The semilunar valves open at the end of which stage of the cardiac cycle?
a. ventricular systole
b. atrial diastole
c. isovolumetric contraction
d. isovolumetric relaxation
Ans: c. isovolumetric contraction
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ADH is "synthesized" in the:
A) anterior pituitary B) posterior pituitary C) hypothalamus D) thalamus
Inappropriate or excessive immune responses to antigens are
A) immunodeficiency diseases. B) autoimmune diseases. C) allergies. D) the result of stress. E) signs of a weak system.
Why are action potentials sometimes described as being "all-or-none" in character?
A. The rate of propagation of an action potential down an axon is independent of stimulus strength. B. They are associated with an absolute refractory period. C. A supra-threshold stimulus is required to stimulate an action potential during the relative refractory period. D. An action potential occurs whenever a suprathreshold stimulus occurs, and its amplitude does not vary with the size of a stimulus, as long as the membrane is not in the refractory period. E. Action potentials are always the same size, even when ion gradients vary in size.
When energy reserves in a muscle are exhausted and lactic acid levels increase, ________ occurs.
A) an oxygen debt B) fatigue C) treppe D) tetanus E) atrophy