Essay About Gi Tractexcitatory And Action Potential

Membrane Potentials
Membrane PotentialsResting Membrane Potential (rmp)[pic 1]Action Potential[pic 2]Synaptic Transmission of Action Potentials[pic 3]Basic mechanism[pic 4]NeurotoxinsThe –caines:  Tetrodotoxin:  Scorpion Toxins:  Latrotoxin:  Botulinum toxin:  Nicotine:  α-bungarotoxin:  Physostigmine:  Some Important Neurotransmitters/Receptors and Their LigandsReceptorReceptorDistributionGeneral FunctionNotesReceptorAgonist/AntagonistAcetylcholine (ACh)Nicotinic receptors————Muscarinic receptorsThroughout body, esp. neuromuscular junction and brain————PNS receptors:  lungs, CV system, GI tractExcitatory————Excitatory (GI) orInhibitory (CV)Activates contraction of skeletal muscles;————Target of some anti-asthmatic, anti-diarrheal drugsAg – nicotine (low conc.)Antag – nicotine (high conc.)————Ag – muscarineAntag – atropineDopamineMainly CNSExcitatoryorinhibitoryDopamine plays a key role in Parkinsonism and in development of addictionsAg – ProvigilAntag – Hadol (anti-psychotic)γ-amino Butyric Acid (GABA)CNSTHE inhibitory neurotransmitter in the CNS, especially in the brainGABA receptors mediate effects of ethanol and many hypnotics (barbiturates, Valium, Librium, Versed, etc.)Ag – Valium, etc.Antag – picrotoxinGlycineCNSInhibitory, especially important in spinal cordRelease blocked by tetanus toxin (destroys SNARE)Ag – taurineAntag – strychnineGlutamate & aspartateThroughout CNSTHE excitatory neurotransmitters in the CNSInvolved in excitotoxicity following a strokeAg – domoic acidAntag – PCPSerotoninThroughout CNS, esp. in medulla, higher brain centers; spinal cordExcitatoryorInhibitoryDrugs targeting serotonin synapses (SSRIs) are used to treat depression,  bulimia, etc. Ag – LSD, mescaline, psylocibinAntag – palonostron (anti-nausea in chemo.)Catecholamines (epinephrine, norepinephrine, dopamine)Brain; sympathetic nervous system & adrenal glandsExcitatoryorInhibitoryEssential in brain’s regulation of CV, GI, and respiratory systemsAg – Albuterol (asthma)Antag – β-blockers (e.g., Inderol)Peptides(e.g., endorphins, Substance P)Throughout body, esp. in CNS and GI tractExcitatoryorInhibitoryRegulate sleep-awake cycles in brain, release of hormones, endogenous analgesicsChronic pain (Substance P) Ag – opioids (in the case of endorphin receptors)Antag – synthetic anti-hypertensives(?)Nitric oxide (NO)Throughout bodyInhibitoryInhibits vasoconstriction → enhanced blood flowNitroglycerine (alleviates angina pain) is bioactivated → unstable intermediate → NONone knownCarbon monoxide (CO)Retina; brain, esp. hippocampus; GI tractExcitatoryorInhibitoryRequired for long-term memory formation?  NO often doesn’t work without CO.None knownCannabinoid (really Anandemide)Throughout brain, bodyMacrophagesExcitatoryorInhibitoryAgonists → analgesia, ↑ appetite, ↓leukocyte recruitment in inflammationAg – THC, many syntheticsAntag – rimonabant (anti-obesity drug)Adenosine(a neuromodulator, meaning it alters responses to ‘real’ neurotransmitters)Throughout CNS, esp. in brainUsually InhibitoryContributes to alcohol’s effects on coordination and development of alcohol tolerance, also important in opioid analgesia.Ag – many syntheticAntag –caffeine, theophyllineVanilloidEndings of peripheral nerves – especially pain receptorsExcitatoryAg – capsaicinAntag – capsazepine (synthetic topical analgesic)