What is the embryological origin of the adrenal medulla?
Modified part of SNS
What happens in the adrenal medulla?
Modified postganglionic sympathetic neurons (chromaffin cells) secrete neurohormones (catecholamines).
What are the 3 catecholamines?
- Adrenaline (only made in adrenal medulla)
- Noradrenaline
- Dopamine
What are secretions from the adrenal medulla stimulated by?
Preganglionic sympathetic neurons.
What is the precursor to dopamine?
DOPA
What converts tyrosine to DOPA?
Tyrosine hydroxylase
What converts DOPA to dopamine?
Amino acid decarboxylase
What converts dopamine to noradrenaline?
Dopamine-beta-hydroxylase
What converts noradrenaline into adrenaline?
PNMT
Where is PNMT found outside of the CNS?
In the adrenal medulla
What are the adrenomedullary hormone actions on flight-or-fight responses?
↑cardiac rate and contractility, ↑TPR, ↑BP
What are the adrenomedullary hormone actions on metabolic effects?
↑glucose & FFA, ↑BMR
What are the adrenomedullary hormone actions on central effects?
↑arousal & alertness
What are the adrenomedullary hormone actions on stress responses?
- Physical
- Psychological
Have there been any recognised hyposecretion disorders of the adrenal medulla?
No
What is adrenomedullary hypersecretion disorder?
- Pheochromocytomas (tumor)
- Rare
- Potentially deadly (hypertension)
- Treatment: removal
What role does stress play in cortisol secretion?
- Nonspecific stimuli (“stressors”) disrupt homeostasis
- Two types of stress elicit two responses
- Acute stress results in the fight‐or‐flight reaction
- Chronic stress elevates cortisol levels, which suppresses immune responses
- Acute stress results in the fight‐or‐flight reaction
- Chronic stress elevates cortisol levels, which suppresses immune responses
What is the MoA of stress on the hypothalamus?
See image.
