26 The Physiology of Sense Organs 



gathered from the records illustrated in figure 7. For example, 

 typical all-or-none action potentials occurred, while the receptor 

 potentials were of a graded nature, their amplitude and duration 

 depending upon stimulus parameters. In addition, the impulses 



Fig. 8. Time-course and amplitude of the receptor potential 

 in the frog stretch receptor. The preparation has been treated 

 with procaine to abolish impulse activity. Upward deflection 

 monitors the degree and rate of stretch applied to the receptor 

 muscle. Electrical activity of the nerve ending is recorded 

 by the lower traces. (From Katz,^® Fig. 13B.) 



were actively propagated along the sensory axon, while the spread 

 of the receptor potential was clearly decremental. On the other 

 hand, differences between the receptor potential and the local 

 responses of the type described by Hodgkin^" are less obvious 

 and require careful consideration. Now, the current interpretation 

 of the process of impulse generation in nerve and muscle assumes 



