the 10Mf +20 kR reduces the throughput when Xc = 20K, i.e. 1/(2 X pi X .0001 X F) = 20,000. This amplifier is to amplify the pulse rate?, so its should (in theory) have a decent response down to 1/60 BpM or 1 Hz
The .47 Mf is to reduce the amplifiers gain (more negative feedback) at higher frequencies, because there is no information there, only noise. Same formula as above except this time the throughput rises (more negative feedback = less gain).
The "gain" control makes up for the probe not getting enough IR, or too much.
Frank