Sign Up for a Free Account

This is an image preview.
Start a Free Account
to view the full image.

Sign Up for a Free Account For information on discounts, see Plans & Pricing

  • Nearly 3,000 illustrations, including video clips of neurologic disorders.

  • Every article is reviewed by our esteemed Editorial Board for accuracy and currency.

  • Full spectrum of neurology in 1,200 comprehensive articles.

  • Listen to MedLink on the go with Audio versions of each article.

Passage of substances across the blood brain barrier

(1) Passive diffusion. Fat-soluble substances dissolve in the cell membrane and cross the barrier, eg, alcohol, nicotine, and caffeine. Water-soluble substances like penicillin have difficulty in getting through. (2) Active transport. Substances that the brain needs such as glucose and amino acids are carried across by special transport proteins. (3) Receptor-mediated transport. Molecules link up to receptors on the surface of the brain and are escorted through, eg, insulin. (Contributed by Dr. K K Jain.)