Synapses Flashcards
What is the function of synapses?
For neurons to pass information to other neurons or muscles.
Allow information processing as well as transmission
What is the post synaptic response called?
Post synaptic potential (PSP)
What was the model synapse?
Frog neuromuscular synapse
What is the evidence for chemically gated synapse? (Most synapses)
Physical gap
Applying a particular chemical to post synaptic site causes a response
Vesicles in pre synaptic terminals contain same chemical that causes the psp
What type of synapse is best at decision making?
Chemical
What happens first when presynaptic terminal is excited?
Voltage gated Ca++ in presynaptic terminal membrane open, Ca++ floods in, very strong electrochemical gradient
Where was the evidence for neurotransmitter release found?
Squid giant synapse
How do we know Ca++ enters?
Llinas and Nicholson
Injected protein that glows blue in presence of Ca++
Light emitted measures proportional to PSP size
Where does delay in synaptic transmission come from?
Mostly for Ca++ channels to open
What does influx of Ca++ cause?
A series of enzyme like events that cause vesicles to fuse with presynaptic membrane and release neurotransmitter into the cleft
What do neurotransmitters do
Some bind to receptor sites, causing chemically gated channels to open (or close in a few cases)
What ion enters post synaptic terminal after neurotransmitter binds?
Na+
Give an example of a neurotransmitter
Acetyl Choline (ACh)
What is the evidence for neurotransmitters causing psps
Direct measure of current flow through a single post synaptic channel - Neher and Sakmann 1991
Compare spike with psp
Spike: Voltage gated channels 1/10 V Discrete fixed amplitude Travel by propagation PSP: Chemically gated channels Few mV Adds with our psps Cannot travel far
