Physiology 1.9

Question 1

What are electrical synapses?

Answer 1

• gap junctions
• fast
• bidirectional
• connects large groups of neurons
• cardiac muscle (some smooth)
• large and unselective (metabolic signals can be passed)

Question 2

What are chemical synapses?

Answer 2

synapses which release neurotransmitters

Question 3

What is the advantage of electrical synapses?

Answer 3

wide-spread coordinated contraction, such as with the heart

Question 4

What is the advantage of chemical synapses?

Answer 4

specificity for targeted neuron firing

Question 5

How does calcium affect the release of ACh?

Answer 5

Ca2+ controls vesicle fusion and mobilization of synaptic vesicles

Question 6

What are the 3 steps of transmitter release?

Answer 6

1) Targeting
2) Discharge of transmitter by exocytosis
3) Recycling of membrane

Question 7

What is the function of synapsin?

Answer 7

• Substrates for cAMP-dependent protein kinase and Ca2+/calmodulin-dependent protein kinase
• non-phos: bind the vesicles to actin filaments in the cytosol
• phos: release the vesicles, allowing them to move into the active zone

Question 8

What is the function of Rab?

Answer 8

• binds GTP
• hydrolysis of GTP helps target vesicle to docking site
• during exocytosis, Rab are recycled into cytoplasm

Question 9

What is the function of the SNARE complex?

Answer 9

• Vesicle proteins (Synaptobrevin (VAMP)) interact with membrane proteins (SNAP-25 and syntaxin) to dock the vesicle to the presynaptic membrane
• Munc18 binds to syntaxin before VAMP binds to allow exocytosis of synaptic vesicles

Question 10

What is the function of clostridial neurotoxins?

Answer 10

-cleave SNARE proteins and prevent vesicle fusion

Question 11

How does tetanus work in the body?

Answer 11

targets and cleaves VAMP

Question 12

How does botulinum work in the body?

Answer 12

cleave SNAP-25, VAMP, and syntaxin

Question 13

What is alpha-latrotoxin?

Answer 13

• spider toxin

- binds to neurexin (~syntaxin) to generate massive vesicle depletion and NT release

Question 14

What is the function of synaptotagmin?

Answer 14

• binds with Ca2+ in presynaptic terminal

- triggers fusion with terminal membrane and NT release for FAST synaptic transmission

Question 15

What are the criteria for neurotransmitters?

Answer 15

1) Synthesized in neuron
2) Present in presynaptic + released to affect postsynaptic/effector organ.
3) behaves same exogenously and endogenously.
4) specific way it is removed from the synaptic cleft

Question 16

What are the types of uptake transporters?

Answer 16

1) glutamate
- Na+/K+ exchange
- no Cl- dependence

2) NT
- Na+ and Cl- cotransport

Question 17

What are the uptake transporters for getting NTs into synaptic vesicles from cytoplasm?

Answer 17

• VMAT1/VMAT2: monoamines (dopamine, NE)
• VGAT: GABA
• VAChT: ACh

Question 18

What powers the vesicle transporters during neurotransmitter uptake?

Answer 18

H+ gradient