When your body gets overheated. This is a negative feedback loop. The arteries/veins will dilate letting more blood pass through. Your face tends to get red because there is more blood flow towards the surface in an effort to cool off. This is also why you sweat.
cells are not the smallest unit of life because atoms are smaller than cells
First pass metabolism of a drug is said to occur when the concentration of a drug that is administered orally is significantly reduced before it reaches the systemic circulation.
First pass metabolism usually occur in the liver.
The routes of drug administration that avoid complete first pass metabolism are: sublingual, transdermal, rectal and inhalation.