24 : 4/ The Molecular Basis of Nerve Conduction 



449 



threshold, the initial current on depolarization is in the opposite direction 

 from that expected for a passive membrane. This current reverses 

 itself after a period of time. Finally, as the depolarization is reduced 



Control 



Figure 6. Simplified diagram of clamped nerve circuit. In 

 actual practice, V was read between electrodes b and e, then 

 compensated for the drop from c to e. For a pictorial sketch 

 of electrodes, see Figure 5. After A. L. Hodgkin, A. F. 

 Huxley, and B. Katz, " Current- Voltage Relation in Nerve," 

 J. Physiol. 116: 424 (1952). 



10 II 12 13 msec 



Figure 7. Records of membrane current under a voltage clamp. 

 At zero time, the membrane potential was increased by 65 mV 

 (record A) or decreased by 65 mV (record B) ; this level was 

 then maintained constant throughout the record. The inward 

 current is shown as an upward deflection. Temperature 

 3.8°G. In a passive system, the current in record B should 

 always have been outward (downward deflection). After 

 A. L. Hodgkin, A. F. Huxley, and B. Katz, " Current- Voltage 

 Relation in Nerve," J. Physiol. I 16: 424 (1952). 



