Synaptic Transmission Flashcards
What are the two general ways in which cells communicate?
Electrical and Chemical Synapse
What is an electrical synapse?
Gap junctions that transfer ions from the cytoplasm of one cell to another
What is a chemical synapse?
The release of a chemical that diffuses to, and acts upon, another cell
Most significant electrical synapses in the human body?
Heart, Liver, Lens, and Myelin Sheath
Cell membranes are normally separated by _____. Gap junctions have cells separated by ____ __.
20nm
3.5 nm
Another name for a gap junction?
Connexon
What is a gap junction made of?
6 Connexins
The presynaptic cell must be lined up with
the postsynaptic connexon
What determines what can pass through a gap junction?
Pore Size
What conditions may cause gap-channels to close?
Lowered cytoplasmic pH or elevated Ca2+
For two non-coupled adjacent cells, depolarization will cause what in the other?
nothing
For two coupled adjacent cells, depolarization will cause what in the other?
Depolarization
Why might the hypothalamus require gap junctions? Cardiac muscle?
To ensure coordinated release/contraction amongst many cells
Relationship btw CMT and gap junctions?
Cells wrap around, connect layers with gap junctions to allow the deepest layers to get sustenance.
What is the major mechanism for the release of neurotransmitters?
Vesicular Secretion
Depolarization of the terminal membrane of axons causes what?
Opening of voltage gated Ca channels
Two proteins involved in priming synaptic vesicles for fusion.
NSF and SNAPs
What do NSF and SNAPs regulate?
Assembly of the SNARE complex
Name three SNARE proteins.
Synaptobrevin, syntaxin, and SNAP-25
SNARE protein responsible for Ca regulation?
Synaptotagmin
What does synaptotagmin do?
When Ca conc. is elevated, inserts into cell membrane, leading to fusion of membranes and release of contents
What are end plates?
Specialized sites where the presynaptic axon terminates on a muscle fiber
What is an end plate potential?
An AP in the presyn… neuron elicits a transient depolarization of the muscle fiber.
Very low Ca concentration will do what to EPPs?
Make them much smaller, but same shape
What are the much smaller waves (but same shape/pharm response) called?
Miniature End Plate Potentials
Increasing external Ca will do what to amplitude?
Nothing.
What does increasing external Ca do for muscle cells?
Decrease the number of failures, higher release probability
What is a quantum?
The amount of NT in a vesicle
How many molecules of AcCho are required to set off a MEPP
7000
Enzyme that inactivates acetylcholine? Products of this reaction??
Acetylcholinesterase
Choline and Acetyl CoA
Enzyme that reassembles acetylcholine?
acetyltransferase
After initial release, what two parts are recycled?
Cell membrane and choline
What is spatial integration?
Integration of multiple signals from different locations on a dendrite arriving at once
A larger lambda means….
less decay over length, greater chance for synaptic potentials to summate
What is temporal integration?
Integration of multiple inputs from the same axon occurring at different times.
A larger tau means…
less decay over time, greater chance of summation.
Define EPSP
Excitatory Post Synaptic Potential
Excitatory NT increase Na permeability
Review 4-11
That seemed important
Why are EPSPs tricky to navigate?
Because an EPSP changes the permeability of both Na and K, depending on the membrane voltage.
What equation can be used to determine which way EPSP values will go?
Em - Eion = X
Move toward Eion of the larger X
What are IPSPs? What do they do?
Inhibitory Post Synaptic Potential
Increase Cl- permeability at the postsynaptic membrane
Causes hyperpolatization, fewer APs
Aside from Cl-, what can cause hyperpolarization to occur?
Increased K permeability at the postsynaptic
How does level of depolarization influence IPSPs?
More depolarized cell will require a greater IPSP
Can IPSPs and EPSPs interact?
Yes
How does the brain code information?
Place codes
Intensity Coding
Recruitment
Input Organization
How does recruitment promote mapping?
Axons have a limited range. Increased axons will increase the dynamic range.
How does the CNS accomplis input organization?
Center surround fields maximize contrast
How do you treat myasthenia gravis?
Acetylcholinesterase Inhibitor
