Capacitance and Myelination vs. Conduction Velocity Mengqi Xing, Basheer Subei, Rafael Romero.
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Transcript of Capacitance and Myelination vs. Conduction Velocity Mengqi Xing, Basheer Subei, Rafael Romero.
Capacitance and Myelination vs.
Conduction Velocity
Mengqi Xing, Basheer Subei, Rafael Romero
Membrane Thickness
• Soliton Model of Action Potentials– Soliton (mechanical wave) propagates
along membrane that causes AP– Thermodynamically sound– Δ in membrane thickness = Δ in
Capacitance• Piezoelectricity
𝐶=ε r ε 0𝐴𝑑
Myelin Distribution• Myelin sheaths– Δ membrane thickness Δ membrane
capacitance – Speed up AP propagation
• Distribution of Myelin– Nodes of Ranvier• Hodgkin-Huxley Model
–Myelination• Passive Cable Model
Methods• Testing Spatial Distribution of Myelin:– 6 Different Distributions– Control, Full, Short, Long, Mid Gap,
Multiple Gap– Scaled up axon dimensions
• Studying:– Effect of Membrane Thickness/Distribution– Significance of Nodes of Ranvier– Conductance velocity
Different Distributions
Control
Short Myelin
Full
Long Myelin
Mid Gap Multiple Gap
Control
Full Myelin
Short Myelin
Long Myelin
Mid Gap Myelin
Multiple Gap
Average Conduction Velocity
Control Multiple Gap Mid Gap Full0
1000
2000
3000
4000
5000
6000
7000
2 mA Current
Myelin Distribution
Aver
age
Velo
city
(m/s
)
Control Multiple Gap Mid Gap FullVelocity (m/s) 191.36 438.55 620.4 6049
Discussion• Main Points:–Myelination • Fast conduction BUT AP decays• No gates ∴ no current to recharge AP
– No myelination • Signal Slow• Gates throughout axon allow propagation
• Nodes of Ranvier– Recharge AP & prevent signal decay
Thanks!