1 / 30

Neural Signaling: The Membrane Potential

Neural Signaling: The Membrane Potential. Lesson 9. Membrane Structure. Barrier Compartmentalization Semipermeable selectively leaky Fluid Mosaic Model Phospholipids Proteins ~. Phospholipid Bilayer. Hydrophilic heads  (phosphate) Hydrophobic tails  (lipid). Membrane Proteins.

johana
Télécharger la présentation

Neural Signaling: The Membrane Potential

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Neural Signaling:The Membrane Potential Lesson 9

  2. Membrane Structure • Barrier • Compartmentalization • Semipermeable • selectively leaky • Fluid Mosaic Model • Phospholipids • Proteins ~

  3. Phospholipid Bilayer Hydrophilic heads  (phosphate) Hydrophobic tails  (lipid)

  4. Membrane Proteins • Channels • Pumps • active transport • Receptor protein sites • bind messenger molecules • Transducer proteins: • 2d messenger systems • Structural proteins • form junctions with other neurons ~

  5. Membrane Proteins: Ionophores • Ion Channels • Non-gated • always open • Gated • chemically-gated • electrically-gated • mechanically-gated ~

  6. Chemically-Gated Channels • ligand-gated • Ionotropic • receptor protein = channel • direct control ---> fast • Metabotropic • second messenger system • indirect ---> slow ~

  7. Membrane Proteins OUTSIDE INSIDE

  8. Metabolic pumps: Active Transport • Membrane proteins • Pump ions • require energy • Na+ - K+ • Ca++ (calcium) • Also various molecules • nutrients • neurotransmitters ~

  9. Biolelectric Potential • Communication within neuron • electrical signal • electric current = movement of electrons • Bioelectric: movement of ions ~

  10. Ion Distribution • Particles / molecules • electrically charged • Anions • negatively charged • Cations • positively charged ~

  11. Ion Distribution • Anions (-) • Large intracellular proteins • Chloride ions Cl- • Cations (+) • Sodium Na+ • Potassium K+ ~

  12. Cl- Na+ + + + + + + + + + + + + + + K+ + + + + + + + + - - - - - - - - - - - - - - - - - - - - - - K+ Cl- Na+ Resting Membrane Potential outside Membrane A- inside

  13. Membrane is polarized • more negative particles in than out • Bioelectric Potential • like a battery • Potential for ion movement • current ~

  14. Bioelectric Potential POS NEG OUTSIDE INSIDE

  15. Forces That Move Ions • Concentration (C) • particles in fluid move from area of high to area of low concentration • diffusion, random movement • Electrostatic (E) • ions = charged particles • like charges repel • opposite charges attract ~

  16. Equilibrium Potential • Also called reversal potential • Distribution of single ion across membrane • e.g., EK+, ENa+, ECl- • Potential for movement of ion if channel opens • units millivolts (mV) • Potential outside = 0, by convention ~

  17. Equilibrium Potential • R = gas constant • F = Faraday constant • T = temperature (K) • Z = valence (charge) of ion ~

  18. K+: z = +1 Cl-: z = -1 Mg++: z = +2 Equilibrium Potential

  19. Equilibrium Potential • Constants never change • Assume 25 oC (298 oK) • Use log10 ~

  20. Equilibrium Potential

  21. Membrane Potential • Net bioelectric potential • for all ions • units = millivolts (mV) • Balance of both gradients • concentration & electrostatic • Vm = -65 mV • given by Goldman equation ~

  22. Membrane Potential: Goldman Equation • P = permeability • at rest: PK: PNa: PCl = 1.0 : 0.04 : 0.45 • Net potential movement for all ions • known Vm:Can predict direction of movement of any ion ~

  23. Organic anions - Membrane impermeable Opposing electrical force not required Vm = -65 mV A- C

  24. Chloride ion Cl- C • Concentration gradient equal to electrostatic gradient. • Leaks out neuron • ECl- = - 65 mV ~ Vm = -65 mV E

  25. Potassium ion E • Concentration gradient greater than electrostatic gradient. • Leaks out neuron • EK = - 75 mV ~ Vm = -65 mV K+ C

  26. Na+ Sodium ion C E • Concentration gradientandelectrostatic gradient into neuron. • ENa+ = +55 mV ~ Vm = -65 mV

  27. Metabolic Pumps • Active Transport mechanisms • Require energy • Move materials against gradient • Na+ - K+ • Calcium - Ca++ • Nutrients, etc.~

  28. Na+ - K+ Pump • Moves ions against gradients • Pumps 3 Na+ out of cell • 2 K+ into cell • Maintains gradients at rest • no active role in signalling • Energy = ATP ~

  29. Na+ Na+ Na+ K+ K+ Inside Outside Na+ Na+ Na+ K+ K+ ATP

  30. Na+ Na+ Na+ Inside Outside K+ K+ K+ K+

More Related