How Nerves Work - Essay Example

You must be wondering how electricity is generated in the cells. Well, cells have fluid inside them and outside them which are good conductors of electricity. The cell membrane which separates the fluids is a resistor. This causes a voltage difference which is called the Transmembrane Potential. The fluid in the cell and outside has ions of Sodium and Potassium. Ions are just atoms which have extra electrons or missing electrons., so this makes them charged. The ions on both sides of the cell membrane are not equal.

There are some things called sodium-potassium exchange pumps in the cell. These pumps send out sodium ions from inside the cell and let in potassium ions from outside to inside the cell. There are lots of positively charged potassium ions inside the cell but there are more sodium ions outside, and some potassium ions too. So the charge inside the cell is not equal to the charge outside. This causes a voltage difference which scientists call Resting membrane Potential. The nerve cell membranes have some special paths for the sodium and potassium ions to move from inside to outside, and from outside to inside the cell.

These are called channels or gates. The channels which let potassium ions diffuse are leak channels. In a membrane which is resting, all the sodium gates are closed, and a few potassium gates are open. So, the sodium ions cannot go into the cell. When there is stimuli, gates in the membrane open, and sodium ions flow into the cell. This reduces the voltage across the membrane. The voltage difference becomes lesser and lesser, and finally reaches a threshold voltage. Suddenly, hundreds of sodium gates open in the membrane, and sodium ions flood into the cell.

The membrane becomes depolarized. Scientists call this Action Potential. The time for which the sodium channels (gates) are open is just a millisecond! After this for a while the channels wont open , no matter what the stimulation. This is called the refractory period. Neurons send messages to each other by using Action Potential . Action Potential follows the All-or-none Principle. Either the threshold is reached , and there is an Action Potential, or the threshold is not reached , and there is no Action Potential.

There is no half way here. If there is another stimulus during an Action Potential, it will not cause a second action potential. The potential difference along the length of the membrane is graded potential. Now the neuron has to send its message to other cells. This is done in junctions called synapses. There are trillions of synapses in our body. To form inter- connected circuits, neurons use chemicals called neurotransmitters. Acetylecholine, which sends messages from one cell to the next.

is the neurotransmitter in many synapses. These synapses are called cholinergic synapses . You have seen the picture of a neuron in your science book. The neuron has