Signals emitted by QMenubar checkboxes in PyQt

I have created a MainWindow in Qt Designer and I have given checkboxes to some of the items in its dropdowns. Clearly, I can catch a triggered-signal when an item in one of the dropdowns is clicked. But, please, can anyone tell me how I can test if the click has changed the state of the respective checkbox. Only clicking on the item obviously does not always result in such a change. Does the checkbox itself emit a checked/unchecked signal each time its state changes? How can i catch such signal in Python?