Lecture 5 Flashcards
apical membrane
with microvilli faces the lumen
basolateral membrane
faces the ecf
What ensures one-way movement transporting epithelia?
polarized distribution of membrane transporters
the body as a whole is…..
electrically neutrAL
major cations
intracellular K+ and extracellular Na+
major anions
intracellular phosphate ions and extracellular chloride ions
the ECF has a slight excess of…..
cations
the ICF has a slight excess of ….
anions
law of conservation of electrical charge
net amount of charge produced in any process is zero
separating positive and negative charges….
require energy
conductor
material through which positive and negative charges can move towards one another (water)
insulator
material separating charges (membrane)
membrane potential
the electrical disequilibrium that exists between the ECF and ICF
equilibrium potential
the membrane potential that exactly opposes the conc. gradient
nernst equation
used to calculate the equilibrium potential
resting membrane potential
the membrane potential of a cell when it is not active
relative scale of electrical gradient for excitable cells
-40 to -90 mV
the resting membrane potential is due mostly to…
K+
resting cells are permeable to…
both Na+ and K+ to different degrees
cell membrane is about ….. more permeable to K+
40
What maintains concentration gradients for Na+ and K+?
Na-K ATPase
What factors influence a cell’s membrane potential?
- conc gradient (uneven distribution) of different ions across the membrane
- permeability of membrane to those ions
depolarization
if membrane potential becomes less negative than resting
repolarization
return from depolarization
hyperpolarization
membrane potential becomes more negative
