Quantal Fluctuations in Generator Potential

Abstract

A single primary sensory neurone or receptor transmits information about the intensity and time course of an applied stimulus to second order sensory neurones. This process may be idealized as a sequence: a) The stimulus directly (as in mechanoreceptors) or indirectly (as in photoreceptors) alters the properties of a specialized area of membrane, the receptor membrane, so that the receptor membrane has a changed ionic permeability and hence changed conductance. The receptor membrane has a non-regenerative I-V relation. b) This change in ionic chord conductance, together with the electrochemical gradient across the membrane, causes a current to flow across the membrane. c) This receptor current produces a change in membrane potential, the receptor potential. d) The receptor potential spreads electrotonically through the receptor terminals. The size and time course of the receptor potential depend on the size and time course of the receptor current, the membrane I-V relations and the geometry of the receptor terminals. e) The receptor potential spreads to an area of membrane which has a regenerative I-V relation – this is the spike initiating region. The electrotonic spread of the receptor potential into this region is called the generator potential. f) If the potential in the spike initiating region reaches a value where the I-V relation has a negative slope conductance intercept with the zero current axis (the threshold potential) an action potential is generated. KeywordsReceptor PotentialPhoton AbsorptionOutput EventInput EventRetinula CellThese keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.