During the second week, we were introduced to how the nerve cell membrane operates and how it contributes to the communication between nerve cells. The membrane consists of phospholipids and proteins. The lipids form a bilayer structure which segregates the cell organelles and the cytosol from the external environment. The membrane proteins form passages that allow electrically charged particles to transport through the membrane. These passages are called ion channels.
Ions on the opposite sides of the membrane create two gradients: a concentration gradient and an electrical gradient. Proteins in the membrane, such as ion channels and ion pumps, help to maintain these gradients at equilibrium. In equilibrium, the cytosol is slightly negatively charged in comparison to the external environment (-65 mV). Changes in the equilibrium of the ion gradients produce an action potential, which is the conduction of charge along the axon, and this is the foundation of information transfer in the nervous system.
Some nerve cells have myelin sheaths. Myelin sheath is a fatty substance that surrounds the axon of a nerve cell. Myelin sheath insulates the axon and increases the propagation speed of the action potential. Myelin can be found in both the central nervous system and peripheral nervous system. Myelin is made up of glia cells. In central nervous system, these glia cells are called oligodendrocytes, and in peripheral nervous system, they are named Schwann cells.
– Joonas & Timo