The sympathetic nervous system will cause vasodilation in the arteries of many blood vessels, but vasoconstriction in the brain. Why does this occur?
What will be an ideal response?
Because the brain needs a relatively constant flow of blood, whether the body is at rest or under stress, it will try tomaintain a constant level of perfusion to the brain. Since the sympathetic nervous system increases heart rate, blood will flow to the brain faster than it does while at rest, so by constricting the arteries, it will decrease the amount of blood each beat that reaches the brain and thereby keeping a fairly constant amount of blood flowing to the brain.
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Athletes abuse erythropoeitin (EPO) because it
A. increases the red blood cell supply, which brings more oxygen to muscle cells. B. increases the white blood cell supply, which prevents infection. C. decreases the red blood cell supply, which brings more oxygen to muscle cells. D. increases the red blood cell supply, which depletes oxygen from muscle cells.
When placed in solution, an inorganic substance dissociates completely, forming hydrogen ions and anions. This substance would be a
A) strong base. B) weak base. C) strong acid. D) weak acid. E) salt.
How does the immune system recognize a foreign cell?
A. The presence of toll-like receptors. B. The presence of pathogen-associated molecular patterns. C. The presence of complement. D. The presence of organ-specific phagocytes.
A bee sting can trigger a massive release of histamine, which causes ________ and a(n) ________ in arterial blood pressure.
A. vasoconstriction; increase B. vasoconstriction; decrease C. vasodilation; increase D. vasoconstriction; oscillation E. vasodilation; decrease