Jorgensen Specific Values Flashcards
Size limit of cytoplasmic coupling
< 1000 Da
Da size of Calcium ions
40 Da
Da size of NT
~150 Da
Da size of GFP
27 kDA, 2.5 nm
speed of action potential in myelinated axon
150 mm / ms
speed of action potential in unmyelinated axon
10 mm / ms
length (in time) of synaptic delay
0.5 - 3.0 ms
(1 ms)
velocity of action potential
~ 25 mm / ms
(60 mph)
width (in time) of AP
1 ms
range in widths of AP
100 us - 1 ms
how long does it take NTs to diffuse across synaptic cleft?
1 us
distance of synaptic cleft?
20 nm
amount of time it would take NTs to diffuse across 1 mm axon?
30 mins
[Na_in]
5 - 20 mM
(10 mM)
[Na_ex]
130-160 mM
(140 mM)
[K_in]
130-160 mM
(140 mM)
[K_ex]
4-8 mM
(5 mM)
[Ca_in]
.05 - 1 uM
(50nM)
[Ca_ex]
1.2-4 mM
(2mM)
length of synaptic delay
.5 - 3 ms
1 ms
how long does vesicle fusion take?
150 us
how long does diffusion across synaptic cleft take?
1-5 us
(cleft 20-50 nm)
how long does it take LGIC to open?
150 us
[calcium] required for NT release?
~ 25 uM
length of synaptic bouton
1 um
width of KcsA potassium channel
20 nm
size of single protein
5 nm
300 AA
size of protein complex
~12 nm
distance across plasma membrane
4 nm
Electrical Synapse Summary
- direct coupling of cytoplasm (electrically-coupled, dye-coupled)
- attenuates signal (100 mV action potential can be reduced to 1 mV current)
- often short duration, (~width AP; linked to memb potential timecourse)
- mimic the ionic conditions of the cell (excitatory or inhibitory)
- bidirectional information flow (but some are rectifiyng),
- some gated (for example, by changes in calcium, pH, lipid composition)
- generally not plastic or modifiable
quantal content equation
evoked responses / mini size = #SV/AP = quantal content
NSF
N-ethylmaleimide sensitive factor. Named because the activity is blocked by the drug. eventually separates the SNARES
SNAPs (a,b)
soluble NSF attachment proteins. Named based on discovery method (binds to NSF)
SNARE
SNAP receptor. Named based on discovery of binding NSF via a/b SNAP
V-SNARE
vesicle SNARE (R-SNARE). Transmembrane protein in the vesicle which confers specificity. Called ‘synaptobrevin’ or ‘VAMP’ at the synapse.
T-SNARE
target membrane SNARE (Q-SNARE). Transmembrane protein in the target membrane which confers specificity. Called ‘syntaxin’ and ‘SNAP-25) at the synapse
SNARE complex
ultra-stable trimeric complex composed of V-SNARE (synaptobrevin), T-SNAREs (syntaxin and SNAP-25)
about how long does it take calcium channels to open in the presynaptic neuron?
300 us
Kd for calcium
0.1 uM
Calcium channels model
Ca response to different APs
calcium influx (and hence neurotransmitter release) is determined by:
(1) calcium channel kinetics
Kinetics of open state Ca channels
i. slow activation kinetics
ii. high temperature sensitivity (Q10 = 6 to 12)
(2) by driving force for calcium
predicted reversal potential (2mM external 50 nM internal) = +130 mV reported reversal potential for calcium = +40-7 mV (not +130 mV)
i. low driving force at peak Vm of action potential
ii. high driving force as Vm repolarizes
calcium sensor
synaptotagmin
also required for fast vessicle fusion (accelerates but not essential)
