Why don’t the common ions in humans (na+, k+, cl-, etc.) cluster together in cells?

The answer is because like electric charges do not attract with each other. Ions either lack or have excess electrons in their atomic structure. Ions with a positive charge are called cations. They lack electrons in their atoms so they have to pair up with negatively charged ions, called anions, because they have excess electrons. Together, they form a compound that is neutral.

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

D-no effect on the rate