Adrenal Medulla Flashcards
dopamine enters _______ and is converted to norepinephrine by _______
the granules
dopamine B-hydroxylase
Catecholamine effect on pupils?
dilation
Catecholamine effect on alertness?
increased
What is the rate limiting step of catecholamine synthesis
tyrosine hydroxylase converting tyrosine to DOPA
Catecholamine effect on GI activity?
decreased
synthesis of catecholamines occurs in the ____ cells
chormaffin
What are the two main enzymes of catecholamine degradation?
- monoamine oxidase (MAO)
2. Catechol-O-methyltransferase (COMT)
What is the only cause of HYPERfunction of adrenomedullary catecholamine synthesis
pheochromocytoma
monoamine oxidase (MAO) converts norepinephrine into __________ and is then excreted in the urine as __________
MHPG - 3-methoxy-4-hydroxyphenylglycol
VMA - 3-methoxy-4-hydroxymandelic acid
Pheochromocytoma produces catecholamines ___x more than normal
20
tyrosine hydroxylase converts ______ to _______
which part of the cell?
tyrosine to DOPA
cytosol
Which enzyme predominantly degrades epinephrine?
Catechol-O-methyltransferase (COMT)
Chronic stress activates which enzyme in the pathway of catecholamine synthesis
HOW
tyrosine hydroxylase
increased expression and concentration
(acute stress = activity of TH)
Catechol-O-methyltransferase (COMT) degrades which catecholamine?
epinephrine
Catecholamine effect on bronchioles?
dilation
phenylethanolamine-N-methyltransferase “PNMT” is regulated by:
cortisol
storage of catecholamines:
\_\_\_% = norepinephrine \_\_\_% = epinephrine
15% epinephrine
85% norepinephrine
half life of catecholamine
~2 min
What converts DOPA to dopamine?
amino acid decarboxylase
monoamine oxidase (MAO) degrades which catecholamine?
norepinephrine
Which enzyme predominantly degrades norepinephrine?
monoamine oxidase (MAO)
clinical manifestations of pheochromocytoma
What age is it usually found/diagnosed?
- hypertension
- rapid pulse
- chest pain
- sweating
- headache
- hyperglycemia***
- fatigue
40’s/50’s
What can be measured in the urine that serves as an index of SNS activity or pathology
VMA - 3-methoxy-4-hydroxymandelic acid
MOST of the norepinephrine made in the granules is ______________
SOME of the norepinephrine made in the granules is ______________
MOST = converted to epinephrine in the cytosol
SOME = stored in granules
phenylethanolamine-N-methyltransferase “PNMT” converts _________ to ________
which part of the cell?
norepinephrine to epinephrine
cytosol
Where do you find Catechol-O-methyltransferase (COMT)
heart, liver, kidney
Acute stress activates which enzyme in the pathway of catecholamine synthesis
HOW
tyrosine hydroxylase
ACTIVITY
(chronic stress = increased expression and concentration of TH)
What enzyme converts tyrosine to DOPA
tyrosine hydroxylase
Catechol-O-methyltransferase (COMT) converts epinephrine into __________ and is then excreted in the urine as __________
MHPG - 3-methoxy-4-hydroxyphenylglycol
VMA - 3-methoxy-4-hydroxymandelic acid
catecholamine effects on the cardiovascular system
- increased cardiac contractility
- increased heart rate
- increased conduction
- increased blood pressure
- increased arteriolar vasoconstriction in the renal, splanchnic and cutaneous bed
amino acid decarboxylase converts _____ to _____
which part of the cell?
DOPA to dopamine
cytosol of the cell
What is the only cause of HYPOfunction of adrenomedullary catecholamine synthesis
post-adrenalectomy surgery
dopamine B-hydroxylase converts _____ to _____
which part of the cell?
dopamine to norepinephrine
granules
epinephrine mobilizes fuels of stress by:
- increased glycogenolysis
- inhibition of glycogen synthesis
- increased gluconeogenesis
- inhibition of insulin secretion
- increased glucagon secretion
- increased lipolysis
What is pheochromocytoma?
How can it be detected?
catecholamine-secreting tumor
VMA (3-methoxy-4-hydroxymandelic acid) in the urine
what enzyme converts norepinephrine to epinephrine
phenylethanolamine-N-methyltransferase
“PNMT”
Secretion of catecholamines occurs during which events (5)
- fight-or-flight
- hypotension
- shock
- heart failure
- hypoglycemia
What is the precursor molecule for all catecholamines
tyrosine
catecholamine effects:
fast/slow ?
short-acting/ long lasting?
fast
short-lived
Why does epinephrine mobilize fuels in times of stress?
to sustain glucose production for use by the CNS
cortisol regulates which enzyme in catecholamine synthesis?
phenylethanolamine-N-methyltransferase
“PNMT”
Where do you find monoamine oxidase (MAO)
neuronal cytoplasm
