Lect 2 - neuro excitation/inhibition/modulation Flashcards
what makes thing ex or in Glu GABA ACh ionotropic metatropic (34 cards)
differentiate between excitatory, inhibitory, and modulatory
excitatory - increase excitability of the cell
inhibitory - makes resting membrane less likely to depolarise
modulatory - indirectly change excitability of the pre or postsynaptic membrane without having direct effects
what is reversal potential, what’s its relationship to the quilibrium potential, does it differ between excite and inhib reps
reversal potential is the membrane potential at which there is no net movement of ions across the membrane
it is the same as the equilibrium potential
lower Erev mean that the membrane is capped at that voltage therefore if threshold is higher than it, the postsynaptic response is more likely to be an IPSP
which one is bigger, ESPS or EPP? what consequences does this have on ESPS
EPSP is much smaller, so EPSP must always be summed for it to have an effect. EPP are much larger and is fail-safe in that it will always have an excitory postsynpatic response
what is an example of excitatory NT
gluatmatergic, e.g. glutamate or aspartate
what is an example of modulatory NT
norepinephrine
how is modulatory synapse different to the other two
modulatory synapse doesn’t have direct effect on synapse, but makes them more or less sensitive
describe the typical characteristic of modualtory synapse, why do we need them
generally mediated by slower metatropic receptors (G-protein coupled receptors)
hence they are slower and last longer, they will undergo signal amplification.
there is also more potential and flexibility to vary excitability
what happens when K channels are closed
cells harder to depolarise, leading to greater excitablity
compare what happen in excitation vs inhibition in terms of ion channels openning
excitation: we dont want K to go, we dont want Cl to come in
what is the presynaptic effect
reduced NT release or production
list some types of NTs, what are some differences between them
gases, amino acids, monamines, catcholamines, purines, lipid metabolites, peptides
amino acids and biogenic amines are small and fast acting
peptides are slower acting but have long term change
what are the 3 ways by which NT signals achieve its effect
- ligand-gated (fastest, 1 bound receptor = 1 open channel)
- amplification by membrane pathway aka G-protein
- amplification by signally cascade, longer term change
(e. g. bound receptor -> alpha-subunits -> make many cAMPs -> protein -> protein kinase opens heaps of channels)
what are examples of inotropic receptors
a
differentiate between ionotropic and metatropic
a
describe the glutamate cycle
a
what are the 3 main ionotropic glutamate receptors
a
why is there a delay in repolarization with NMDA receptors
a
what are the types of metabotropic glutamate receptors
a
describe the typical exitatory synpase
most of them use glutamatergic
opens non-selective Na/K ion channels (fast)
increase excitabiliyt of membrane
describe the typical inhibitory synpase
most use GABAergic or glycinergic, e.g. GABA or glycine
also mediated by fast ionotropic receptors
IPSP by opening Cl channels - negative keeps the cell polarised, they keep membrane voltage away from potential threshold
in reality, the excitability of most neurons is determined by the balance of excitory and inhibitory
what are the two types of excitatory synapses?
glutamatergic - glutamate
cholinergic - ACh
why is glutamate controlled, and how is it controlled
highly toxic, controlled via uptake, using e.g. astrocytes
EAAT transports glutamate to either glial cells, where it is made into glutamine, or back into the presynaptic terminal for reuse
what are the 3 ionotropic glutamate receptors, and what are their characteristics
- AMPA - for fast stuff
- NMDA - synaptic plasticity (therefore need to be slow)
- Kainate - regulates release of GABA
compare AMPA with NMDA
AMPA - nice and fast, open even with negative membrane potential
NMDA - slower acting, opens when Vm is more positive (because of Mg plug). this brings in Ca which signals long term change
NMDA is like a coincidence detector, important for plasticity and developent
