Lecture 5 - AP Propagation + Synaptic Transmission

Question 1

Why can the AP only propagate in 1 direction?

Answer 1

the sodium channels to the right are inactive (refractory period) and cannot open, while the ones on the left are closed but can be opened allowing another AP to occur

Question 2

True/False: Charge decays exponentially as we get further from insertion point

Answer 2

true

Question 3

Where do AP’s occur?

Answer 3

At the nodes of ranvier

Question 4

What is saltatory conduction?

Answer 4

Jumping of an AP down the axon (since AP’s only occur at nodes of ranvier)

Question 5

Where are the Na+ and K+ voltage gated channels?

Answer 5

At the nodes of ranvier

Question 6

How many neurotransmitters can a neuron send?

Answer 6

one

Question 7

How many neurotransmitters can a neuron receive?

Answer 7

Any number!

Question 8

Explain the steps of synaptic transmission:

Answer 8

1. transmitter synthesized and stored in vesicles
2. AP invades presynaptic terminal
3. Depolarization of presynaptic terminal caused voltage gated Calcium channels to open
4. Influx of calcium
5. calcium causes vesicles to fuse with presynaptic membrane
6. transmitter is released into synaptic cleft via exocytosis (diffuses across)
7. transmitter binds to receptor molecules in postsynaptic membrane
8. opening or closing of postsynaptic channels
9. postsynaptic current causes excitatory or inhibitory postsynaptic potential that changes the excitability of the postsynaptic cell
10. removal of neurotransmitter by glial cells or enzymatic degradation
11. retrieval of vesicular membrane from plasma membrane

Question 9

What does Calcium entering the presynaptic terminal cause?

Answer 9

the release of neurotransmitters

Question 10

What are dendritic spines?

Answer 10

Small projections of the cell membrane on the post-synaptic neuron that are the contact points

Question 11

What is a quanta?

Answer 11

The amount of NT in each vesicle

Question 12

What does the SNARE complex do?

Answer 12

facilitates the Binding + release of vesicular contents

Question 13

Explain the budding process (recycling of synaptic vesicles):

Answer 13

1. synaptic vesicles fuse
2. coated pits and coated vesicles contain HRP
3. Endosome contains HRP
4. Synaptic vesicles contain HRP

Question 14

What activates the SNARE complex?

Answer 14

Entry of Ca into the pre-synaptic terminal