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Origins of the Receptor Potential 77 



Summary 



The immediate effect of most types of stimulus energy is to cause 

 an increase in the conductance of the membrane^fjAe^eceptor 

 cell or primary sensory neuroirfij-wHich it has functional access. 

 The result of such a change in the membrane characteristics is a 

 flow of ionic current which can alter the polarity of the cell. In 

 the case of depolarizing receptor currents, both sodium and 

 potassium ions are probably involved, as well as other unspecified 

 ion species. If the current is of sufficient intensity, adjacent 

 regions of the cell will be depolarized to levels below threshold, 

 and nerve impulses will be generated. 'Receptor potentials may 

 conceivably be generated by mechanisms other than increases in 

 membrane conductance; so far there is only evidence for their 

 operation in some fish sensory cells which have been implicated 

 in the detection of variations of weak external electric fields. , 



