Adrenal Catecholamines Flashcards
What is the connection between the brain and the adrenal medulla?
There is a direct connection between the hypothalamus and the adrenal medulla
Which cells store catecholamines?
Medulla chromaffin cells or pheochromocytes contain secretory vesicles with epi or norepi
What are the interconnected neurons of the sympathetic NS?
Brain –> preganglionic neurons –> postganglionic neurons(secrete NE as NT) or innervate adrenal medulla (secrete E into the bloodstream (circulate to tissues targeting alpha or beta adrenergic receptors)
What is E/NE secretion stimulated by?
Acetylcholine, uses nicotinic AchR
How are catecholamines synthesized?
- Tyrosine hydroxylase adds a hydroxyl group to make DOPA
- DOPA to dopamine, by DOPA decarboxylase, which removes carboxyl
- Dopamine enters storage vesicles
- hydroxyl added by dopamine-beta0hydroxylase to make norepi –> diffuses into cytoplasm - To make epi, methyl is added by phenylethanolamine n-methyltransferase –> epinephrine
Where is most of the epi made?
In chromaffin cells
What is the rate limiting step of catecholamine synthesis?
Tyrosine hydroxylase adding a hydroxyl group to make DOPA
What controls PMNT production?
gene is induced by cortisol, levels of cortisol stimulate production of epi
What is alpha 1-adrenergic receptor signaling?
Agonist binds to the galpha 1 GPCR –> activation of phospholipase C –> IP3 and DAG –> DAG activates PKC, IP3 increases Ca stores in the cell –> Ca dependent protein kinase activation
What is Beta-adrenergic signaling?
Agonist binds to beta receptor (alpha s) –> Activation of AC –> cAMP –> activation of R2C2 protein kinase –> 2C –> activates enzyme
What is alpha 2-adrenergic signaling?
Agonist binds to alpha 2 receptor (g alpha i) –> inhibition of AC
What are the effects of epinephrine and norepinephrine?
Increased alertness due to inc blood flow and glucose metabolism. Increased rate and force of heart contraction (B-AR). Increased peripheral vasoconstriction (a1 and a2-AR). Decreased blood flow to non-essential tissues. Increased O supply by bronchial dilation B-AR. Increased glucose production by glyconeogenesis and glycogenolysis. increased lipolysis (B-AR, inhib by a2-AR), increased glyconeogenesis
What receptor do adrenal catecholamines act on to induce increased heart rate and force of contraction?
Beta adrenergic receptors
What receptor do adrenal catecholamines act on to induce vasoconstriction?
alpha 1 and alpha 2 adrenergic receptors
What receptor do adrenal catecholamines act on to induce bronchial dilation?
beta adrenergic.
