Nearly all cells maintain a voltage difference between their interior and exterior environment. The voltage of the cell is measured in milli volts (mV). The voltage of a typical animal cell is -70 mV. In majority of cells very little voltage fluctuations are known to occur but in some cells this is a usual feature. Some cells also show up and down cycles as the voltage increases and declines. The duration of these potentials vary over a wide range. In brain cells, the up and down cycle of action potential are completed in less than thousandth of a second while in other types of cells the cycles may take several seconds. The electrical property of an animal cell is dependent upon the membrane structure. Cell membrane is made up of a layer of lipids and proteins. The lipid layer acts as an insulator.

Generation of action potential within a neuron

All animal cells are electrically polarized as they maintain a voltage difference known as membrane potential. In case of neurons, axons, dendrites and cell body have different electrical properties. The most excitable part of a neuron is the axon hillock but axon and cell body also become excited. At the axon hillock the resting potential is -70 mV and the threshold potential is -55 mV. Synaptic inputs to the neuron result in depolarization causing the membrane potential to rise or fall. Action potential is produced when enough depolarization accumulates and the membrane potential reaches a threshold value. Read more »