Neurochemistry Terms

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categories of neurochemicals
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-neurotransmitter (released by neurons) -neuromodulator (released by neurons) -neuropeptide (released by neurons) -neurohormone (released by neurons) -hormone
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Ionotropic
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transmitter-gated ion channels
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metabotropic
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G-protein coupled receptors -2nd messenger system
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termination of nt effect
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-reuptake -enzymatic deactivation -diffusion (rarely)
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ACh
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-acetylcholine -primary NT secreted by output CNS cells -pons: arousal -hippocampus: learning and memory -basal ganglia: learning and memory
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where are ACh neurons found
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-autonomic ganglia (like the heart) -neuromuscular junction (activation muscle movement)
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ACh side effects
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-memory dysfunction -dry mouth -constipation -blurred vision -urinary retention ..etc
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nicotinic receptor
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-always excitatory -very rapid -5 subunits around transmembrane channel which conducts primarily Na+ -receptors desenstitive when subjected to continuous agonist; after short time it resensitize -ACh acts as NT
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muscarinic
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-G protein coupled, muscarine is agonist -excitatory and inhibitory -slower onset, longer lasting action -2nd messenger (cAMP, Pl, cGMP) -ACh acts as neuromodulator
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what can block ACh?
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botulinum toxin (botox) -a natural toxin that blocks ACh release -paralyzes area where injected -helps w/ sweating and migraine headaches
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What promotes release of ACh?
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-black widow spider -can victims to eat them -toxin produces a massive release of ACh -basically massive release of ACh causes all muscles to contract and this in turn causes no release
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Alzheimer’s disease
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-loss of ACh -death of neurons in nucleus basalis of mynert
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Most drugs block acetylcholinesterase, what is the result of that?
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increase of ACh in the synapse
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monoamines
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-catecholamines ( DA, NE, EPI) -indolamines include (5-HT)
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dopamine
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-used by several systems
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nigrostriatal
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substance nigra to basal ganglia -motor control (Parkinson’s)
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mesolimbic
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ventral tegmental area to the limbic system -reward (drug seeking)
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mesocortical
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ventral tegmental area to frontal cortex -short term memories, planning, and problem solving
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Parkinson’s disease
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-degeneration of nigrostiatal system -L dopa as therapeutic drug
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what are some drugs that block dopamine?
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chlorpromazine
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what blocks the reuptake of dopamine?
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cocaine, amphetamines, and methylphenidate
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Norepinephrine
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-synthesized from DA within vesicles – locus coeruleus gives rise to NE fiber system throughout brain -in the sympathetic ns -promotes peripheral changes consisten w/ fight or flight
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MAO: Dietary Restrictions
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-due to hypertensive crisis -patients must avoid substances containing tyramine, dopamine, or sympathomimetics and many other drugs
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what is serotonin’s precursor?
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tryptophan -tryptophan found in high levels in turkey and also found in milk
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MAO
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degrades monoamines (NE, EPI, SE, DA) -used in depression -can be dangerous
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where are serotonin cell bodies located?
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in brainstem raphe nuclei and project to cortex
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What does serotonin regulate?
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mood, food intake, sleep, arousal, and pain
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SSRIs
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-help w/ depression, anxiety disorders, personality disorders, premature ejaculation -shows little binding affinity for noradrenaline and dopamine transporters
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MDMA
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causes the transporters to run in reverse; may cause permanent effects
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Histamine
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-basis of many allergic and inflammatory reactions when released from mast cells -also in brain
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histamine receptors
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all receptors are g-protein coupled
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behavioral effects of histamine
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-arousal & cognitive function -psychomotor coordination -feeding/satisfaction -sexual behavior -hormone release -nociception
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antihistaminic side efffects
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-sedaton -drowsiness -hypotension -weight gain
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glutamate
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-main excitatory NT
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PCP and Ketamine
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are noncompetitive antagonists for a subset of glu receptors (NMDA)
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Hypoxia
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causes high level of glu release, which leads to excitotoxicity
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GABA
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-synthesized from glutamic acid -main inhibitory NT -inhibition -control brain stability (prevents seizures) -acts via 2 receptor types (A & B)
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GABAa receptors
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-have 5 binding sites and sites for: barbiturates (“downers”/ alcohol) benzodiazepines (valium) other anticonvulsants
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Catecholamine Synthesis- rate limiting step
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tyrosine hydroxylase (can get from diet) – the amount of L dopa can be made from tyrosine but depends on tyrosine hydroxylase

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