Synaptic transmission Lec06 Flashcards
EPSPs increase the probability for an action potential to be generated because they let _____ into the cell body depolarizing the cell.
sodium
IPSPs decrease the probability for AP by
letting K out or chlorine in
direction of electrical synapses
bidirectional
electrical synapses are connected via
gap junctions (made of connexins)
what kind of pores do electrical synapses have? what do they let in
very large pores for unselective ion diffusion
what triggers vesicle fusion?
influx of ca through voltage gated ca channels
what happens if you have no Ca voltage gated channels
no NT release
what happens if you ↓ external [Ca]
↓ # of vesicles = ↓ postsynaptic potential
Ionotropic receptors - ligand-gated ion channels respond in ____
msec
Metabotropic receptors - G-protein-linked receptors that respond in ___
sec/min (growth factor recpeotrs take even longer)
how does inactivation of chemical nt take place
via reuptake, glial uptake, diffusion, or enzymatic breakdown
what are the advantages of chemical synapses
directionality, amplification, plasticity, summation
what is facilitation
short-term synaptic plasticity
what does facilitation involve? what does it result in?
multiple action potentials in a short time (<50 msec) = ↑↑ in synaptic strength
describe the 2nd epsp after facilitation
2nd EPSP larger than the 1st because Ca clearance is slower than Ca entry into cell
how large are small molecule nt
50 nm diameter
how are small molecule NT stored?
in clear vesicles
some ___ are docked at active zones
small molecule nt
docked small molecule nt are released by
local ca influx
how are neuropeptides stored?
dense core vesicles
what is required for neuropeptide release?
high frequency stimulation
Vesicle release is quantal/discrete: each vesicle =
1 mini end plate potential
how do miniend plate potentials cause depolarization?
Many MEPPs make up the endplate potential, EPP, causing depolarization
how can you get larger mini end plate potentials?
more ach or more veiscles
cable theory
neuron changes in synapse potential decrease with time and space
___ and ___ determine probability of an action potential due to leakage
Temporal and spatial summation
EPSP & IPSP amplitude & direction depend on
ion permeability and membrane voltage
NMDA is slower, Mg-blocked, but allows ___
Ca entry
GABA__ receptors are ligand-gated channels
A
GABA A receptors make __ with CL- ions
fast ipsp
GABA A receptors have ___ subunits
5
what increases the GABA A channel open time
a barbituate + gaba (increases the channel open time)
GABA __ receptor are g protein linked and slower
B
how many synapses does each neuron integrate ifnormation from?
multiple
what are the 4 criteria for chemical NTs?
1) present in presynaptic terminal.
2) released in response to stimulation – release must be Ca2+ dependent.
3) specific receptors for the neurotransmitter must be present on the postsynaptic cell.
4) mechanism to inactivate neurotransmitter must be present (reuptake, enzymatic breakdown).
what type of flow occurs through gap junctions in electrical synapses
passive flow
how common are electrical synapses?
they are present in cns but less common than electrical synapses
brainstem neurons that regulate breathing are synchronized by
electrical synapses.
chemical syanspes provide potentiation for
- excitation and inhbiiton
- plasticity and remodeling
what drives Ca into the presynatpic membrane
concentration gradient (more ca outside)
electrical gradient
what does facilitation result from?
prolonged elevation of presynaptic Ca
Synaptic facilitation is a rapid increase in ___
synaptic strength
. Facilitation is not observed if __
two APs arrive far apart in time
how many chemical transmitters can a single neuron release?
many
what is the range of time courses of chemical transmitters?
msec to days
trnasport of neuropetide vesicles is dependent on ___
ATP
what is the postsynaptic density
an electron dense area with many receptors in the postsynaptic target cell
The MEPPs result from the discharge of the contents of
a single synaptic vesicle
post synaptic potentials resutl from
conductance changes to
synaptic potentials are passive events that become progressively smaller at
greater distances ro
why dont dendrites transmit AP?
- they do not contain many Na+ channels
- their thresholds for excitation are too high.
what does capable theory take into account
- membrane capacitance
- embrane resistance
- longitudinal cytoplasmic resistance between different parts of the neuron
glutamate binding to ampa and nmda exhibits distinct
- kinetics
- pharmacologic sensitivites
- target cell effects
interposition of a ____ in a neuronal circuit can prevent overactity in the cns
inhbiitior synapse
