Importantly, the chemical composition of the inside of the cell and the outside of the cell are very different. Specifically, there is a difference in the concentration of sodium and potassium salts, with sodium being much higher on the outside, and potassium being much higher on the inside. When a nerve is called upon to transmit an electrical signal, a sudden movement of these salts from one side of the cell s membrane to the other occurs. This movement spreads like a wave from one end of the nerve to the other, until it reaches the end. At this point, the nerve s signal may be transmitted to the next nerve cell either by a direct extension of this process, or, more commonly, by releasing a special chemical called a neurotransmitter.
Neurotransmitters generally have one of two special functions.
In some cases, overactivity of excitatory neurotransmitters or underactivity of inhibitory neurotransmitters may lead to seizure activity by allowing an uncoordinated flow of electrical activity in the brain. Interestingly, certain areas of the brain are more likely than others to be the source of a seizure. The reason for this likelihood may be that nerve cells in these areas are particularly sensitive to certain situations that can provoke abnormal electrical transmission. Examples include sensitivity to decreased oxygen levels, metabolic changes, and infection, any of which may lead to a seizure. Many types of brain abnormalities can be responsible for producing seizure activity.