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Modeling Biological Membranes with Circuit Boards and Measuring Electrical Signals in Axons: Student Laboratory Exercises
Published on: January 18, 2011
Threshold behaviour of human axons explored using subthreshold perturbations to membrane potential.
David Burke1, James Howells, Louise Trevillion
1Institute of Clinical Neurosciences, Royal Prince Alfred Hospital and University of Sydney, Sydney, Australia. d.burke@med.usyd.edu.au
The Journal of Physiology
|December 3, 2008
Summary
This study reveals how human axons adjust excitability just below their firing threshold. Subthreshold stimuli influence axonal behavior, with potassium currents playing a key role in these early changes.
Area of Science:
- Neuroscience
- Computational Biology
- Biophysics
Background:
- Axonal excitability is crucial for nerve impulse transmission.
- Understanding subthreshold behavior is key to elucidating neuronal function and dysfunction.
- Previous models often focused on suprathreshold phenomena.
Purpose of the Study:
- To investigate the threshold behavior of human axons.
- To identify the ionic mechanisms underlying subthreshold excitability changes.
- To model and validate findings using computational approaches.
Main Methods:
- Recorded changes in excitability of human cutaneous afferents (median nerve) and motor axons (ulnar nerve) using subthreshold conditioning stimuli.
- Employed a computational model of the human axon to simulate observed behaviors.
- Analyzed the contribution of specific ionic currents (Na+, K+, leak currents) to subthreshold dynamics.
Main Results:
- Subthreshold depolarizing stimuli induced a decrease in axonal threshold, developing over 3-5 ms and decaying slowly.
- This behavior was reproducible in both sensory and motor axons and accurately modeled computationally.
- Modeling highlighted the significant role of leak currents and K+ currents in subthreshold excitability, even influencing early post-action potential changes.
Conclusions:
- Human axonal threshold behavior is influenced by subthreshold stimuli through mechanisms involving passive membrane properties and conventional ion channels.
- Leak currents and K+ currents are critical contributors to subthreshold excitability.
- Slow K+ currents can activate early enough to affect post-discharge excitability changes in human axons.
Related Concept Videos
01:14Action Potential
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