The first heart sound (lub) is:
A) the sound of ventricular muscle contracting
B) the sound of cuspid (AV) valves closing during ventricular systole
C) the sound of atrial muscle contracting
D) the sound of semilunar valves closing during ventricular diastole
Answer: B) the sound of cuspid (AV) valves closing during ventricular systole
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The central nervous system (CNS) includes the
A) brain. B) nerves and muscles. C) spinal cord. D) brain and spinal cord. E) nerves.
The anterior surface of the heart consists mostly of this chamber.
A. Right atrium B. Left atrium C. Right ventricle D. Left ventricle
Undifferentiated spermatogenic cells are called
A) primary spermatocytes. B) spermatids. C) secondary spermatocytes. D) spermatogonia.
The hormonal pathway in the reproduction of nonviviparous vertebrates is activated by
a. environmental cues. b. day length. c. pheromones. d. all of these. e. none of these.