Endo: Adrenal Medulla

Question 1

What cells make epi?

Answer 1

Chromaffin cells within the adrenal medulla make epi

Question 2

Describe the synthesis of Norepi

Answer 2

1. Within cytosol, Tyrosine is converted to DOPA
   
   • by Tyr hydroxylase
2. DOPA is converted to Dopamine
   
   • by DOPA decarboxylase
3. Dopamine is shuttled into vesicle by VMAT
4. Within vesicle, Dopamine is converted to Norepi
   
   • by Dopamine beta hydroxylase

Question 3

Describe the synthesis of epi from norepi

Answer 3

1. Norepi within vesicle is moved into cytosol by VMAT transporter
2. Norepi is converted into Epi
   
   • by PMNT
3. Epi is shuttled back into vesicle

Question 4

Describe the release of Epi using a Nicotinic receptor at the adrenal medulla

Answer 4

1. Splanchnic nerve releases ACh onto adrenal medulla
2. ACh binds nicotinic receptor
3. Nicotinic receptor opens, causing Na influx
4. Depolarization opens Ca channels
5. Ca influx causes exocytosis of vesicles with epi

Question 5

Describe the release of Epi using a Muscarinic receptor at the adrenal medulla

Answer 5

1. Splanchnic nerve releases ACh onto adrenal medulla
2. ACh binds Gq receptor
3. G protein activation -> PLC -> Production of IP3 and DAG -> release of intracellular calcium
4. Ca causes exocytosis of vesicles filled with epi

Question 6

Name 2 effects of norepi in the brain

Answer 6

increased arousal

increased aggression

Question 7

Describe the effects of epi

(2 CV, 3 metabolic)

Answer 7

• CV: Increase HR, inotropy (beta-1)
• Metabolism: Increase lipolysis and glycogenolysis (beta-2), decrease insulin

Question 8

Compare the activity of epi and norepi on GPCR’s

Answer 8

• Epi activates beta adrenergic receptors more
• Norepi activates alpha adrenergic receptors more