Final answer:
True. Gyri are the rounded ridges made by sheets of nerve cells on the cerebral cortex, which facilitate higher brain functions and increase the brain's surface area for more gray matter.
Step-by-step explanation:
True. The gyri are indeed sheets of nerve cells that produce rounded ridges on the surface of the cerebral cortex. The cerebral cortex itself is enveloped in a layer of gray matter that is crucial for the higher functions of the nervous system, such as memory, emotion, and consciousness.
The surface of the cortex is characterized by a pattern of folds—gyri (the ridges) and sulci (the grooves). These folds and grooves are significant as they increase the amount of gray matter that can fit within the cranial cavity and provide important anatomical landmarks that divide the brain into different functional areas or lobes.
For example, the central sulcus separates the frontal and parietal lobes, while the lateral sulcus delineates the boundary between the temporal lobe and other regions. The folding pattern of the cortex thus indicates specific regions of the cerebral cortex, which have implications for neurological function.