The basis for this barrier is that the main component of the membrane is phospholipids, which have both polar and non-polar regions. Channel Proteins 1. A predominant type of membrane channel found in neurons, called ion channels , have pore-sizes that allow particular ions to pass through, but not larger, organic molecules. An important property of some ion channels is their ability to open and close, called gating , in response to specific stimuli. Ion Pumps 1.
Ion pumps are membrane proteins that serve both as an enzyme and a channel.
When concentration differences exist, there is a net molecular movement from a region of high conc. All ions in the body exist in different concentrations inside vs. outside cells i.e., ions have concentration gradients across cells 4. Because ions are charged, they can also be made to move by an electrical field. There are electrically charged ions in solution on either side of the neuronal membrane. Ions can cross the membrane only by way of protein channels.