Neurobiology Week of Jan 18
Neurobiology Week of Jan 18 BIO 467
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This 2 page Class Notes was uploaded by Mikayla Huber on Sunday January 24, 2016. The Class Notes belongs to BIO 467 at Arizona State University taught by Dr. Newbern in Fall 2016. Since its upload, it has received 68 views. For similar materials see Neurobiology in Biology at Arizona State University.
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Date Created: 01/24/16
Neurobiology Week of Jan 18 Jan 20 Learning Goals: 1. Understand how neurons use different types of electrical signals. 2. Be able to explain how ion flow contributes to electrical signaling. 3. Know how to use the Nernst/Goldman equations to calculate membrane potential. 4. Be able to identify the differences in membrane permeability that are linked to distinct stages of an action potential. • Resting Membrane potential (V ) m • The state that the neuronal membrane is in when no stimuli are present. + • While at rest the membrane is mostly permeable to K . • The mammalian neuronal membrane’s resting potential charge is between - 40 to -90 mV. The exact charge is determined by the relative contribution of all the ions to the membrane. This is calculated through the Goldman equation. • Goldman equation (Goldman-Hodgkin-Katz) • P x= the permeability of each specific ion • R = 8.314 Joules per Kelvin per mole (the gas constant) o • T = The absolute temperature in Kelvin (K = C + 273.15) • F = 96485 Coulombs per mole (C.mol ) (Faraday constant) • Synaptic potential • A neuronal signal that is generated due to a chemical stimuli. • Receptor potential • A neuronal signal that is linked mainly to the sensation of touch. • *Both synaptic and receptor signals will vary in strength, depending on the intensity of the stimuli. • Action potentials (spikes, impluses) + • Occur when the membrane suddenly becomes highly permeable to Na instead of K . + • They are an all or nothing wave signal (no matter the strength of the stimuli, the signal strength will not change), once a specific “threshold potential” has been breached the signal will be sent all the way to the end of the axon. They are self- sustaining and will not decay, no matter the length of the axon. Neurobiology Week of Jan 18 • • • Ohm’s Law • V = IR • V = voltage, Volts (potential energy) • I = current, amperes (movement of ions) • R = resistance, Ohms (resistance of ion movement) • Passive electrical signals • Axons cannot properly conduct signals if they are weak, small currents are called passive signals • Electrical signals • Caused by differences in the concentration of ions across the cell membranes. Moving the ions causes signals • • Chemical diffusive force • Force that drives ion from higher concentration to lower concentration through a permeable membrane down the concentration gradient. • • Electrical Forces • A local charge is generated in the membrane as ions diffuse down the concentration gradient. This causes a net charge on both sides of the cell membrane. The charge separation creates an electrical potential across the cell membrane. Very few ions are required to generate an electrical potential. • *Electrochemical equilibrium • Chemical force and electrical force are in perfect balance • • Nernst Equation • Ex = equilibrium potential for ion X • R = 8.314 Joules per Kelvin per mole (gas constant) • T = absolute temperature in Kelvin (K = C + 273.15) • z = the valence of the permeant ion • F = 96485 Coulombs per mole (C.mol ) (Faraday constant)
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