The nose has access to the brain.

[Guest guest]

Tiny Inhaled Particles Take Easy Route From Nose To Brain In a continuing effort to find out if the tiniest airborne particles pose a health risk, University of Rochester Medical Center scientists showed that when rats breathe in nano-sized materials they follow a rapid and efficient pathway from the nasal cavity to several regions of the brain, according to a study in the August issue of Environmental Health Perspectives.

http://www.sciencedaily.com/releases/2006/08/060802235946.htm

[sometime back we had a discussion in the group where members expressed surprise that ayurveds often use medicines through the nose to access the brain - Jagannath]