Presynaptic mechanisms Dr. Chirwa

Question 1

What is the major form of communication within the nervous system?

Answer 1

Communication is done via SYNAPSES

Question 2

How does a synapses work?

Answer 2

Communication signals are transmitted from the upstream neuron (presynaptic) to the downstream (postsynaptic) neuron

Question 3

What is the functional contact between neurons?

Answer 3

Synapses

Question 4

What are the two types of neurons?

Answer 4

Electrical and chemical

Question 5

How does an electrical synapses work?

Answer 5

Current will flow through gap junctions (membrane channels that connect two cells together)

Question 6

How does a chemical synapses work?

Answer 6

Neurotransmitters (chemical) are released to enable cell-to-cell communication.

Question 7

What do gap junctions contain?

Answer 7

-Hexameric complexes formed by subunits (connexons channels)
-Connexons contain the integral protein connexin
- Connexons will provide the path pr “channel” to allow current to flow through

Question 8

How does the postsynaptic neuron become depolarized?

Answer 8

From action potential in presynaptic neurons

Question 9

Is there direct or indirect current flow for chemical synapses?

Answer 9

Indirect flow. There will be no direct flow for chemical synapses due to there being no intercellular continuity

Question 10

What is the purpose of synapsin?

Answer 10

Synapsin will keep the vesicles (neurotransmitters) held together until a single vesicles is ready for the docking process

Question 11

What is the docking process of a vesicle?

Answer 11

Docking process: The synapsin that’s holding the vesicle’s together will release 1 vesicle at a time. Once the vesicle is free, it will dock closer to the plasma lamina to get ready to be released

Question 12

What happens after the vesicle has docked?

Answer 12

Ca2+ will enter the cell and signal for the vesicle to be released from the docking stage. The vesicle will then travel to the postsynaptic neuron to release the intended neurotransmitter.

Question 13

What is the purpose of Clathrin?

Answer 13

Clathrin will help close the entry/exit point from where the Ca2+ and vesicle entered/exit by ENDOCYTOSIS

Question 14

Purpose of Synaptobrevin?

Answer 14

To hold and bring the vesicle closer to the plasma lamina membrane.

Question 15

Purpose of SNAP-25?

Answer 15

To hold Synaptobrevin and Syntaxin together while they work together to bring the vesicle closer to the membrane

Question 16

Purpose of Syntaxin?

Answer 16

To attach to the plasma membrane lamina while holding onto Synaptobrevin

Question 17

Purpose of Synaptotagmin?

Answer 17

Synaptotagmin is a signal for Ca2+ to be released into the membrane. Ca2+ will bind to synaptotagmin . The vesicle will be released after this last signal (neurotransmitter will be released to the postsynaptic)

Question 18

SNARE proteins:

Answer 18

Syntaxin
Synaptobrevin
SNAP-25
Synaptotagmin

Question 19

What will toxins from Clostridial toxins do?

Answer 19

Toxins will cleave SNARE proteins resulting leading to inhibiting transmitters

Question 20

What will BOTULINUM toxin block?

Answer 20

the release of excitatory Acetylcholine at the NMJ

Question 21

What does TETANUS toxin block?

Answer 21

the release of inhibitory transmitters Glycine and GABA

Question 22

What causes paralysis of neuromuscular synapses and skeletal muscle weakness?

Answer 22

Botulinum toxin blocking the release of ACH

Question 23

How long does it take for a vesicle to be recycled to be reused?

Answer 23

1min

Question 24

Lambert-Eaton Myasthenic syndrome:

Answer 24

antibodies will bind to Ca2+ channels and disrupt neuromuscular transmission

Question 25

What is the criteria for identifying as a neurotransmitter?

Answer 25

Must include: Synthesis Storage Release Mimicry Inactivation

Question 26

What are the two types of neurotransmitters?

Answer 26

Small molecule transmitters Peptide transmitters

Question 27

Where are small molecule transmitters made?

Answer 27

At the terminal region of the axon

Question 28

Where are the enzymes made for small molecule transmitters?

Answer 28

Inside of the SOMA (cell body).

Question 29

How are the small molecule transmitter enzymes made?

Answer 29

From slow anterograde transport (0.5-5mm/day). Not dependent on microtubules or ATPase motor molecules

Question 30

Where are the peptide transmitters and enzymes synthesis at?

Answer 30

SOMA (cell body)

Question 31

What are the peptide transmitters transported by ?

Answer 31

Fast anterograde transport (100-400 mm/day). Dependent on Kinesin (ATPase). Will be stored at the synaptic region until ready for transport

Question 32

T/F: Vesicle can contain more than 1 type of transmitter?

Answer 32

True

Question 33

How is Glutamate terminated?

Answer 33

By the uptake of glial cells via transporters. Glutamate will then be converted into glutamine. Glutamine is then taken up nerve terminals and converted back into glutamate

Question 33

What is the predominant precursor for GABA?

Answer 33

Glucose. Pyruvate and glutamine can also act as GABA precursors

Question 34

What does Acetylcholine serve as?

Answer 34

The neurotransmitter at the neuromuscular junction