Why must a chemical equation be balanced? how does this relate to the law of conservation of mass?

Because the law state that matter is neither created nor destroy rather it changes from one form to another therefore equation must be balanced so that reactants to be the same with the products form

The  grandmother cell  is a hypothetical  neuronthat represents a complex but specific concept or object.[1]  it activates when a person "sees, hears, or otherwise sensibly discriminates"[2]  a specific entity, such as his or her grandmother. the term was in use at least as early as 1966 amongst staff and students in the department of experimental psychology, university of cambridge, england. a similar concept, that of the  gnostic neuron, was proposed two years later