Most fish exchange gases using gills on either side of the pharynx (throat). Gills are tissues which consist of threadlike protein structures called filaments. These filaments have many functions including the transfer of ions and water, as well as the exchange of oxygen, carbon dioxide, acids and ammonia.
The nervous sysyem because i looked it up on the internet. search gal stones effect which body system then but a dash .You will find that it says nervous system.
