Every living cell on Earth maintains a voltage difference across its outer membrane. In neurons, this resting membrane potential sits at approximately -70 millivolts — the inside of the cell slightly negative relative to the outside. When a neuron fires, that voltage briefly reverses. The whole thing takes about one millisecond. This process, repeated billions of times per second across the nervous system, is the physical substrate of thought, sensation, and movement.
But neurons are not unique. Every cell type — muscle cells, epithelial cells, immune cells, even bacteria and plant cells — maintains its own characteristic membrane potential. And the emerging understanding in bioelectricity research is that these voltages are not mere byproducts of cellular chemistry. They are information.
How Cells Read Voltage
The membrane potential is maintained by ion channels — protein tunnels embedded in the cell membrane that selectively allow specific ions to flow in or out. Sodium, potassium, calcium, and chloride ions carry charge across the membrane in carefully regulated patterns. Specialised voltage-gated channels open and close in response to voltage changes, creating cascading electrical signals that can propagate across cell networks.
Resting Membrane Potentials by Cell Type
- →Neurons: approximately -70 mV
- →Muscle cells: -90 mV
- →Red blood cells: -10 mV
- →Cancer cells: often depolarised, closer to 0 mV — a bioelectric signature now being studied as a diagnostic marker
What This Means For The Future
The discovery that cancer cells have characteristically depolarised membranes — and that restoring normal membrane potential can slow tumour growth in animal models — is one of the most striking findings in recent bioelectricity research. It suggests that membrane potential is not just a feature of neural function, but a fundamental control variable for cell identity and behaviour across all tissue types.
Source: Levin Lab, Tufts University · Hou et al., Nature Communications (2024)
Credit: Shubham Dhage on Unsplash