# What increases the surface area of the cerebrum?

The surface of the brain has wrinkles. The sulci are the inner folds of the surface of the cerebrum, and the gyri are the "bumps" of the surface. These increase the surface area of the cerebrum.

### What happens to the surface area and volume ratio as the cell decreases in size?

The ratio of surface area to volume increases. The area of a sphere is proportional to its radius squared. Volume is proportional to radius cubed. As the radius increases, the volume increases more than the surface area. As the radius decreases, the volume decreases more than the surface area, so the ratio of surface area to volume increases.

### Why is the cerebrum so highly folded?

The folds, or sulci, of the cerebrum allows the cerebral cortex to have more surface area and therefore more brain cells, or neurons, that make up the brains mass. Cognitive function seems to be related to the surface area of the cerebrum. Convolutions increase the surface area. Animals with less convoluted cerebra have lower intelligence than those with more. As an example, 'possum brains are nearly smooth.

### What is the relationship between the surface area and the volume of a cell as one increases or decreases so does the other?

Remember that as the diameter of a spherical cell increases, the surface area increases as the square of the diameter, and the volume increases as the cube of the diameter, so volume increases much faster than surface area. The same principle applies for other shapes than spherical cells, but the math is more complicated.