Air entering the body is filtered, warmed, and humidified by the
A) upper respiratory tract.
B) lower respiratory tract.
C) lungs.
D) alveoli.
E) bronchioles.
Question 2
Which of the following is a sympathetic neurotransmitter used for vasodilation?
A) acetylcholine
B) norepinephrine
C) dopamine
D) serotonin
E) nitric oxide