Physiology- Origin of Membrane Potentials Flashcards
Membrane potential (Em)
separation of opposite charges across the membrane (mV)
Caused by difference in conc and permeability of key ions
Difference in change ofECF and ICF- not the membrane itself
What can nerve and muscle do when excited?
produce rapid, transient changes in their membrane potential ie create action potentials
Resting membrane potential is constant in excitable and non-excitable cells at rest. T/F?
True
Extracellular conc of Na+
150mM
Extracellular conc of K+
5mM
Extracellular conc of A-
0mM
Extracellular conc of Cl-
110mM
Intracellular conc of Na+
15mM
Intracellular conc of K+
150mM
Intracellular conc of A-
65mM
Intracellular conc of CL-
7mM
Relative permeability of Na+
1mM
Relative permeability of K+
100mM in skeletal muscle
Relative permeability of
0mM
Relative permeability of
n/a
Direction of conc gradient for Na+
inward
Direction of conc gradient for K+
outward
Why it the electrical gradient for Na+ and K+ always towards the negatively charged side of the membrane?
they are both cations (positively charged)
How many more times permeable is K+ than Na+ at resting membrane potential?
100x
What type of particles is the plasma membrane impermeable to?
large, negatively charge ic proteins (A-)
What two opposing forces act on K+?
the concentration gradient (outwards)
the electrical gradient (inwards)
Equilibrium potential
when conc gradient = electrical gradient
no further net movement occurs
Equilibrium potential of K+
-90mV
Nernst equation
Eion=61log10([ion]o/[ion]i)
Equilibrium potential of Na+
+61mV
Effect of increasing permeability of an ion on tendency for that ion to drive membrane potential towards the ion’s own equilibrium potential
Increases tendency
Ek of inside of all cells at rest
negative (~-70mV on typical nerve cell)
Em=Ek. T/F?
False
due to slight inward leak of Na+ into cell
What is the single most important factor in setting Em?
K+ gradient
