Lecture 3 Flashcards
When K+ leak channels are placed…
- membrane becomes permeable to k+
- flow along an chemical gradient
- making inside more negative
- electrochemical gradient will attract k+ ions back in (opposite attracts)
The intracellular and extracellular environements are in _______ & _________ disequillibrium
- electrical
- chemical
why are ions unevenly distributed across cell membranes
- due to the selective permeability of the cell membrane to different ions
- based on the presence of ion channels and transporters in the plasma membrane
give K+ concentrations
ICF: 140mM
ECF: 4mM
give Na+ concentrations
ICF: 15mM
ECF: 145mM
give Ca2+ concentrations
ICF: 0.001mM
ECF: 1.8mM
give Cl- concentrations
ICF: 4mM
ECF: 115mM
give P concentrations
ICF: 40mM
ECF: 2mM
give protein concentrations
ICF: 4mM
ECF: 0.2mM
What is the major contributor to cell negativity?
K+
Define the resting membrane potential (RMP)
- the net charge difference between the intercellular fluid and extracellular fluid at rest
- due to the unequal distribution of ions on each side of the membrane that results in both electrical and concentration gradient
membrane potential
measured from inside the cell relative to the outside
What is the equilibrium potential
The potential where the electrical gradient opposes the concentration gradient and there is no net movement of the ion
When Vm = Ex
Equilibrium is achieved
The nernst equation calculates what
Equilibrium potential of an ion (Ex = (61/Z) log Iout/Iin)