Lecture+16+-+Neuronal+Structure%2C+Function+and+Diversity+I (1)

Lecture+16+-+Neuronal+Structure%2C+Function+and+Diversity+I (1)

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Unformatted text preview: Monday’s Class NEURONAL STRUCTURE, FUNCTION & DIVERSITY Chapter 5 pp. 154-­‐161 Chapter 4 pp. 142-­‐148 MIDTERM #1 TOMORROW •  BRING A UCD 2000 SCANTRON TO EXAM •  NO CALCULATORS NEEDED •  You may NOT wear hats or sunglasses, or use headphones or cell phones •  You may NOT speak to your classmates during the exam. •  You may NOT leave the room once the exam begins unYl aZer you turn your exam in. •  Cell phones need to be in the OFF posiYon and in your bag. If your cell phone goes off, your exam will be collected and your exam graded only to that point. No texts either. What you should be able to do by the end of today’s lecture •  Explain the nature of the membrane potenYal and the factors that influence it. •  Sketch and label a typical nerve, discuss the funcYon of each region, and appreciate the nature of diversity in neuron structure. Luigi Galvani & Frankenstein •  Luigi Galvani (1737-­‐1798) was the first scienYst to appreciate the link between electricity & animaYon (life) •  Famous frog leg experiment in 1771 demonstrated the electrical transmission of the nervous system •  RevoluYonized idea that nerves transmit electrical current & not just a canal filled with fluid •  Mary Shelley was influenced by work of Galvani & chose electricity as the animaYng force to bring Frankenstein to life Moyes & Schulte: Principles of Animal Physiology Squid Giant Axons The Physiology of Control: IntegraYon •  Animals need to funcYon like a coherent organism (not like a loose collecYon of cells & processes) •  Cellular integraYon •  Whole animal integraYon – selecYve combinaYon and processing of sensory, endocrine and central nervous system informaYon Umflint.com theruniverse.com So0pedia.com Neuronal and Hormonal signaling both convey informaYon over long distances The nervous system controls predominantly the fine rapid movements of discrete muscles. The endocrine system predominantly controls more widespread, prolonged acYviYes Any behavioral acYvity is a property of the neural circuit that mediates it Cockroach startle response Neurons •  Vary in structure and properYes •  Use same basic mechanisms to send signals Principles in Animal Physiology, Figures 4.1 (2e) & 5.2 (3e) Signal release Electrical Signals in Neurons •  Neurons have a resYng membrane potenYal (like all cells) •  Membrane potenYal is negaYve at rest Electrical Signals in Neurons –  Neurons are excitable •  Can rapidly change their membrane potenYal –  Depolariza;on – membrane potenYal becomes less negaYve –  Repolariza;on – membrane potenYal returns to resYng value –  Hyperpolariza;on – membrane potenYal becomes more negaYve than resYng value Changes in membrane potenYal act as electrical signals Principles in Animal Physiology, Figure 5.5 Gated Ion Channels •  Neurons depolarize or hyperpolarize by selecYvely altering permeability •  Gated ion channels open or close in response to a sYmulus –  Example: neurotransmiker •  Channels only allow specific ions to pass through the membrane –  Ion moves down its electrochemical gradient –  Only relaYvely small numbers of ions move across •  As permeability to a specific ion increases, membrane potenYal will approach that ion’s equilibrium potenYal (Nernst equaYon) Ion Movement •  Channels only allow specific ions to pass through the membrane –  Ion moves down its electrochemical gradient –  Only relaYvely small numbers of ions move across •  As permeability to a specific ion increases, membrane potenYal will approach that ion’s equilibrium potenYal (Nernst equaYon) •  Net movement stops when the equilibrium poten;al is reached Principles in Animal Physiology, Figure 5.4 Membrane potenYal calculaYons •  Nerst EquaYon calculates potenYal of each ion separately RT [ x ]outside Ex = ln zF [ x ]inside •  R = gas constant, T=temp (K), F = faraday constant (96,500 coulombs/gram-­‐equivalent charge), z = charge on each ion (1 or 2) € 58 [ x ]outside Ex(mV ) = log10 At room temp z [ x ]inside Membrane potenYal calculaYons •  Goldman EquaYon calculates membrane potenYal of all ions together PK [K + ] + PNa [ Na + ] + PCl [Cl− ] RT outside outside inside ENa, K , Cl = ln F PK [K + ] inside + PNa [ Na + ] inside + PCl [Cl− ] outside •  R = gas constant, T=temp (K), F = faraday constant (96,500 coulombs/gram-­‐equivalent charge), P = permeability constants •  Other ions (Ca++, Mg++, etc.) are ignored in this simplified form of the equaYon because their permeabiliYes are very low Neural Zones (e.g. Motor neuron) •  Four funcYonal zones •  1. Signal recep;on –  Dendrites and the cell body (soma) –  Incoming signal received and converted to change in membrane poten;al •  2. Signal integra;on –  Axon hillock –  Strong signal is converted to an ac;on poten;al (AP) •  3. Signal conduc;on –  Axon (some wrapped in myelin sheath) –  AP travels down axon •  4. Signal transmission –  Axon terminals –  Release of neurotransmiIer Principles in Animal Physiology, Figure 5.2 Wednesday’s Class NEURONAL STRUCTURE, FUNCTION & DIVERSITY II Chapter 5 pp. 162-­‐174 Chapter 4 pp. 142-­‐160 ...
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