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Neurotransmitters are chemicals that transmit signals between neurons. They are synthesized in the presynaptic neuron, stored in vesicles, and released into the synaptic cleft upon arrival of an action potential. They then bind to receptors on the postsynaptic neuron, eliciting a biological response. Some major neurotransmitters include acetylcholine, dopamine, serotonin, GABA, and glutamate. Otto Loewi first discovered acetylcholine as a neurotransmitter in 1921. Neurotransmitters are classified as either excitatory or inhibitory depending on their effect on the postsynaptic neuron. Buffers help maintain pH and consist of a weak acid/base and its conjugate that can absorb hydrogen or hydroxide ions.
![NeurotransmitterNeurotransmitters are endogenouschemicals which relay, amplify, and modulate signals between a neuron and another cell.[1] Neurotransmitters are packaged into synaptic vesicles that cluster beneath the membrane on the presynaptic side of a synapse, and are released into the synaptic cleft, where they bind to receptors in the membrane on the postsynaptic side of the synapse. Release of neurotransmitters usually follows arrival of an action potential at the synapse, but may follow graded electrical potentials. Low level "baseline" release also occurs without electrical stimulation.](https://image.slidesharecdn.com/presentationbiochemistry-100807034354-phpapp02/85/Presentation-3-320.jpg)
![DiscoveryIn the early 20th century, scientists assumed that synaptic communication was electrical. However, through the careful histological examinations of Ramón y Cajal (1852-1934), a 20 to 40 nm gap between neurons, known today as the synaptic cleft, was discovered and cast doubt on the possibility of electrical transmission. In 1921, German pharmacologist Otto Loewi (1873-1961) confirmed the notion that neurons communicate by releasing chemicals. Furthermore, Otto Loewi is accredited with discovering acetylcholine—the first known neurotransmitter. [2]](https://image.slidesharecdn.com/presentationbiochemistry-100807034354-phpapp02/85/Presentation-4-320.jpg)
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- 1. NeurotransmittersProperties of neurotransmitters:synthesized in the presynapticneuron2) Localized to vesicles in the presynaptic neuron3) Released from the presynaptic neuron under physiological conditions4) Rabidly removed from the synaptic cleft by uptake or degradation5) Presence of receptor on the post-synaptic neuron.6) Binding to the receptor elicits a biological response
- 3. NeurotransmitterNeurotransmitters are endogenouschemicals which relay, amplify, and modulate signals between a neuron and another cell.[1] Neurotransmitters are packaged into synaptic vesicles that cluster beneath the membrane on the presynaptic side of a synapse, and are released into the synaptic cleft, where they bind to receptors in the membrane on the postsynaptic side of the synapse. Release of neurotransmitters usually follows arrival of an action potential at the synapse, but may follow graded electrical potentials. Low level "baseline" release also occurs without electrical stimulation.
- 4. DiscoveryIn the early 20th century, scientists assumed that synaptic communication was electrical. However, through the careful histological examinations of Ramón y Cajal (1852-1934), a 20 to 40 nm gap between neurons, known today as the synaptic cleft, was discovered and cast doubt on the possibility of electrical transmission. In 1921, German pharmacologist Otto Loewi (1873-1961) confirmed the notion that neurons communicate by releasing chemicals. Furthermore, Otto Loewi is accredited with discovering acetylcholine—the first known neurotransmitter. [2]
- 5. Neurotransmitters found in the nervous systemEXCITATORYAcetylcholineAspartate Dopamine HistamineNorepinephrine Epinephrine Glutamate SerotoninINHIBITORYGABA Glycine
- 6. What kinds of neurotransmitters are there?AMINO ACID transmittersGlutamateGABA (γ-aminobutyric acid)
- 7. NeurotransmitterDerived fromEnzymeHistamineHistidineHistidine decarboxylaseGABA(γ-Amino butyrate)GlutamateGlutamate decarboxylaseNitric OxideArginineNitric Oxide Synthase Other Neurotransmitters:
- 8. Neurotransmitter MoleculeDerived FromSite of SynthesisAcetylcholineCholineCNS, parasympathetic nervesSerotonin5-Hydroxytryptamine (5-HT)TryptophanCNS, chromaffin cells of the gut, enteric cellsGABAGlutamateCNSHistamineHistidinehypothalamusEpinephrinesynthesis pathwayTyrosineadrenal medulla, some CNS cellsNorpinephrinesynthesis pathwayTyrosineCNS, sympathetic nervesDopaminesynthesis pathwayTyrosineCNSNitric oxide, NOArginineCNS, gastrointestinal tract
- 9. BuffersBuffer Solutions resist a change in pH
- 10. Buffers contain relatively large concentrations of either
- 11. An acid, HA and its conjugate base A-
- 12. A base, B, and its conjugate acid (BH+) Buffers
- 13. BuffersNH3 to react with H+
- 14. When H+ is added, it reacts essentially to completion with the weak base presentH+ + A- HA orH+ + B BH+
- 15. When OH- is added, it reacts essentially to completion with the weak acid presentOH- + HA H2O + A-OH- + BH+ H2O + B
- 16. pH = pKa + log (base/acid)
- 17. Want pH pKa 1
- 18. pH determined by Ka of acid and ratio of acid/conjugate baseor Kb of base and ratio base/conjugate acid
- 19. Buffer Table
- 20. Buffer ChoiceChoose a pKa near the desired pH
- 21. pH = pKa + log (base/acid)
- 22. 4.0 = 3.74 + log (base/acid)
- 23. 0.26 = log (base/acid)
- 24. 10.26 = 1.8 = (Na formate / formic acid)
- 25. Ammonia pKb = 4.74 pKa = 14.00 – 4.74 = 9.26NH3 / NH4Cl used to buffer around pH 9.26
- 26. Biological Uses In biological systems (saliva, stomach, and blood) it is essential that the pH stays ‘constant’ in order for any processes to work properly. e.g. If the pH of blood varies by 0.5 it can lead to unconsciousness and coma Most enzymes work best at particular pH values.Other Uses Many household and cosmetic products need to control their pH values.Shampoo Buffer solutions counteract the alkalinity of the soap and prevent irritationBaby lotion Buffer solutions maintain a pH of about 6 to prevent bacteria multiplyingOthers Washing powder, eye drops, fizzy lemonade