Conduction Velocity

Reference Texts

• Physiology and Electrochemistry of Nerve Fibers. Ichiji Tasaki 1982 Academic Press New York QP 363 T325 1982
• Electrical Signs of Nervous Activity. J. Erlanger and H. S. Gasser 1937/1968 University of Pennsylvania Press Philadelphia QP331 .E7 1968
• Electric current flow in excitable cells. J. J. B. Jack, D.Noble, R. W. Tsien 1975 Oxford, Clarendon Press, QP341 .J12e 1975

Mitigating Factors

• Fiber Diameter

  V = 2.5 D
  • Tasaki, p. 87 "At 24 degrees Celsius, the conduction rate, V, expressed in m/sec, and the fiber diameter, D, in um, are related by (the above formula) the correlation coefficient between the two being 0.92."
• Myelination
• Temperature
• Axoplasmic resistance
• Capacity per unit area of membrane

Formulas

• Fiber Diameter - Tasaki

  V = 2.5 D
  • Tasaki, p. 87 "At 24 degrees Celsius, the conduction rate, V, expressed in m/sec, and the fiber diameter, D, in um, are related by (the above formula) the correlation coefficient between the two being 0.92."
• Radius, resistance and capacity

  cv = sqrt(K a / 2 R_2 C_m)
  • Hodgkin and Huxley '52
  • cv : conduction velocity
  • K : 10470
  • a : radius of axis cylinder (238um)
  • R_2: specific resistance of axoplasm (35.4 Ohms)
  • C_m: capacity per unit of area of membrane (10^-6)

Example Velocities

• Non-Saltatory (no active propogation)
  • .04 m/sec or 40 um/msec Cone Axon - Hsu, Tsukamoto, Smith, Sterling 1996 (personal communication)
  • .02 m/sec or 20 um/msec Rod Axon - Hsu, Tsukamoto, Smith, Sterling 1996 (personal communication)
  • .00038 m/sec long-range Amacrine axon - Using parameters of Hsu, Tsukamoto, Smith, Sterling 1996 (personal communication)
• Saltatory (with active propogation)
  • .005-.0025 m/sec Wide-field Amacrine in salamander - Cook and Werblin (1994)
  • 18.8 m/sec calculated for giant nerve fibre in Hodgkin and Huxley (1952)
  • 21.2 m/sec measured for giant nerve fibre in Hodgkin and Huxley (1952)

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