MR S10 - Incomplete

Question 1

Describe the storage of ACh

Answer 1

Actively packaged into high concentration (>100mM) vesicles at cholinergic terminals

Question 2

Describe the termination of ACh

Answer 2

Acetylcholine esterase degrades ACh to choline and acetate
In fast/nicotinic synapses, the enzyme is faster so half life of ACh is only a few milliseconds
A choline channel on the terminal of the synapse recaptures most choline

Question 3

Describe the synthesis of noradrenaline

Answer 3

Tyrosine is converted to DOPA by tyrosine hydroxylase (which is the rate-limiting step)
DOPA is converted to dopamine by aromatic amino acid decarboxylase (which is then packaged in a vesicle)
Dopamine is converted to noradrenaline by dopamine β hydroxylase (this occurs within the vesicle)

Question 4

Describe the packaging of noradrenaline

Answer 4

Active transport required to package dopamine into a vesicle, where it is converted to NA
High-concentration vesicle (0.5-1.0M)

Question 5

Describe the termination of noradrenaline

Answer 5

Uptake 1 is a high affinity reuptake system which removes NA from the synaptic cleft into cells
Uptake 2 is a widespread, lower affinity reuptake system which removes NA from the extracellular space
Cytoplasmic NA may be broken down by mono amine oxidase (MOA)

Question 6

Describe the synthesis of ACh

Answer 6

ACh is synthesised from acetyl CoA and choline by the enzyme choline acetyltransferase in the cytoplasm of cholinergic terminals