Brain, mammal, sheep - ventral view (Gross, Low)

Structure List Olfactory tract & bulb Optic tracts Other cranial nerves Brainstem

The brainstem consists of the midbrain, pons and medulla. Although each of the three regions has special features, they have certain fiber tracts in common, and each region includes nuclei of cranial nerves. The fourth ventricle is partly in the medulla and partly in the pons. For all of the above reasons, it becomes advantageous to describe these three areas together. Within the hierarchy of the vertebrate brain, the brainstem is considered the most primitive and controls such functions as respiration and blood pressure. While electrical activity of the cerebral cortex (EEG) was once considered the main criterion for brain death, today the electrical activity of the brainstem is used. Identify the three main parts of the brainstem--midbrain, pons and medulla--and as many of the cranial nerves as possible.