Download
changes in electrical gradients n.
Skip this Video
Loading SlideShow in 5 Seconds..
Changes in electrical gradients PowerPoint Presentation
Download Presentation
Changes in electrical gradients

Changes in electrical gradients

170 Vues Download Presentation
Télécharger la présentation

Changes in electrical gradients

- - - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - - -
Presentation Transcript

  1. Changes in electrical gradients • Electrical disequilibrium • Consequences of electrical disequilibrium • Resting membrane potential • Equilibrium potential • Membrane depolarization and hyperpolarization

  2. Cell in the body are: • In chemical disequilibrium • In osmotic equilibrium • In electrical disequilibrium – few extra negative ions inside cells and their matching positive ions are outside

  3. Na+ Cl- Organic Anions K+ Na+ Cl- Organic anions K+ Distribution of main ions

  4. 3 Na+ Na+ Cl- Organic Anions K+ Na+ Cl- Organic anions K+ ATPase 2 K+ Anionic proteins are trapped Inside the cell Electrical disequilibrium across the cell membrane  membrane potential difference

  5. How does electrical charge separation occur?

  6. The cell membrane Is an insulator There are more positive charges outside and more negative charges inside

  7. Na+ Cl- Organic Anions K+ Na+ Cl- Organic anions K+ Electrochemical gradient is a combination of the electrical and chemical gradients

  8. Electrochemical gradient • Electrical gradients and chemical gradients across the cell membrane • Electrical force moves K+ into the cell (cell has more neg. charges) • Chemical gradient favors K+ to leave the cell (K+ concentration is low outside) • These forces reach a steady state

  9. Membrane Resting Potential • The voltage difference across the cell membrane when there is an electrochemical gradient at a steady state • There is a voltage difference between the inside and the outside (potential difference)

  10. The value for the resting membrane potential

  11. Membrane Potential • Vm is the membrane potential (millivolts) • Resting membrane potential for nerves and muscles is -40 mV to -90 mV • The resting membrane potential is determined by K+

  12. K+ channels are open during the resting membrane potential.

  13. If K+ channels are open.

  14. Equilibrium Potential • The membrane potential when the channels for a particular ion are open is called the equilibrium potential for that particular ion. • At EK+ the rate of ions moving in due to the electrical gradient equals the rate of ions leaving because of the concentration gradient. • EK+ is close to the resting membrane potential

  15. Factors that are important for the equilibrium potential for an ion: • Only channels for that ion are open • The charge of the ion • Concentration of the ion inside the cell • Concentration of the ion outside the cell

  16. At the equilibrium potential for Na+ Artificial cell, Na+ is leaving because the inside became + after the inward Movement of Na+

  17. Currents during resting membrane potential K+ outward current is much stronger than Na+ inward current. Lots of K+ channels are open, few Na+ channels are open at rest.

  18. Currents during resting membrane potential K+ outward current is much stronger than Na+ inward current. Lots of K+ channels are open, few Na+ channels are open at rest.

  19. The value for the resting membrane potential

  20. Membrane potential changes when channels open or close.

  21. Changes in membrane potential • Resting membrane is polarized • Depolarization positive charges move in membrane potential moves toward 0 0 mV -70 time

  22. Membrane potential changes when channels open or close.

  23. Changes in membrane potential • Repolarization membrane potential returns to polarized state (+ charges leave cell) • Hyperpolarizationmembrane potential becomes more negative than at rest (extra + charges leave the cell)

  24. During changes in membrane potential • Very few ions move to cause changes in membrane potential.

  25. Large molecules can cross in vesicles. • Cell expends metabolic energy

  26. Phagocytosis – cell engulfs a particle into a vesicle

  27. Vesicular traffic across cell membranes • Endocytosis • Pinocytosis, cell engulfs extracellular fluid • Receptor-mediated endocytosis

  28. Receptor mediated endocytosis LDL (which is a cholesterol carrier) is a ligand that enters by receptor mediated endocytosis

  29. Exocytosis • Some molecules leave a cell by exocytosis • E.g. proteins leave cells by exocytosis

  30. Integrated membrane activity during insulin secretion Resting membrane potential

  31. Integrated membrane activity during insulin secretion