Adrenergic system

Question 1

How is noradrenaline synthesized?

Answer 1

1. Phenylalanine is hydroxylated into tyrosine.
2. Tyrosine is hydroxylated into DOPA.
3. DOPA is decarboxylated into Dopamine.
4. Dopamine is hydroxylated into noradrenaline.

Question 2

Where is noradrenaline synthesized in the neuron pathway?

Answer 2

Pre-ganglionic neurone

Question 3

Which receptor causes vesicles to stop releasing noradrenaline once binded to?

Answer 3

alpha 2 receptor

Question 4

Which transporter transports noradrenaline into non-neuronal effector cells?

Answer 4

Extraneuronal monoamine transporter (EMT)

Question 5

How much of noradrenaline is uptaken by non-neuronal cells?

Answer 5

25%

Question 6

What metabolises noradrenaline?

Answer 6

monoamine oxidase and catechol-O-methyl transferase

MAO is found on the surface membrane of mitochondria [intracellular

Question 7

How much noradrenaline is re-packaged into vesicles?

Answer 7

75%

Question 8

G-protein cycle

ACTIVATION-DEACTIVATION

Answer 8

1. G-protein binds to GPRC
2. GDP on a-subunit is exchanged for a GTP [ACTIVATES]
3. α-subunit acts as a GTPase and breakdowns GTP to GDP to DE-ACTIVATE the protein.

Question 9

GEFs

Answer 9

Guanine nucleotide Exchange Factor

They speed up the activation of G-protein.

Question 10

GAPs

Answer 10

GTPase-activating protein

They accelerate the hydrolysis of the GTP to GDP to DE-ACTIVATE the G-protein.

Question 11

GAi

Answer 11

An α-subunit that inhibits adenyl cyclase - decreases cAMP

Question 12

GAs

Answer 12

A stimulatory α-subunit that ACTIVATES adenylate cyclase

Question 13

G_βγ

Answer 13

An effector subunit that binds to and activates other proteins

IMPORTANT EXAMPLE: Phospholipase C

Question 14

MAO

Answer 14

Monoamine oxidase

Question 15

COMT

Answer 15

Catechol O-methyl transferase

Question 16

β2 adrenoreceptor agonist

Answer 16

Relax the smooth muscle in the airway.

Used as bronchodilators in medicine.

Question 17

α2 adrenoreceptor

Answer 17

Inhibits vesicle release of noredrenaline.

Activates the Gi protein that inhibits adenyl cyclase and therefore REDUCES levels of cAMP. This is turn results in lower PKA which inactivates the Calcium channels.

Question 18

β adrenoreceptor

Answer 18

Noradrenaline binding stimulates adenylate cyclase. This increase cAMP levels and activates protein kinase A.

Result: calcium channels and plasma membrane open.