How do cells regulate ion movement?
1 Answer
Biological cells regulate ion movement through their membranes and thus have an electrical aspect to their operations.
The cell membrane is composed of lipids and poses a barrier to the free flow of water soluble ions. This means it has electrical resistance, expressed in millivolts .
A pulse is sent from one end of the nerve to the other with the help of electrically charged salts that pass through ion channels in the membrane. This leads to an imbalance in electrical charge.
For a nerve cell, the thickness of the cell membrane is about 7 nm and the potential difference across it is around -70 mV in the resting state.
The start of an impulse is the opening of the sodium channels, allowing Na+ ions to flood in, changing the potential across the membrane from -70mV to +40mV.
This is followed by the closing of the sodium channels and opening of the potassium channels, dropping the potential below -70mV and then the ion concentrations are returned to the resting state by the active ion pumps.
This propagation of charged ions along the cell constitutes an electric current.
This concept is one of the hardest to understand and remember. There is so much more beyond this. One new idea is that these are not electrical but sound says Heimburg, who co-authored a new study with Copenhagen University theoretical physicist Andrew Jackson.
