In people who stand for long periods, blood tends to pool in the lower limbs and this may result in varicose veins. What causes the varicose veins?
A. An aneurysm or weak point in an artery
B. An aneurysm or weak point in a vein
C. Failure of the venous valves
D. Failure of the lymphatic valves
E. A ruptured aneurysm in a vein
C. Failure of the venous valves
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The mesoderm associated with the allantois spreads to cover the entire inside of the trophoblast. This combination of mesoderm and trophoblast is the
A) blastodisc. B) chorion. C) mesoderm. D) allantois. E) yolk sac.
Sodium-potassium pumps restore the resting membrane potential following an action potential, a process known as ____
a. repolarization b. depolarization c. hyperpolarization d. bipolarization
Gustatory information reaches the brain by way of cranial nerve
A) I. B) II. C) X. D) IV. E) IX.
The opening of more and more Na+ ion channels during depolarization
A. is the result of the sodium-potassium exchange pump. B. is an example of a positive feedback cycle. C. is possible only if K+ channels remain closed. D. is the cause of the afterpotential. E. is an example of a negative feedback cycle.