Synapses

Question 1

Chemical Synapse

Answer 1

• Pre-synaptic cell releases neurotransmitters into the synaptic cleft
• Post-synaptic cell responds to neurotransmitter signal

Question 2

Diversity Of Synaptic Transmission

Answer 2

1. Electrical vs chemical synapse
2. Synapse structure
3. Synapse location
4. Signal conduction
   * ionotropic vs metabotropic

Question 3

Chemical Synapses Rely On Voltage - Gated Ca2+ Channels

Answer 3

• Open in the terminal in response to the action potential.
• Ca2+ moves into the cell and ultimately induces vesicle secretion.

Question 4

Exocytosis Of Vesicles

Answer 4

• Ca2+ dependent
• Synaptotagmin is a Ca 2+ sensor
• Activated synaptotagmin facilitates membrane fusion and formation of the SNARE complex
• Snare: SNAP receptor, snares, and snaps interact

Question 5

Myasthenia Gravis

Answer 5

• Autoimmune condition
• ACh receptors at the NMJ are destroyed
• Reduced ability of muscle to respond to nerve impulse
• Muscle fatigue and weakness

Question 6

Treating Myasthenia Gravis

Answer 6

• Acetylcholinesterase inhibitors
• Decreases ACh turnover (prolonging nerve signal) and increases muscle strength

Question 7

Cholinergic Synapses:
Any Synapse That Releases ACh

Answer 7

1. All neuromuscular junctions with skeletal muscle fibers
2. Many synapses in the CNS
3. All neuron-to-neuron synapses in PNS

Question 8

Synaptic Fatigue

Answer 8

when neurotransmitters cannot recycle fast enough to meet the demands of intense stimuli

Question 9

Production And Termination Of ACh In The Synapse

Answer 9

1) Acetyl CoA is synthesized by the mitochondria
2) Converted to ACh by choline acetyltransferase
3) Packaged for Exocytosis
4) Exocytosis
5) After release into the synapse, the ACh receptor on the post-synaptic cell
6) Acetylcholine esterase (AChE) breaks ACh into acetate and choline
7) The pre-synaptic cell recycles choline; acetate diffuses away.

Question 10

Key Players At Rest

Answer 10

• Synaptotagmin (Ca2+ sensor)
• v- and t-SNAREs:
  synaptobrevin (vesicular)
  syntaxin (membrane terminal) inhibited by Munc18)
• SNAP 25

Question 11

Vesicle In Primed Position: SNAREs And SNAPs Are Bound

Answer 11

SNARE complex includes:
* Synaptobrevin
* Syntaxin (now open, see change in
position of Munc18)
* SNAP-25
Synaptotagmin is not yet interacting with the SNARE complex
Complexin stabilizes the complex in the poised position

Question 12

Vesicle Fusion: The AP Causes Ca2+ Influx

Answer 12

• Ca2+ synaptotagmin complex binds to the snare complex.
• displaces complexing, destabilizing the complex.