Chapter 12 Flashcards
How did they determine if Na+ was important for NT release
Using tetrodotoxin
Where is tertodotoxin from
Pufferfish
What does tetrodotoxin do
Blocks voltage gated Na+ channels
When you eat pufferfish what happens to your tongue
It goes numb
Is Na+ important for NT release and why
No, because blocking Na+ voltage gated channels had no effect on the transmission of an impulse
How did they determine if K+ was important for NT release
Using tetraethylammonium (TEA)
What does terteethylammonium do
Blocks voltage gated K+ channels
IS K+ important for NT release and why
No, because blocking K+ voltage gated channels had no effect on the transmission of an impulse
What happens when both Na+ and K+ cause more blocked
We see that more depolarization leads to more NT release
True or False:
There is a high number of Ca++ channels at the terminal button
True
How does blocking both Na+ and K+ more NT release
The presynaptic cell is depolarized causing Ca++ to enter the terminal button which causes an increased amount f NT release
What opens the Ca++ voltage gated channels
Depolarization of the terminal button (presynpatic cell)
Where are presynaptic Ca++ channels concentrated in the terminal button
The active zone
Where are the active zones of the terminal button located
Directly across from postsynaptic receptors
What is the active zone
The place NT is released
Do Ca++ channels open quickly or slowly
Slowly
What happens as soon as Ca++ channels open
NT is released
What does NT being released as soon as Ca++ channels opens mean
Indicates that NT is primed and ready to be released
What are the 2 types of voltage gated Ca++ channels
- High voltage activated Ca++ channels
2. Low voltage activated Ca++ channels
What type of Ca++ channels are more common
High voltage activated Ca++ channels
What are low voltage activated Ca++ channels important for
Things that require tonic firing
Where are low voltage activated Ca++ channels located
Pacemaker firing in the heart
How does Ca++ cause the release of NT
Activates vesicles to exocytosis NT into synaptic cleft
Where are the vesicles located
The active zone
True or False:
Some vesicles are docked at the active zone
True
How are active zones oriented
Linear at the NMJ
What are the shapes of the active zones
Disc shaped at central synapses
What are the parallel rows of particles thought to be
Voltage gated Ca++ channels
What is the vesicle membrane made of
Phospholipid bilayer
What are the divots, pockets, or big dots
Vesicles that fused with the membrane
What are the 2 types of vesicle fusion
- Reversible fusion pore
2. Clathrin mediated
What are the 2 type of reversible fusion pore
- Kiss method
2. Low stimulation
What is the type of clathrin mediated
Sustained stimulation
What is the vesicle attached to the membrane by in reversible fusion pore
By a stalk
Are the vesicles open for a long time or short period of time in reversible fusion pore
Short period of time
What are the 2 types of the kiss method
- Kiss and stay
2. Kiss and run
What is kiss and stay
Vesicle stays docked after NT release
What is the kiss and run method
Vesicle moves to a vesicle pool after NT release
What happens to the vesicle in clathrin mediated fusion
The vesicle fuses with the plasma membrane
What shape does the vesicle make when it is fusing with the plasma membrane
Omega shaped and eventually flattens out
What is the vesicle membrane coated in during clathrin mediated fusion
Clathrin
What does clathrin look like on the outside of a vesicle
A bunch of dots around the vesicle
What does the clathrin help with
Helps the vesicle be taken back into the terminal button via endocytosis
What can happen to the vesicle after it has been endocytosised
It can be reused or recycled
What happens once the vesicle is taken back into the terminal button
The clathrin is removed and the vesicle is either filled again (reused) or goes and is stored in the endosome (recycled)
The kiss and stay method would be like doing what in basketball
Standing in one spot and dribbling the ball
The kiss and run method would be like doing what in basketball
Moving and dribbling the ball
What happens once the vesicle fuses with the membrane
The NT is released into the synapse via exocytosis
What are the steps of vesicle fusion (3)
- The action potential reaches the terminal button
- Voltage gated Ca++ channels open
- Vesicles fuse to the membrane
What does the pool of vesicles at the active zone allow for
Large NT release occurs when AP reaches the terminal button
What protein is important for vesicles docking at the active zone
Synapsin
What does synapsin bind to
Vesicles and cytoskeleton
What does synapsin prevent
The vesicle from binding to the cell membrane
What happens to the synapsin when the terminal button is depolarized
It is phosphorylated
What does phosphorylation of synapsin cause
Vesicle to be released from actin allowing it to bind to the membrane
What are the 2 proteins involved in vesicle fusion
- V-snare
2. T-snare
What is V-snare
Vesicle membrane associated proteins
What is T-snare
Cell membrane associated proteins
What is the name of the V-snare protein
Synaptobrevin
What are the names of the 2 T-snare proteins
- Syntaxin
2. SNAP-25
What does synaptobrevin do
Forms a tight complex with syntaxin and SNAP-25
What are synaptobrevin, syntaxin, and SNAP-25 bound by
Munc 18
What protein is important for calcium mediation
Synaptotagmin
Is synaptotagmin associated with the vesicle or cell membrane
Vesicle
What is synaptotagmin attached to
Snare proteins
What does synaptotagmin act like
A switch
What does synaptotagmin do
Binds Ca++ which activates synpatotagmin resulting in a conformational change in proteins causing the vesicle to touch the membrane leading to fusion of the vesicle and NT release
How many Ca++ bind to synaptotagmin
5 Ca++
Protein Review:
What is synapsin important for and what does it do
Important for vesicle docking and it binds to actin associated with the vesicle
Protein Review:
What type of protein is synaptobrevin and what is it’s association
V-snare protein and associated with the vesicle
Protein Review:
What type of protein is syntaxin and what is it’s association and what does bind to
T-snare protein and associated with the cell membrane and binds to synaptobrevin
Protein Review:
What type of protein is SNAP-25 and what is it’s association and what does bind to
T-snare protein and associated with the cell membrane and binds to synaptobrevin
Protein Review:
What does Munc 18 do
Binds with V and T snares keeping them together
Protein Review:
What is synaptotagmin attached to and what does it bind
Attached to the vesicle and binds Ca++
What are the steps of activity in a chemical synapse (5)
- The action potential reaches the terminal
- Voltage gated Ca++ channels open
- Vesicles fuse to the membrane
- Contents of the vesicles diffuse to the postsynaptic receptor
- Binding of ligand to receptors affects postsynaptic cell
When does the clathrin coating occur
When the vesicle undergoes endocytosis
What ion is king in the terminal button
Ca++
What is it called when synaptic strength can be modified
Synaptic plasticity
What is tetanus
Rapid stimulation or depolarization of the presynaptic cell
What does tetanus lead to
Long term potentiation (LTP)
What is long term potentiation
A persistent strengthening of synapses that can last for several days
What is an EPSP
Response in the postsynaptic cell is larger after tetanus
True or False:
Synaptic strength can be modified through pre or postsynaptic mechanisms
True
What are the 2 ways you can modify synaptic strength in the presynaptic cell
- Effect of Ca++ influx
2. Effect of NT amount
How does Ca++ influx modify synaptic strength in the presynaptic cell
Increases the amount of Ca++ in the terminal button which increase the amount of active vesicles which increases the amount of NT released
How does NT amount modify synaptic strength in the presynaptic cell
More NT in terminal button means more NT can be released into the synaptic cleft
What causes long term depression (LTD)
The tetanus being spread out
