Chemical synapses

Question 1

Types of synapses and differences?

Answer 1

axodendritic - on dendrite
axoaxonic - on axon
axosomatic - on cell body
dendrodendritic 
neuromuscular junction - in between muscles

Question 2

What do synapses do?
convergence?
divergence?
allows processing that is 4 things...
defective neurotransmission? what happens

Answer 2

allow info to flow in different direction
convergence: allows lots of info from different inputs to be combined
divergence: can send out lots of info from different outputs
complex, elaborate, subtle, flexible
neurological and psychiatric disorders

Question 3

standard features of a chemical synapse?

Answer 3

axon with swelling = pre-synaptic component (contains vesicles)
synaptic cleft = 20-50nm gap
It’s an adhesive junction

Question 4

Variability in synapses?

Answer 4

can be different sizes, can grow/shrink
can move position on target cell
can have multiple active zones
can release neurotransmitter from more than one active zone

Question 5

Types of transmitter
Amino acids
Biogenic amines
Neuropeptides

Answer 5

aa- GABA, Glycine,Aspartic acid, Glutamic acid
b - epinephrine, norepinephrine, dopamine, serotonin, histamine
n - substance P, enkephalin, B-endorphin, cholecytokinin

Question 6

Synthesis and storage?
where are neuropeptides synthesised and stored?
What is synthesised and stored in terminals?

Answer 6

synthesised in soma, stored in secretory granules

ACh, amines, amino acid NETs (stored in vesicles)

Question 7

Chemical synaptic transmission
‘docked’?
mechanism to stop fusing with membrane?
What happens when Ca2+ channels open?

Answer 7

Some NETs are ‘docked’ at terminal membrane= ready for rapid release before AP
mechanism keeps vesicles away from membrane until AP arrives (when Ca2+ channels open= Ca2+ moves in and stimulates proteins to allow vesicles to fuse with membrane + release NETs via exocytosis)

Question 8

Quantal release?

Freeze- fracture technique

Answer 8

the effect of one vesicle releasing is approximate to any other (quanta)
FF technique = split a synapse to see inside

Question 9

2 main types of receptor?

Receptor-dependent action?

Answer 9

Ligand- gated ion channel (ionotropic)
G-protein coupled (metabotropic)
-ion-gated = permeable to Na+
G-coupled = activating K+channel

Question 10

Transmitter or Ligand-gated ion channels (ionotropic) characteristics?

Answer 10

fast acting
open transiently in response to NET binding = rapid onset of effect
(at fast excitatoy synapse = generates EPSP)
(at fast inhibitory synapse = generates IPSP)

Question 11

G-protein coupled receptors (metabotropic) characteristics?

Answer 11

transmission is slower and more complex
signal amplification
multiple channels may be affected
many of the recpetors act as modulators (rather than directly causing IPSPs and EPSPs)

Question 12

How does transmission terminate?

Answer 12

Enzyme breaks down NETs
OR
Reuptake occurs - diffusion out of synaptic cleft