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62 Cards in this Set
- Front
- Back
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Acronym for Serotonin drugs:
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Little Boys scare fat people sitting calmly on airplanes
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What are 3 direct agonists of serotonin receptors?
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Little boys scare
-Lysergic acid diethylamide -Buspirone -Sumatriptan |
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What are 3 indirect agonists of serotonin receptors?
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-Fluoxetine
-Phenelzine -Sibutramine (fat people sitting) |
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What are the 3 antagonists of serotonin receptors?
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-Cyproheptadine
-Ondansetron -Alosetron (calmly on airplanes) |
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Where is serotonin found?
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Widely in nature - plants, venoms, humans.
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What is Serotonin also called?
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5-hydroxytryptamine - 5HT
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What is serotonin synthesized from?
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Trytophan
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What is the rate limiting step in Serotonin synthesis?
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Tryptophan hydroxylase catalyzed conversion of Tryptophan into 5-hydroxytryptophan
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Why isn't Tryptophan hydroxylase the RLS in the CNS?
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Because there are low concentrations of Tryptophan in the brain and that is what limits the synthesis.
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What can significantly impact the amount of Serotonin in the brain?
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Dietary supplies - ie eating turkey at thanksgiving
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What is the 2nd step in Serotonin synthesis?
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Conversion of 5-hydroxy tryptophan into Serotonin by L-AAA decarboxylase
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Where is Serotonin synthesized?
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In almost all tissues except Platelets
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What can further happen to 5-hydroxytryptamine (Serotonin)?
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Conversion into Melatonin
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What enzyme converts Serotonin (5-HT) into Melatonin?
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5-HT N-acetylase
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Where does Melatonin synthesis occur?
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In the pineal gland
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What 2 enzymes metabolize Serotonin?
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-Monoamine oxidase
-Aldehyde dehydrogenase |
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What is the product of metabolism of Serotonin?
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5-hydroxyindole acetic acid
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How is neuronal action of Serotonin terminated?
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By a high affinity reuptake system and intraneuronal MAO
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What are the 3 main sites where Serotonin is found in the body?
What % is at each site? |
-Enterochromaffin cells of GI mucosa - 90%
-Blood platelets - 8% -CNS - 2% |
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At which sites does synthesis and storage take place?
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-ENS
-CNS |
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What is the release and turnover of Serotonin in the gut like?
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Slow - takes about 1 day
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What does Serotonin in the gut function in?
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The enteric nervous system
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Where is Serotonin stored in platelets?
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In vesicles with ATP
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How do platelets acquire Serotonin?
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-NOT by synthesis
-Remove it from plasma |
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Where in the CNS is serotonin located?
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In cell bodies in the midbrain raphe nuclei
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Where in the brain do the cell bodies project?
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Both caudally and rostrally
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What is the turnover of Serotonin in the CNS like?
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Rapid - takes less than 4 hrs
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What are the serotonergic neurons in the CNS affected by?
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Many psychoactive drugs
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What is the nature of most of the serotonin receptors?
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GPCR
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Which serotonin receptor is not GPCR? What is it?
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5HT-3 - a ligand-gated cation channel
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How many 5HT1 receptor subtypes are there?
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5; A-E
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What Gprotein are the 5HT1 subtype receptors couple to?
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Gi - inhibits Adenylate cyclase
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What does 5HT1a do in addition to inhibiting adenylate cyclase?
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-Opens a K channel
-Closes Calcium channel |
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What Gprotein are the 5HT2 subtype receptors couple to?
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Gq
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What does Gq do?
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Activates PLC to cleave PIP2 to IP3 and DAG, activating PKC and increasing calcium
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What is 5-HT3?
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A ligand gated ion channel
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What do the receptor subtypes 5HT4-5-6-and 7 do?
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Activate adenylate cyclase or unknown
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By what Gprotein do the receptors 5HT4,6, and 7 activate adenylate cyclase?
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Gs
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What 3 effects does Serotonin have on the enteric nervous system?
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Contraction of GI smooth muscle
-Increased tone -Peristalsis -Diarrhea |
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What is Carcinoid syndrome?
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A tumor of enterochromaffin cells where Serotonin and Bradykinin are secreted.
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What 2 symptoms will result from Carcinoid syndrome?
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-Severe diarrhea
-Asthma |
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How can Serotonin cause Emesis?
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By hitting 5HT3 receptors in the brain and GI tract
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What are 2 effects Serotonin has on the cardiovascular system?
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Both Vasoconstriction and Vasodilation
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Where does Serotonin cause Vasoconstriction?
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-Large arteries and Veins in most vascular beds
(Lungs, kidnes, cranial) |
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What 2 receptor subtypes mediate the vasoconstriction directly, and where are they located?
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5HT2 - on smooth m cells
5HT1D - in the brain |
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What 2 mechanisms mediate vasoconstriction by Serotonin INDIRECTLY?
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-Amplification of alpha adrenergics
-Displacement of Norepi from adrenergic nerves |
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Where does Serotonin stimulate Vasodilation?
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-Coronary arteries
-Arterioles -Skeletal muscle -Cutaneous blood vessels |
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How does Serotonin stimulate the Bezold-Jarisch reflex?
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By stimulating chemoreceptors in coronary vessels
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What is the result of Serotonin stimulating coronary chemoreceptors?
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Activation of vagal nerves
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What is the vagal response to serotonin? (3 effects)
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-Hypotension
-Bradycardia -Hyperventilation |
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What does Serotonin do for Platelets?
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Causes aggregation
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So where is Serotonin found in the brain?
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In cell bodies in the Midbrain raphe nuclei
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How is Serotonin involved in so many things in the CNS?
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It projects both rostrally and caudally
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How can we tell that Serotonin is involved in sensory perception?
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By the effects of LSD
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What type of sleep is Serotonin involved in?
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Slow wave deep sleep
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What 2 things is Serotonin involved in regulating?
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-Temperature
-Neuroendocrine release of tropic hormones |
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What type of memory is Serotonin particularly involved in?
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Short-term
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How is serotonin in the CNS involved in emesis?
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Via 5HT3 receptors in BOTH the brain and GI tract
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What mental things is Serotonin involved with?
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-Pain perception
-Drug abuse -Anxiety -Mental illness |
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What are 2 ways that Serotonin is involved in Drug abuse?
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-It reinforces the drug
-Learning/Rewards |
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What serotonin receptor mediates Anxiety?
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5HT1a
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What 5 mental illneses is Serotonin involved in?
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-Affective (depression)
-Schizophrenia -OCD -Aggressive behavior -Anxiety disorders |
