Changes in electrical gradients
description
Transcript of Changes in electrical gradients
![Page 1: Changes in electrical gradients](https://reader036.fdocuments.in/reader036/viewer/2022081515/56816829550346895dddbb2e/html5/thumbnails/1.jpg)
Changes in electrical gradients
• Electrical disequilibrium• Consequences of electrical disequilibrium• Resting membrane potential• Equilibrium potential• Membrane depolarization and
hyperpolarization
![Page 2: Changes in electrical gradients](https://reader036.fdocuments.in/reader036/viewer/2022081515/56816829550346895dddbb2e/html5/thumbnails/2.jpg)
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
![Page 3: Changes in electrical gradients](https://reader036.fdocuments.in/reader036/viewer/2022081515/56816829550346895dddbb2e/html5/thumbnails/3.jpg)
Na+
Cl-
Organic anions
K+
Na+
Cl-
OrganicAnions
K+
Distribution of main ions
![Page 4: Changes in electrical gradients](https://reader036.fdocuments.in/reader036/viewer/2022081515/56816829550346895dddbb2e/html5/thumbnails/4.jpg)
Na+
Cl-
Organic anions
K+
Na+
Cl-
OrganicAnions
K+
ATPase
3 Na+
2 K+
Electrical disequilibrium across the cell membrane membrane potential difference
Anionic proteins are trappedInside the cell
![Page 5: Changes in electrical gradients](https://reader036.fdocuments.in/reader036/viewer/2022081515/56816829550346895dddbb2e/html5/thumbnails/5.jpg)
How does electrical charge separation occur?
![Page 6: Changes in electrical gradients](https://reader036.fdocuments.in/reader036/viewer/2022081515/56816829550346895dddbb2e/html5/thumbnails/6.jpg)
There are more positive charges outside and more negative charges inside
The cell membrane Is an insulator
![Page 7: Changes in electrical gradients](https://reader036.fdocuments.in/reader036/viewer/2022081515/56816829550346895dddbb2e/html5/thumbnails/7.jpg)
Na+
Cl-
Organic anions
K+
Na+
Cl-
OrganicAnions
K+
Electrochemical gradient is a combination of the electrical and chemical gradients
![Page 8: Changes in electrical gradients](https://reader036.fdocuments.in/reader036/viewer/2022081515/56816829550346895dddbb2e/html5/thumbnails/8.jpg)
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
![Page 9: Changes in electrical gradients](https://reader036.fdocuments.in/reader036/viewer/2022081515/56816829550346895dddbb2e/html5/thumbnails/9.jpg)
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)
![Page 10: Changes in electrical gradients](https://reader036.fdocuments.in/reader036/viewer/2022081515/56816829550346895dddbb2e/html5/thumbnails/10.jpg)
The value for the resting membrane potential
![Page 11: Changes in electrical gradients](https://reader036.fdocuments.in/reader036/viewer/2022081515/56816829550346895dddbb2e/html5/thumbnails/11.jpg)
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+
![Page 12: Changes in electrical gradients](https://reader036.fdocuments.in/reader036/viewer/2022081515/56816829550346895dddbb2e/html5/thumbnails/12.jpg)
K+ channels are open during the resting membrane potential.
![Page 13: Changes in electrical gradients](https://reader036.fdocuments.in/reader036/viewer/2022081515/56816829550346895dddbb2e/html5/thumbnails/13.jpg)
If K+ channels are open.
![Page 14: Changes in electrical gradients](https://reader036.fdocuments.in/reader036/viewer/2022081515/56816829550346895dddbb2e/html5/thumbnails/14.jpg)
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
![Page 15: Changes in electrical gradients](https://reader036.fdocuments.in/reader036/viewer/2022081515/56816829550346895dddbb2e/html5/thumbnails/15.jpg)
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
![Page 16: Changes in electrical gradients](https://reader036.fdocuments.in/reader036/viewer/2022081515/56816829550346895dddbb2e/html5/thumbnails/16.jpg)
At the equilibrium potential for Na+
Artificial cell, Na+ is leaving because the inside became + after the inwardMovement of Na+
![Page 17: Changes in electrical gradients](https://reader036.fdocuments.in/reader036/viewer/2022081515/56816829550346895dddbb2e/html5/thumbnails/17.jpg)
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.
![Page 18: Changes in electrical gradients](https://reader036.fdocuments.in/reader036/viewer/2022081515/56816829550346895dddbb2e/html5/thumbnails/18.jpg)
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.
![Page 19: Changes in electrical gradients](https://reader036.fdocuments.in/reader036/viewer/2022081515/56816829550346895dddbb2e/html5/thumbnails/19.jpg)
The value for the resting membrane potential
![Page 20: Changes in electrical gradients](https://reader036.fdocuments.in/reader036/viewer/2022081515/56816829550346895dddbb2e/html5/thumbnails/20.jpg)
Membrane potential changes when channels open or close.
![Page 21: Changes in electrical gradients](https://reader036.fdocuments.in/reader036/viewer/2022081515/56816829550346895dddbb2e/html5/thumbnails/21.jpg)
Changes in membrane potential
• Resting membrane is polarized• Depolarization positive charges move
in membrane potential moves toward 00
-70mV
time
![Page 22: Changes in electrical gradients](https://reader036.fdocuments.in/reader036/viewer/2022081515/56816829550346895dddbb2e/html5/thumbnails/22.jpg)
Membrane potential changes when channels open or close.
![Page 23: Changes in electrical gradients](https://reader036.fdocuments.in/reader036/viewer/2022081515/56816829550346895dddbb2e/html5/thumbnails/23.jpg)
Changes in membrane potential
• Repolarization membrane potential returns to polarized state (+ charges leave cell)
• Hyperpolarizationmembrane potential becomes more negative than at rest (extra + charges leave the cell)
![Page 24: Changes in electrical gradients](https://reader036.fdocuments.in/reader036/viewer/2022081515/56816829550346895dddbb2e/html5/thumbnails/24.jpg)
During changes in membrane potential
• Very few ions move to cause changes in membrane potential.
![Page 25: Changes in electrical gradients](https://reader036.fdocuments.in/reader036/viewer/2022081515/56816829550346895dddbb2e/html5/thumbnails/25.jpg)
Large molecules can cross in vesicles.
• Cell expends metabolic energy
![Page 26: Changes in electrical gradients](https://reader036.fdocuments.in/reader036/viewer/2022081515/56816829550346895dddbb2e/html5/thumbnails/26.jpg)
Phagocytosis – cell engulfs aparticle into a vesicle
![Page 27: Changes in electrical gradients](https://reader036.fdocuments.in/reader036/viewer/2022081515/56816829550346895dddbb2e/html5/thumbnails/27.jpg)
Vesicular traffic across cell membranes
• Endocytosis– Pinocytosis, cell engulfs extracellular fluid– Receptor-mediated endocytosis
![Page 28: Changes in electrical gradients](https://reader036.fdocuments.in/reader036/viewer/2022081515/56816829550346895dddbb2e/html5/thumbnails/28.jpg)
Receptor mediated endocytosis
LDL (which is a cholesterol carrier) is a ligand that enters by receptor mediated endocytosis
![Page 29: Changes in electrical gradients](https://reader036.fdocuments.in/reader036/viewer/2022081515/56816829550346895dddbb2e/html5/thumbnails/29.jpg)
Exocytosis
• Some molecules leave a cell by exocytosis• E.g. proteins leave cells by exocytosis
![Page 30: Changes in electrical gradients](https://reader036.fdocuments.in/reader036/viewer/2022081515/56816829550346895dddbb2e/html5/thumbnails/30.jpg)
Integrated membrane activity during insulin secretion
Resting membrane potential
![Page 31: Changes in electrical gradients](https://reader036.fdocuments.in/reader036/viewer/2022081515/56816829550346895dddbb2e/html5/thumbnails/31.jpg)
Integrated membrane activity during insulin secretion