Constante espacial λ
- Created by
- Renato Passos, Eng. de Software
- Reviewed by
- Renato Passos, Eng. de Software
Last updated: Apr 18, 2026
About this calculator
The spatial constant λ calculator determines the characteristic length for signal propagation in biological membranes. It uses the formula λ = √(R_m·r/(2·R_i)), where R_m is membrane resistance, r is internal axial resistance (per unit length), and R_i is total internal resistance. This formula shows how the membrane's resistance and internal conductivity affect the attenuation of electrical potentials in structures like neurons.
This calculation is critical in biophysics to study impulse conduction in neurons, muscle cells, and ion channels. For instance, in axons, λ indicates the average distance an electrical signal retains its strength before dissipating. Higher λ values mean less attenuation, often seen in cells with larger diameters or lower membrane resistance.
When using this calculator, ensure unit compatibility (e.g., ohms per unit length) and that R_m and R_i values are experimentally measured or from reliable models. Common errors include confusing R_i with membrane resistance and neglecting to standardize units before calculation.
Frequently asked questions
What units should R_m and R_i have?
R_m is typically in ohms (Ω), while R_i is in ohms per unit length (Ω/m), depending on the experimental context.
Why is R_i in the denominator?
R_i represents internal resistance. Higher R_i reduces λ because signals attenuate faster in media with higher resistance.
Does cell radius affect λ?
Yes, the radius (r) appears in the formula. Wider cells (larger r) usually have higher λ, improving signal propagation.
How is λ applied in practice?
λ predicts conduction efficiency in neurons. Cells with higher λ maintain signals over longer distances without requiring myelination.