Understanding the Brain

Inside the skull

Under the scalp and the skull, a tough membrane (the dura) surrounds the brain. Beneath the dura, cerebrospinal fluid (CSF) cushions the brain and circulates in the subarachnoid space. Arteries carry oxygen-rich blood and nutrients throughout the brain. Without this blood, brain tissue quickly dies. The brain is made up of about 100 billion cells called neurons. These neurons allow the brain to do its many jobs.

Not pictured here is the forebrain. This part of the brain contains the thalamus, hypothalamus, and pituitary gland. The thalamus sends impulses from the sense organs to the cortex. The hypothalamus controls hunger, thirst, temperature, aggression, and sex drive. It also controls the pituitary gland, which controls the secretion of many hormones.