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UT Arlington PSYC 3322 - The Workings of Neurons and Neurotransmitters

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PSYC 3322 1st Edition Lecture 5Outline of Last Lecture II. Electricity and Electrical StimulationIII. Tools for Measuring a Neuron’s Electrical ActivityIV. Electrical Activity of a MembraneV. How Neurons Integrate InformationOutline of Current Lecture VI. How Do Neurons Communicate?VII. A Chemical MessageCurrent LectureHow Do Neurons Communicate?Charles Scott Sherrington- Forty years after Cajal/Golgi’s debate about how neurons work. Sherrington was interested in reflexes, and he conducted an experiment on a dog hanging from a harness to test the dog’s reflexes. Sherrington pinched the dog’s paw and saw how many times it took for the dog to raise its paw reflexively. Sherrington wenton to coin the word “synapse.” Presumably, the delay in reactions occur at the synapse.The speed of conduction along an axon is about 40 m/s. The speed of a conduction through a reflex arc is slower and more variable, about 15 m/s or less.Review: Resting Membrane Potential- Recording Membrane Potential: different in electrical charge between in and out of the cell.- Inside of the neuron is negative with respective to the outside.- Resting Membrane Potential is about -70 mV.- Membrane is polarized (carries a charge).Ionic Basis of Resting Potential- Even Distribution- factors contributing to even distribution:o Random motion—particles tend to move down their concentration gradient.These notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.o Electrostatic pressure—like repels like, opposites attract.- Uneven Distribution- factors contributing to uneven distribution:o Selective permeability to certain ions.o Sodium-potassium pumps.Ions Contributing to Resting Potential- Sodium (Na+)- Chloride (Cl-)- Potassium (K+)- Negatively charged proteins (A-). Synthesized in neuron, found primarily within neuron.The Neuron at Rest- Negative ions move through ion-specific channels.- K+ and Cl- pass readily.- Little movement of Na+.- A- ions don’t move; they’re trapped.- Equilibrium Potential.- Na+ driven in electrostatic forces and concentration gradient.- Cl- is at equilibrium.- K+ is driven in by electrostatic forces and out by concentration gradient.- Na+/K+ pump exchanges 3 Na+ inside for 2 K+ outside.Generation and Conduction of Postsynaptic Potentials- Neurotransmitters bind at postsynaptic receptors.- Chemical messengers.Sodium and Potassium ChannelsThe opening and closing of voltage activated sodium and potassium channels During three phases: rising phase, repolarization, and hyperpolarization.(When the neuron is at rest, Na+ channels are normally closed, whereas K+ is Free to enter and leave the cell.)(Given that the membrane potential is -70 mV, in what direction will the Concentration gradient make K+ move through open K+ channels? Out of thecell.)A Chemical MessageOtto Loewi (1921)-- Otto Loewi conducted an experiment with two frog hearts with the vagus nerves still attached. Both hearts were in separate petri dishes, but both dishes were filled with the same kind of fluid. As they were fresh hearts, both were still beating, so Loewi recorded the beats without any stimulation. He then stimulated Heart A, which caused it to beat slower. He recorded his findings, thentook of the fluid from Dish A and transferred it to Dish B; Heart B slowed down, like A. This was the result of acetylcholine, the first neurotransmitter discovered.Neurotransmission in Four Steps- Step 1: Synthesis and Storage—in axon terminal and cell body.- Step 2: Neurotransmitter Release. (When and action potential reaches a voltage-sensitive terminal, it opens calcium channels. Incoming calcium ions bind to calmodulin. This binds to vesicles, releasing some from filaments and inducing others to bind to presynaptic membrane and to empty their contents by exocytosis.)- Step 3: Receptor-site Activation. (Some neurotransmitter are transported from nucleus to terminal button. Others—building blocks—are imported to terminal, packaged into vesicles.)- Step 4: Deactivation of Neurotransmitters. Diffusion, Degradation, and Reuptake of glial cells.- (Neurotransmitters in the synapse are active—activity must be turned off. Reuptake—scoop neurotransmitters and recycle. Enzymatic degradation—neurotransmitters broken by


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