Flashcards in lecture 29 - Synaptic transmission Deck (40):
removes glutamate to presynaptic terminals and astrocytes. Other transporters take it to be stored in synaptic vesicles
what are the 2 classes of neurotransmitters?
- small molecule neurotransmitters ('classical')
- neuropeptides ('neuromodulators')
substance P and endorphins
synapse found in retina
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.
indirectly gated glutamate receptors
how are most amino acids inactivated?
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
Direct gating of ion channels (characteristics and features)
- transmitter binds directly to the ion channel complex and the pore opens
- very fast onset
neuromuscular junction =
chemical synaptic transmission between the axon terminals of motoneurons and the end-plates of muscle fibres
features of classical, small molecule neurotransmitters
fast action, acting directly
how small are the postsynaptic potentials?
directly gated glutamate receptors
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
EPSPs and IPSPs work together TRUE/FALSE?
FALSE they work independently
where the axon of one neuron communicates with the dentrite of another via chemical synapses
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
where would you find Pyramidal cells and what do they look like?
cerebral cortex of the brain. Pyramid shape
2 forms of synapses
1. chemical synapse
2. electrical synapse
IPSPs + EPSPs
synapse activation occurs at the same time at many different synapses and the EPSPs add together
small molecule neurotransmitters include:
- Amino acids (glutamate, GABA, glycine)
- Acetylcholine (ACh)
- Amines (serotonin, dopamine, noradrenaline)
- others include ATP and Nitric oxide
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-_ .
through which type of cell junction are electrical synapses transmitted?
where would you find Purkinje cells?
in the cerebellum
what are the two main chemical synapses in the CNS?
1. excitatory synapses (EPSPs)
2. inhibitory synapses (IPSPs)
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+_.
features of neuropeptides
- Large molecules
- indirectly act on postsynatptic membrane
- slow and more dififfuse action
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
_______ ________ 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.
a directly gated glutamate receptor
the higher the frequency of the synapse activation, from 1 synapse, the EPSPs can sum to reach threshold
end-plate potential due to ?
EPSP - therefore, increased permeability of (non-selective) ion channels to Na+ and K+ in the postsynaptic membrane
_______ synapse are used almost entirely in the brain
synaptic plasticity =
- process of weakening or strengthening synaptic transmission.
- Important in learning and memory.
- LTP (long-term potentiation) or LTD (long-term depression)
synaptic delay =
time between arrival of AP at presynaptic knob to AP regeneration in the postsynaptic knob. Aproximately = 0.5ms
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
is end-plate potential supra- or sub- threshold
ALWAYS suprathreshold and ALWAYS triggers an AP