Biology Notes :
Lo1: NS
-Because more cations are leaving the cell than are entering, this causes the interior of the cell
to be negatively charged relative to the outside of the cell. The actions of the sodium potassium
pump help to maintain the resting potential, once established.
-Recall that sodium potassium pumps brings two K+ ions into the cell while removing three Na+
ions per ATP consumed. As more cations are expelled from the cell than taken in, the inside of
the cell remains negatively charged relative to the extracellular fluid.
– It should be noted that chlorine ions (Cl–) tend to accumulate outside of the cell because they
are repelled by negatively-charged proteins within the cytoplasm.
– Table 1. Ion Concentration Inside and Outside Neurons
Ion [Extracellular] (mM) [Intracellular] (mM) Ratio outside/inside
Na+ 145 12 12
K+ 4 155 0.026
Cl− 120 4 30
Organic anions (A−) — 100
– The difference in the number of positively charged potassium ions (K+) inside and outside the
cell dominates the resting membrane potential.
– Neurogenesis: the birth of new neurons,it continues into adulthood.
