ionic equilibrium & rmp - drgirl

[ArchivalUser]

Can someone please, PLEASE help me understand ionic equilibrium and RMP? I am having difficulty understanding it. Please. I really would appreciate it.

[ArchivalUser]

hi drgirl

1-All cells have POLARITY ...which means the inside of the lipid bilayer membrane is less positive (hence the notion negative...even if it is not really negative) than the outside(hence the notion positive

2-Why the inside is LESS POSITIVE(NEGATIVE) than the outside ...because of less + ve ions inside than the outside...that positive ion is Potassium

3-Why the outside is MORE POSITIVE(hence positive) than the inside....because of more + ve ions outside the cell than the inside....that positive ion IS Sodium

4-For simplicity I left the other ions out of the GAME

5-Hence IF you only think the LIPID bilayer CELL membrane and if someone ask u to put positive and negative signs you would put the positive ions OUTSIDE SIDE of the cell membrane and the negative signs INSIDE side of the cell membrane

6-Now you have ELECTRICAL CHARGE across the cell membrane ...positive outside and negative inside...recall Electric charge comes in two types, called positive and negative.

7-Even if all cells HAVE POLARITY not all cells are EXCITABLE ...

8-Excitable cells are Cells generating action potentials on stimulation ...

9-What does Number 8 mean ? Excitable cells are able to change the arrangement of the ABOVE positive and negative signs(point 5) ...which means when the excitable cells are stimulated the INSIDE side of the membrane can have POSTIVE signs and the OUTSIDE side of the membrane can have the NEGATIVE SIGNS...the term for this is DEPOLARIZATION(de-is a prefix which means THE OPPOSITE OF ...hence the opposite of polarization....

10-So when these excitable cells are at REST ...the electrical charge across the cell membrane is called RESTING MEMBRANE POTENTIAL ....UR first question

11-There are two forces on an ion(in our example on potassium and sodium)...these forces are electrical (due to their CHARGE) and concentration forces(due to the relative difference in the concentration of potassium and sodium IN AND OUT of the cell)....

12-When we say IONIC EQUILBRUM( for example potassium ionic equilibrum) ...these two forces are equal but opposite ....ur second question

this is my understanding...any input appreciated

[ArchivalUser]

hi
1. in RMP 3 sodium going out and 2 potassium going in always (meaning creating -1 charge inside the cell,i.e helping repolarization and bringing the cell back to RMP.)-- Na/k pump.

2. In RESTING MEMBRANE POTENTIAL, concentration of potassium(app-135) is greater inside the cell and sodium (app-145) outside the cell. so as u said negativity inside the cell and positivity outside the cell by the help of Na/k pump.

3. when stimulated i.e(AP) sodium moves inside the cell to reach its membrane potential(i.e until its stable for example +70mV for cardiac cell) again as u mentioned,now the inside cell become more postive compare to outside(negative).---process--DEPOLARIZATION.phase 0.

4. next step is efflux of K to attain its membrane potential(ex: -90 cardiac cell)phase 4.--REPOLARIZATION.

5.the process repeats 1 through 4.

some clinical interpretation--

1.in HYPERKALEMIA condition--- depolarization will happen.(more K ions are in ECF)
2.in HYPOKALEMIA condition ---repolarization will happen.(less K ions are in ECF)


ty yeabiruh
you correlate the subject very good.

[ArchivalUser]

Thank you so much yeabiruh & sodium. Cleared things up a little bit for me. Will watch the video again and then it should all come together. Really appreciate you both for writing back. Good Luck for your exam!