Define vasoconstriction and vasodilation. What is the mechanism of regulation?
What will be an ideal response
Vasoconstriction is a reduction in the lumen diameter of a blood vessel due to smooth muscle contraction. Vasodilation is a widening of the lumen due to smooth muscle relaxation. Both are regulated by vasomotor nerve fibers of the sympathetic division of the autonomic nervous system and by local metabolic substances.
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What cells clean and digest debris entering the alveoli?
A) goblet cells B) type II alveolar cells C) alveolar macrophages D) type I alveolar cells
Which choice describes the countercurrent mechanism of the nephron loop?
A. Water moves into the ascending limb; sodium moves out of the ascending limb B. Water moves out of the descending limb; sodium moves out of the ascending limb C. Water moves into the descending limb; sodium moves out of the descending limb D. Water moves out of the ascending limb; sodium moves into the ascending limb
What is the main action of lysosomes?
a. promote cellular division b. repair the plasma membrane c. destroy free radicals d. produce energy for cells e. break down organic molecules
What is true about heart valves?
A) They separate atria from ventricles, and ventricles from the large arteries that leave them. B) They enforce a one-way blood flow through the heart. C) They operate passively (no active contraction required). D) They enforce a one-way blood flow through the heart, operate passively (no active contraction required), and separate atria from ventricles, and ventricles from the large arteries that leave them.