Pull down vs bias resistor

[Unlikekurt]

Hopefully this is a simple one. 
ex) simple input circuit with a pull down resistor followed by a coupling capacitor and then a bias resistor for say a non inverting op amp stage

The pull down sets the maximum input impedance of the circuit.  But does the bias resistor impact the impedance as well?  Or does the coupling capacitor somehow isolate the input of the op amp from the pulldown?  I certainly wouldn't think so though.

Thanks

[merlinb]

The pull down sets the maximum input impedance of the circuit.  But does the bias resistor impact the impedance as well? 

Yes they are effectively in parallel, assuming your Vbias supply is decoupled.

[antonis]

A bit more complicated answer should be:

There are formed 2 sequencial voltage dividers..
1st with signal impedance & pull-down resistor and 2nd with coupling cap & bias resistor..

For a signal impedance much lower than pull-down resistor, you can safely ingore it and proceed with Merlin's answer bearing in mind not to count on pull-down resistor for HPF, formed by coupling cap & bias resistor..