CTB Nerve conduction and synapses

Question 1

What channels generate APs?

Answer 1

voltage gated Na and K channels

Question 2

Why don’t action potentials spread backward?

Answer 2

K+ channels are still open and hyperpolarizing the cells, and the Na channels are still inactivated

Question 3

2 types of synapses

Answer 3

electrical: gap junctions
chemical: NTs transferred over synaptic cleft

Question 4

Active zone and what are the main proteins present

Answer 4

presynaptic membrane area specialized for vesicle release; contains SNARE complexes

Question 5

Ca2+ is speculated to bind to ________ which increases the likelihood that the fusion of the vesicle membrane with the presynaptic membrane will occur

Answer 5

-Synaptotagmin

Question 6

Botulinum toxin mechanism

Answer 6

• blocks cholinergic vesicle release by blocking vesicle fusion process, exocytosis, and therefore, muscle contraction
• cleaves SNAP 25, the SNARE protein

Question 7

AChR

Answer 7

-pentameric
2 ACh molecules bind to channel to open gate
-Permeable to Na and K (ANIONS DO NOT PASS)
-leads to depolarization when open

Question 8

Opening of AChR channels creates an _________.

Answer 8

Endplate potential (EPP): large enough EPP to elicit an AP every time under physiological conditions- high safety factor

Question 9

High safety factor

Answer 9

• every presynaptic AP is associated with a postsynaptic AP

- EPP side is always way beyond the AP threshold

Question 10

EPP

Answer 10

• generator potential of local use only

- die out with distance away from endplate AChR channels