The concentrations of two substances are increasing outside the cell. For substance A, transport into the cell increases proportionally as the concentration outside increases. For substance B transport into the cell increases but then levels off despite the concentration outside continuing to increase. What is the explanation for this?
A. Saturation
B. Affinity
C. Competition
D. Specificity
Answer: A
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How are endocrine glands and hormones involved in homeostatic reflexes?
A. Endocrine glands can be efferent pathways, and hormones can be effectors. B. They are not involved; reflexes only involve actions of the nervous system. C. Endocrine glands can be receptors, and hormones can be effectors. D. Endocrine glands can be integrating centers, and hormones can be efferent pathways. E. Endocrine glands are not part of reflex mechanisms, but hormones can be afferent or efferent pathways.
In the male, which muscle ejects urine or semen, compresses the base of the penis, and helps in formation of an erection?
A. Iliococcygeus B. Superficial transverse perineal muscle C. External urethral sphincter D. Bulbospongiosus E. Pubococcygeus
The __________ is a continuation of the central nervous system and exits the skull through the _______.
A) vagus nerve, spinal cord B) spinal cord, foramen magnum C) brainstem, vertebral foramen D) medulla, cauda equina
Which layer of a blood vessel contains smooth muscle and elastic fibers?
A) tunica intima B) tunica externa C) endothelium D) tunica media