weakening or strengthening synaptic transmission.
- Important in learning and memory.
- LTP (long-term potentiation) or LTD (long-term depression)
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synaptic delay =
time between arrival of AP at presynaptic knob to AP regeneration in the postsynaptic knob. Aproximately = 0.5ms
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3 key features of chemical synapses
1. specificity - specific neurotransmitters have specific effects
2. complexity - type, time, strength, etc.
3. plasticity - changes in synaptic structure and function
39
is end-plate potential supra- or sub- threshold
ALWAYS suprathreshold and ALWAYS triggers an AP
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