Which of the following best describes the cerebral arterial circle (circle of Willis)?
A. Formed by the superior and inferior sagittal sinuses
B. An anastomosis circling the entire cortex
C. An anastomosis surrounding the pituitary gland
D. A portal system connecting the hypothalamus with the anterior pituitary
E. A short anastomosis found in the cerebellum
Answer: C
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Which of the following activities occurs in the presence of light within the phototransduction pathway?
a. Ganglion cells stimulate bipolar cells. b. cGMP levels increase within photoreceptors. c. Bipolar cells produce graded potentials. d. Sodium channels open in photoreceptors. e. None of the above.
The "tanning" effect (darkening of the skin) that occurs when a person is exposed to the sun is due to ________.
A) melanin B) keratin C) oil D) Langerhans cells E) sweat
________ are structures that promote the upward flow of blood in leg veins by preventing backflow.
Fill in the blank(s) with the appropriate word(s).
What is primarily responsible for the development of a resting membrane potential?
a. More diffusion and active transport of cations out of the cell than into the cell b. Pumping 2 K+ ions out of the cell for every three Na+ ions pumped into the cell c. More K+ ions diffusing into the cell than there are Na+ ions diffusing out of the cell d. More anions diffusing into the cell than are diffusing out of the cell e. None of the above are primarily responsible.