The Resting Membrane Potential - Lecture 4 Flashcards
Fill in the blank
The Plasma membrane of all cells are _ _ _ _ _ _ _ _ _
_ _ _ _ _ _ _ _ _ _ _ _
Polarised Electrically
What is the symbol for a membrane potential?
Em
What is the definition of membrane potential?
A separation of opposite charges across the membrane.
What are the units used for membrane potentials?
Units: mV (1/1000 volt)
Is the membrane itself charged during membrane potentials?
No - Em refers to the difference in charge between the thin layers of ECF and ICF located next to the inside and outside of the membrane
Why is the Em different between different cells?
Em relies on the permeability of key ions
What is a rapid transient change in their membrane potential?
An Action potential
What cells can produce an action potential?
Nerve and muscle cells
What is a resting membrane potential?
The constant membrane potential while the cell is at rest
What ions is the cell membrane permeable to?
Potassium
Sodium - only very slightly.
What fluid is sodium found in most abundance?
Extracellular fluid - It is generally transported into the cell
What fluid is potassium found in most abundance?
Intracellular fluid
What fluid is chlorine found in most abundance?
Extracellular
How is the Em created?
Due to unequal distribution of ions and their selective movement through the plasma membrane
What is the concentration gradient of Potassium?
Out of cells
What is the concentration gradient of Sodium?
Into cells
How many more times is Potassium permeable to the membrane than sodium at the resting potential?
100 more times
What is the cell membrane impermeable to?
Large negatively charged intracellular proteins
What is the effect of Potassium movement on the Em
Inside the cell becomes more negative. Outside the cell becomes more positive
What are the two opposing forces acting on Potassium?
The concentration gradient (tending to move K+ out of the cell)
The electrical gradient (tending to move K+ into the cell)
When does Potassium movement stop?
When both electrical gradient and concentration gradient are at equilibrium
What is the symbol for the equilibrium potential of Potassium?
Ek
What value of the Ek of Potassium?
-90mV
What is the nernst equation used for?
Is it used for calculating the equilibrium potential for any given ion
What is the Nernst equation?
Eion= 61log10 [Conc ionOutside]
———————-
[Conc Ion Inside]
What occurs when sodium is transported into the cell
The Extracellular fluid becomes more negative
Inside the cell becomes more positive
Concentration gradient into the cell
What occurs as permeability to an ion increases?
There is a tendency for that ion to drive membrane potential towards the ion’s own equilibrium potential.
Is the membrane potential positive or negative at rest?
Negative
Is the membrane potential at rest close to that of K or Na ?
Closer to Potassium at rest
What is the Golman-Hodkin- Katz equation for?
It is an equation used to calculate the membrane potential of a cell - It takes into account all ions present and their permeabilities
Em = 61log10 PermxConc Ionout
————————–
PermxConcion In
In the sodium potassium pump what is the ratio of Sodium exchanged for Potassium exchanged?
3 Sodium exported
2 Potassium entering
What type of current does the Sodium Potassium pump create?
It creates a hyperpolarising current
What is the value of E (na)?
+ 61 mV
What is the value of E(k) ?
-90mV
In the pancreas what are changes in membrane potentials linked to?
Changes in Em linked to secretion of insulin from pancreatic Beta-cells.
What is the Goldman-Hodgkin-Katz equation?
Vm = Perm of ion1[Ion1Outisde] + Perm of ion2[Ion2Outside]
—————————————————————–
Perm of ion1[Ion1Inside] + Perm of ion2[Ion2Inside]
