A layer of cells between the blood vessels and the cells of our brains. The brain is very delicate and can’t be exposed to just anything in the blood. This barrier of cells lets oxygen and nutrients in. But it keeps out foreign substances, such as dangerous bacteria. The barrier is important, but it can also be difficult to deal with. When scientists try to make new drugs that target the brain, the blood-brain barrier often stops these drugs from getting where they need to go.
In a sentence
The blood-brain barrier may shield the brain, but a new study shows the barrier gets leaky as we age.
blood-brain barrier A barrier of tightly packed cells that carefully regulate what molecules can — and can’t — enter the brain. The barrier protects the brain from foreign substances in the blood and helps to maintain a constant environment for brain cells.
neuronor nerve cell Any of the impulse-conducting cells that make up the brain, spinal column and nervous system. These specialized cells transmit information to other neurons in the form of electrical signals.