Detecting Curves using a Hough Transformation

Hello, I am trying to detect two curves of an image I am analyzing and extrapolate the curves to result in two known equation. I am finding that the matlab function for hough transforms and hough lines is only working on the straight lines I have in my image. Is there a way to find curves instead of only straight lines? Note: I have already tried to find the imfindcircles function and the shapes are not recognized as they are more like an elliipse. Thank you.

[Cam Salzberger]

Hello Tanya, can you post an example image, and the code you have tried on the Hough transform?