The relative concentration of each in the plasma membrane is partly regulated by the:

ion channels

Explanation:

The plasma membrane plays a critical role in regulating and maintaining ionic potential inside the cell, relative to ionic concentration present outside the cell. The ion channels are specific, in that they only recognize and allow particular ions to pass through and block the rest. Their opening and closing depends on the ionic potential during that time period.

you did not attach the discourse, but i assume it to be the discourse on the origin and basis of inequality among men (the original titile in french is: "discours sur l'origine et les fondements de l'inégalité parmi les hommes"), also know as "second discourse". in this discourse, jean-jacques rousseau emphasizes that private property is the basis of all inequalities.

therefore, what enabled the old regime to maintain as long as it did was private property.

after receiving a stimus, the sensory receptors send(s) signals to the appropriate area of the body.  

the must be sensory neurons.  

hope its .