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40 Cards in this Set

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What is the main, most potent function of epinephrine?
Muscle gluconeogenesis.
How does epinephrine affect glycolysis?
Epinephrine suppresses glycolysis everywhere except the heart.
What is the most potent drug for increasing liver gluconeogenesis?
Cortisol.
What is the most potent drug for increasing liver glycogenolysis?
Glucagon.
How does epinephrine affect lipid metabolism?
Activates lipolysis to release FFA's and glycerol into circulation via HSTL.
What two types of cells are found in the adrenal medulla?
1) Epinephrine releasing chromaffin cells (80%).
2) Norepinephrine releasing chromaffin cells (20%).
Detail the catecholamine biosynthesis pathway.
Tyrosine --(TH)--> Dopa --> Dopamine --(DBH)--> NE --(PNMT w/SAM)--> Epinephrine
What is Tyrosine Hydroxylase (TH)?
The enzyme which facilitates the rate limiting step of catecholamine biosynthesis: Tyrosine --> Dopa.
What is Dopamine-β-Hydroxylase (DBH)? What cofactors does it require?
Membrane bound enzyme that converts Dopamine --> NE.
Requires Vit C and Cu.
What is Phenylethanolamine-N-methytransferase (PNMT)? What cofactor does it require?
PNMT converts NE --> EPI.
Requires "SAM" as a cofactor.
Describe neuronal control of epinephrine release.
Cholinergic nerves release ACh, which binds to nicotinic cholinergic receptors on chromaffin cells, inducing TH and DBG to be released.
Describe hormonal control of epinephrine release.
Cortisol from the adrenal cortex travels down to the adrenal medulla and induces PNMT, and some DBG release to sustain epinephrine secretion.
What are the 2 ways catecholamines are inactivated?
1) Taken back up into the cell and re-stored in the sympathetic nerves.
2) Inhibited, metabolized, and excreted.
What is MonoAmine Oxidase (MAO)?
A mitochondrial enzyme that oxidizes (and inactivates) catecholamines.
What is Aldheyde Dehydrogenase (AldDH)?
An enzyme that converts aldehydes to acids, that must accompany MAO.
What is Catchol-O-Methyl Transferase (COMT)?
Converts catecholamines to inactive phenols, like metanephrine and normetanephrine. Used in conjunction with "SAM".
What are Vanillylmandelic Acid (VMA) and metanephrines?
Excreted metabolites of inactivated catecholamines. Measured to determine pathology.
*Describe the two enzymatic pathways of catecholamine catabolism.
EPI/NE --(COMT)--> Metanephrine/Normetanephrine --(MAO)--> VMA
EPI/NE --(MAO)--> Dihydroxymandelic acid --(COMT)--> VMA
How are catecholamines used in synapses to skeletal muscle?
Postganglionic fibers secrete ACh onto nicotinic cholinergic receptors on skeletal muscle.
How are catecholamines used in synapses in the parasympathetic nervous system?
Preganglionic synapse secretes ACh onto a nicotinic cholinergic receptor (close to the effector target) and the postganglionic synapse secretes ACh to a muscarinic cholinergic receptor on the target organ.
How are catecholamines used in synapses of the sympathetic nervous system?
Preganglionic fiber secretes ACh onto the nicotinic cholinergic receptor, and the postganglionic fiber secretes NE onto α-, β-adrenergic receptors.
How are catecholamines used in the adrenal medulla?
Neurons synapse onto the chromaffin cells of the adrenal medulla and release ACh, which binds to nicotinic cholinergic receptors on chromaffin cells and produce EPI (and some NE).
Which catecholamine reaches "hormonal threshold" just by standing?
Epinephrine.
Which catecholamine reaches "hormonal threshold" only during heavy exercise?
Norepinephrine.
How are NE and T4 involved with thermogenesis?
When cold is sensed by the hypothalamus, EPI binds to adrenergic receptors on brown adipose tissue, send signals to the the nucleus to produce UCP-1. UCP-1 will go to the mitochondria to make heat by uncoupling the ETC. T4 will enter the cell, convert to T3, which enters the nucleus, and do the same thing.
What is pheochromocytoma?
Chromaffin cell tumor that hypersecretes EPI and some NE. Both EPI and NE are well above threshold with this tumor.
What are symptoms of pheochromocytoma?
Hypertension, tremor, sweating, anxiety.
What tests are done to detect pheochromocytoma?
Measure urinary VMA/metanephrines, adrenal scans, and sometimes plasma NE/EPI are measured as well.
What is Multiple Endocrine Neoplasm (MEN)?
An inherited tumor in the parathyroid, pancreas, pituitary, and other locations. Occasionally is seen as part of pheochromocytomas.
What is primary autonomic dysfunction?
A severe deficiency of the adrenal medulla causing standing hypotension, impaired sweating, and bladder problems due to low EPI/NE levels.
Why is pheochromocytoma called the "10% tumor"?
10% of all cases are malignant, bilateral, pediatric, familial, recurring, associated with MEN, present with stroke, outside adrenal gland.
Where is melatonin synthesized?
In the pineal gland.
What is the pattern of melatonin secretion?
Circadian rhythm, high levels at night, low levels in light.
What is N-acetyltransferase?
A regulatory enzyme that is activated by nighttime release of NE, and catalyzes melatonin synthesis. It converts serotonin to N-acetyl serotonin.
Describe the pathway of melatonin biosynthesis.
Tryptophan --(TH)--> Serotonin --(N-Acetyltransferase)--> N-Acetyl Serotonin --(SAM)--> Melatonin.
What physiological role does melatonin play?
Unclear, but possible sleep regulation, regulation of reproduction, anti-oxidant.
In the response to stress, what hormones are activated?
CRH from the hypothalamus, which stimulates ACTH and Cortisol release from adrenal cortex.
In the response to stress, what catecholamines are activated?
Norepinephrine and epinephrine from the adrenal medulla.
What is the result of norepinephrine sympathetic release?
Sympathetic arousal, aggression, and behavioral activation.
What is the result of cortisol and epinephrine sympathetic release?
Mobilize glucose from the liver and muscle into the blood circulation, and to increase glycolysis in the heart only.