Hormones differ from other chemical messengers such as neurotransmitters in that hormones:
A) travel through the bloodstream.
B) are all in the lipid chemical family.
C) always suppress rather than stimulate a response.
D) are released through ducts.
E) cross a synapse.
Answer: A
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According to Fig. 9.6, what is a key difference between cell signaling mediated by a surface receptor, compared to that mediated by an intracellular receptor?
A. Cell-surface receptors bind to specific signaling molecules; intracellular receptors bind any signaling molecule. B. Cell-surface receptors typically bind to smaller signaling molecules than those bound by intracellular receptors. C. Cell-surface receptors bind polar signaling molecules; intracellular receptors bind nonpolar signaling molecules. D. Signaling molecules that bind to cellsurface receptors lead to cellular responses restricted to the cytoplasm; signaling molecules that bind to intracellular receptors lead to cellular responses restricted to the nucleus. E. None of these statements about cell signaling differences is correct.
The release of which hormone from the posterior pituitary causes the initial contractions of the smooth muscle in the uterus?
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Which is a characteristic of ribbon worms and flatworms?
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