Synaptic Transmission Flashcards
Electrical synapses are formed by
Gap junctions
Proteins which form gap junctions
connexins
A connexon is formed by what
6 connexins which form large membrane channels
Adjacent connexons form what
a continuos pore-connects the cytoplasm of two cells
How gap junctions effect electrical potential
action potentials can move between cells
Action potentials stimulate an influx of what ion? How?
The depolarization opens Calcium channels
What does calcium do
increases vesicular fusion-thus allowing NT to be released from the cell
How NT travels between cells
diffuse across the very narrow synaptic cleft
How NT gets out of axon terminal
Vesicular fusion and exocytosis of NT containing vesicles
Docking of vesicle
when a vesicle is held close to the membrane by proteins (standing ready to be released)
Priming in AP
prepared and ready for release when the calcium comes into the synaptic cell
v-Snare Proteins (2)
Synaptobrevin and synaptotagmin
in vesicles
what binds Ca+ in vesicular fusion
Synaptotagmin- they then tighten up and you get full fusion (vesicle becomes part of the plasma membrane and its contents are dumped out)
t-snares (2)
Syntaxin and SNAP-25
in the target
Snare proteins are involved in what
vesicular fusion priming
Axodenritic
Axon synapses with a dendrite
Axospinous
Axon synapses to dendrite spine
Axosomatic
synapses directly on the cell body (soma)
Axoaxonic
Controls presynaptic modulation (release from terminal)- where axon meets the presynaptic terminal
-some inhibit some excite release of NT at synapses
Synaptic Potential
Graded potentials (variable amplitude)
Excitatory Synaptic potential
EPSP-Excitatory postsynaptic potential
increase the probability of firing of an AP
inhibitory postsynaptic potential
Decreases the likelihood of AP by hyper-polarizing-open a Cl or K channel (K goes out and hyperpolarizes)
Synaptic integration (neurons)
neurons integrate (combine) the number, Amplitude, rate of decay, and timing of EPSPs and IPSPs in deciding to fire AP
Spatial and Temporal
Temporal Summation
One synapse firing slowly but if it fires more rapidly the AP can summate and get larger (if another one gets there before the first one is done the result is larger than the second alone)-ALSO longer duration
Spatial summation
Two synapses separated by space collectively they cause a higher membrane potential
Summation of EPSPs and IPSPS
if the IPSP and EPSP are at the same or nearly the same time the IPSP can keep the EPSP from reaching threshold and thus stop the AP
Synaptic Plasticity and memory forming
strengthening or weakening of the synaptic efficacy which has been shown to last for days (9) in the lab (maybe years in vivo)
Forming a memory allows the spines to get bigger and make a synapse more effective and likely to fire
Axons can converge on other dendrites
..
Fast axonal transport
moves 400mm/day
vesicles move along microtubules
Slow Axonal Transport
1-2mm/day involving structural proteins such as microtubules and is rate limiting for recovery of axons from damage
Retrograde Transport
1/2 as fast as slow transport- from terminal to soma
Anterograde
soma to axon terminal
