A heart attack can best be described as:
a. a sudden, harmful contraction of the heart muscles.
b. an invasion of heart tissue by pathogens such as bacteria.
c. a death of cells in the heart brought about by blockage of a coronary artery.
d. a failure of the nervous system to bring about heart contractions.
e. a rapid, harmful expansion of blood volume supplied by the heart.
Blood returns to the heart (select all that apply):
a. through capillaries feeding into venules.
b. through venules feeding into arteries.
c. by force of contractions of the heart’s left ventricle.
d. by force of contractions of the heart’s right ventricle.
e. by force of skeletal muscle contractions.
The small size of alveoli, coupled with their large numbers, provide the lungs with what critical quality for gas exchange?
a. a resistance to damage caused by pollutants
b. an affinity for oxygen and lack of affinity for carbon dioxide
c. an affinity for carbon dioxide and lack of affinity for oxygen
d. a large surface area
e. a small surface area
Two promising means of using components of the immune system to fight disease have begun to develop in recent years. One of them employs the cells whose natural function is to limit immune system attacks, ________; the other stimulates or suppresses the ________ that are the initial sensors of microbial infection.