Lecture 16 Bioelectricity I

Lecture 16 Bioelectricity I - Bioelectricity I What is...

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Bioelectricity I - What is electricity? - Brief History - Electrical Basis of Life
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What is electricity? Basics of electricity and electric potential What about bio-electricity?
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What is electricity? Movement of electrons. By convention (meaning Ben Franklin’s mistake), current flows opposite from electron flow. Current flow Electron flow + + + + + - - - - -
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Ben Franklin
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Electricity Electrical Potential
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Electricity Electrical Potential - + Resistance + + +
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Basic Components of Electricity Electrical Quantity Mechanical Analog Voltage [V] Pressure Current [I] Flow[Q] Resistance [R] Resistance [R] P2 P1 Q R
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Governing Relationship Ohm’s Law: V= I*R
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The Underlying Basis of Bioelectricity? Movement of Ions!
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The Discovery of Bioelectricity Rene Descartes (1596-1650) - philosopher. Why does a man move his hand back from a flame? “The flame that burns the hand is transmitted along the nervous system to the brain as a stimulus, where it torments man as a small flame.“
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R eflex arc Pain is sensed. An electrical signal passes to the CNS. A programmed reflex activates motor nerves. An electrical signal passes down the motor nerves. Muscles are activated.
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Luigi Galvani (1737-1798) Alessandro Volta (1745-1827) The Discovery of Bioelectricity
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The Galvanometer 1848, half a century after Galvani's discovery… H Bois-Reymond (1818-1896) used a modified galvanometer to detect what he called "action current" in the frog's nerve.
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Bioelectricity Ions How they move How the Nernst potential is calculated How the membrane potential is calculated
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How are ions distributed in vs out of cells? - - -- - - - - - - 4 – inside vs. 2 – outside 2 – inside vs. 4 – outside Membrane potential - Membrane potential + Hyperpolarized Depolarized Why is there more charge inside or outside of a cell? Outside Cells Inside
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Ions have charge. Inside and outside of a cell are separated by a membrane. If the ion CAN move across the membrane, then it contributes to the membrane potential. What determines which way an ion will move? The number of ions inside and outside determine charge. Na + K + Na + K + Cl - Cl- A -
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The electrochemical potential determines which way ions move. Na + K + Na + K + Cl - Cl- A - Electrical Flux (drift) If more – ions inside, then – ions will exit and + ions will enter…if they can. Diffusion (chemical) If more K inside, then K will exit, if it can.
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How do we determine the diffusion?
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This note was uploaded on 11/28/2011 for the course BME 100 taught by Professor Dr.frame during the Spring '11 term at SUNY Stony Brook.

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Lecture 16 Bioelectricity I - Bioelectricity I What is...

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