The generation of electrical signal
s in neuron
s requires both selective membrane permeability
and specific ion concentration gradient
s across the plasma membrane
. The membrane protein
s that give rise to these two essential conditions are called ion channels and pumps, respectively. Ion channels have pores that allow particular ion
s to diffuse across the neuronal membrane. Some channels also have specialized domains that sense the electrical potential
across the membrane. Such channels open or close in response to the level of membrane potential, allowing the membrane permeability to be voltage-sensitive. Pumps are membrane proteins that produce and maintain ion concentration gradients. The Na+
pump, which regulates the intracellular concentrations of Na+
by hydrolyzing ATP
to fuel the movement of these ions across the plasma membrane, is the best-known example.
From the perspective of neural signaling, pumps and channels are complementary: pumps create the concentration gradients that impel ions to diffuse through open channels, thus generating electrical signals.
Neuroscience, Sinaur Associates (QP355.2.N487 1997)