valleys in the brain surface are called

______.

sulci, fissures, or both?

Give an explanation.

Both. They are equivalent terms.

Valleys in the brain surface are called sulci. To understand this, let's first discuss the structure of the brain's surface.

The outer layer of the brain is known as the cerebral cortex. It is a highly folded structure or sheet that consists of ridges and grooves. The ridges are called gyri (singular: gyrus), and the grooves are called sulci (singular: sulcus).

The sulci play an essential role in increasing the brain's surface area within the limited space of the skull. By folding and wrinkling, the brain can fit an extensive and complex network of neural connections within the available cranial space.

On the other hand, fissures are deep and prominent grooves that divide the brain into different lobes or hemispheres. They are larger and more distinct than sulci, usually separating major brain regions.

So, to answer your question, valleys in the brain surface are specifically referred to as sulci, while fissures are the prominent and deeper grooves that divide the brain into major sections.