An ATP molecule acts as a chemical battery that receives energy from food and transfers it as needed to the cells of the body so they can do their work. “Every molecule of ATP is like a tiny battery in that it stores up energy and then releases it to power all the activities required by your cells—and indeed by all cells, in plants as well as animals” (190). ATP molecules recycle constantly, some 200 trillion trillion times a day, effectively an amount equal to the weight of the entire body.

The cerebrum “fills most of the cranial vault and is the part that we normally think of when we think of ‘the brain” (51). It is divided into left and right hemispheres, each side further divided into lobes. Behind the forehead are the frontal lobes, which deal with thought and personality; above and behind them are the parietal lobes, which handle bodily sensations; below the parietals are the temporal lobes, which deal with sound and language; in the back of the cerebrum are the occipital lobes, which take care of visual inputs.