i beg to differ

My Human Physiology book reads:
"Sleep is an easily reversible state of inactivity characterized by lack of interaction with the external environment."
--> so THAT's why I've overslept the past coupla days.

Other honourable mentions:
Did You Know?
Olfactory information is the only sensory information that isn't passed through the thalamus (in the brain). Odorant receptors (G protein-cAMP-coupled membrane proteins) project directly into the olfactory cortex and to the amygdala and hippocampus (parts of the limbic system involved with emotion and memory).

The Human Body's Believe It Or Not
"Taste is a combination of 5 sensations: sweet, sour, salty, bitter and umami."

Umami?