Why does repolarization occur

Learn about the different components and functions of the human circulatory system dealt with in detail in this tutorial. The lymphatic system is also elucidated elaborately here Read More. Neurons generate electric signals that they pass along to the other neurons or target tissues. In this tutorial, you will find the basic structure of a neuron, the different classes of neurons, and membrane potentials.

It also includes the structure of the nervous system Skip to content Main Navigation Search. Third, the cells need to have protein pumps in the membrane that can move electrically charged molecules to one side, storing one type of molecule on this side and another type on the other side.

A cell becomes polarized by moving and storing different types of electrically-charged molecules on different sides of its membrane. An electrically charged molecule is called an ion. Neurons pump sodium ions out of themselves, while bringing potassium ions in.

At rest — when the cell is not sending an electrical signal to other cells — a neuron has about 30 times more sodium ions on its outside than inside; the opposite applies to potassium ions. The inside of the cell also contains molecules called organic acids. These acids have negative charges on them, so they add to the negative charge inside the cell. A neuron communicates with another neuron by sending an electrical signal to its fingertips, which causes the fingertips to release chemicals that stimulate a neighboring cell.

Known as postsynaptic potential, this electrical signal and type of potential defines a graded depolarization of the membrane. If it is large enough, it will trigger an action potential. Action potentials happen when the neuron opens protein channels in its membrane. These channels allow sodium ions to flow from outside the cell into the cell.

When the membrane potential of the axon hillock of a neuron reaches threshold, a rapid change in membrane potential occurs in the form of an action potential. This moving change in membrane potential has three phases. First is depolarization, followed by repolarization and a short period of hyperpolarization. These three events happen over just a few milliseconds. Action potential : A. Schematic and B.

The action potential is a clear example of how changes in membrane potential can act as a signal. The propagation of action potential is independent of stimulus strength but dependent on refractory periods.