Adrenal Medulla

What percentage of chromatin cells secret epinephrine and what percent secrete norepinephrine

80;20

What percentage of epinephrine comes from teh adrenal glands

ALL

What percentage of circulating norepinephrine comes from adrenal glands

30%

What is responsible for 70% of norepinephrine secretion

Postganglionic sympathetic neurons

How does the cortex regulate the medulla

GCs: inhibit neuronal differentiation and stimulate PNMT expression

Synthesis of catecholamines aka epinephrine

Tyrosine → DOPA → Dopamine → norepinephrine → epinephrine

What is the major regulator of catecholamines

Sympathetic nervous system via preganglionic neurons

Series of events leading to catecholamines release

Nicotinic ACh receptors bind ligands

cell depolarizes

Voltage gated ion channels open

Increased cytoplasmic calcium

Exocytosis of catecholamines

Describe metabolism of catecholamines

Unbound; Inactivated in cells by MAO or COMT and diffuse out and excreted via urine

Do catecholamines have a long or short half life

Very short

What receptors do epi and norepinephrine bind

Adrenergic receptors

What type of adrenergic receptors have a higher affinity for epi

Beta 2

What type of GPCRs are the different adrenergic receptors

B=Gs

A1=Gq

A2=Gi

What is the result of Gs receptor activation and overall result

Relaxtion; Increased cAMP production → inhibits MLCK activity → decreased phosphorylation and ATPase activity

Describe activation of a Gi linked receptor and overall result

Contraction; Decreased cAMP → decreased MLCK inhibition → increased phosphorylation and ATPase activity

Describe the activation of Gq repertors and overall result

Contraction; Phospholipase C activation → DAG+IP3 → Ca2+ influx → Ca2+ binds calmodulin and activates MLCK → increase phosphorylation and ATPase activity

What is the “goal” of catecholamine activation

Increase availability of nutrients and O2 as well as delegation of energy during stressful events.