Quote Originally Posted by partcleguy
Marijuana is a vasodilator which causes the blood vessels in your eyes to dilate. This basically means the blood vessels open up and become larger. I believe the red eyes are caused by being able to see so many more vessels that used to be too small to notice before smoking. The dilation is caused by the action of THC which causes the smooth muscle lining blood vessels to relax. Hope that helps :thumbsup:

Edit: yes, dry mouth is most likely caused by stimulation of the sympathetic nervous system. This is a division of the autonomic nervous system that reacts in times of stress normally, but is artificially stimulated by the THC. You can feel your sympathetic nervous system kick in when you start to run or are scared (notice sweating, dilated pupils, etc.). One of the other things is your body stops producing so much saliva... hence dry mouth
GG.