Cancer cells and virus-infected body cells can be killed before activation of adaptive immunity by ________.
A) natural killer cells
B) T lymphocytes
C) B lymphocytes
D) pinocytosis
A) natural killer cells
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What thin membrane, continuous with the epiblast layer, secretes fluid to bathe the embryo?
A. Chorion B. Amnion C. Yolk sac D. Corona radiata
Why do some normal cells fail to respond to a chemical signal?
A) Some cells are completely without ligands. B) Signal chemicals often break down before reaching a distant target. C) Chemical signals are only delivered to specific cells. D) Some cells are completely without receptors. E) Some cells lack the necessary receptors.
Cy Dill noticed that when he traveled from his home at 1,100 ft. elevation, to hike in the forest at 8,000 ft. elevation, his respiratory rate was elevated even while he was resting. This is because
A. the partial pressure of carbon dioxide is greater at higher elevations. B. the partial pressure of oxygen is lower at higher elevations. C. the air is "thinner" at higher elevations. D. his proprioceptors were stimulating his respiratory center. E. there would be a decrease in blood pH at that altitude.
Blood pressure increases with all of the following except increased
A) cardiac output. B) peripheral resistance. C) blood volume. D) parasympathetic innervation. E) force of cardiac contraction.