Chapter 45

A chemical signal operating in a paracrine manner is one that A) is active at a neuronal synapse. B) affects only the cells that synthesize the paracrine signal. C) requires transport in the blood before it can act on its target cells. D) evokes responses from all parts of the vascular system. E) must move through the air before it reaches its target cells.

A

A paracrine signal that relaxes smooth muscle cells is A) nitric oxide. B) vitamin D. C) testosterone. D) cortisol. E) antidiuretic hormone.

A

Aspirin and ibuprofen both A) inhibit the synthesis of prostaglandins. B) inhibit the release of nitric oxide, a potent vasodilator. C) activate the paracrine signaling pathways that form blood clots. D) stimulate the release of oxytocin. E) stimulate vasoconstriction in the kidneys.

A

For hormones that homeostatically regulate cellular functions, A) negative feedback typically regulates hormone secretion. B) the circulating level of a hormone is held constant through a series of positive feedback loops. C) both lipid-soluble hormones and water-soluble hormones bind to intracellular protein receptors. D) endocrine organs release their contents into the bloodstream via specialized ducts. E) it is impossible to also have neural regulation of that system.

A

Hormone X activates the cAMP second messenger system in its target cells. The greatest response by a cell would come from A) applying a molecule of hormone X to the extracellular fluid surrounding the cell. B) injecting a molecule of hormone X into the cytoplasm of the cell. C) applying a molecule of cAMP to the extracellular fluid surrounding the cell. D) injecting a molecule of cAMP into the cytoplasm of the cell. E) injecting a molecule of activated, cAMP-dependent protein kinase into the cytoplasm of the cell.

A

In a positive-feedback system where hormone A alters the amount of protein X A) an increase in A always produces an increase in X. B) an increase in X always produces a decrease in A. C) a decrease in A always produces an increase in X. D) a decrease in X always causes a decrease in A. E) it is impossible to predict how A and X affect each other.

A

Nitric oxide and epinephrine A) both function as neurotransmitters. B) both function as steroid hormones. C) are both involved in the "fight-or-flight" response. D) bind the same receptors. E) both cause a reduction in the blood levels of glucose.

A

Which category of signal exerts its effects on target cells by binding to membrane-bound receptor proteins? A) neurohormones B) estrogens C) androgens D) vitamin D E) neurohormones, estrogens, androgens, and vitamin D

A

Insect hormones and their receptors A) act independently of each other. B) are a focus in pest-control research. C) utilize cell-surface receptors only. D) are active independently of environmental cues. E) are not relevant to the study of steroid hormones.

B

Prostaglandins are local regulators whose chemical structure is derived from A) oligosaccharides. B) fatty acids. C) steroids. D) amino acids. E) nitric oxide.

B

The reason that the steroid hormone aldosterone affects only a small number of cells in the body is that A) only its target cells get exposed to aldosterone. B) only its target cells contain aldosterone receptors. C) it is unable to enter nontarget cells. D) nontarget cells destroy aldosterone before it can produce any effect. E) nontarget cells convert aldosterone to a hormone to which they do respond.

B

All hormones A) are produced by endocrine glands. B) are lipid-soluble molecules. C) are carried to target cells in the blood. D) are protein molecules. E) elicit the same biological response from all of their target cells.

C

Different body cells can respond differently to the same peptide hormones because A) different target cells have different sets of genes. B) each cell converts that hormone to a different metabolite. C) a target cell's response is determined by the components of its signal transduction pathways. D) the circulatory system regulates responses to hormones by routing the hormones to specific targets. E) the hormone is chemically altered in different ways as it travels through the circulatory system.

C

Ecdysone is a(n) A) peptide hormone. B) amine derivative. C) steroid hormone. D) iodinated protein hormone made by the thyroid gland. E) gaseous neurotransmitter.

C

Endocrine glands that are sources of steroid hormones A) secrete the steroids through ducts into the blood. B) store those hormones in membrane-bound vesicles. C) have a very short latency between steroid synthesis and steroid release. D) are all controlled by the autonomic nervous system. E) operate independently of other hormonal cuing systems

C

When a steroid hormone and a peptide hormone exert similar effects on a population of target cells, then A) the steroid and peptide hormones must use the same biochemical mechanisms. B) the steroid and peptide hormones must bind to the same receptor protein. C) the steroid hormones affect the synthesis of effector proteins, whereas peptide hormones activate effector proteins already present in the cell. D) the steroid hormones affect the activity of certain proteins within the cell, whereas peptide hormones directly affect the processing of mRNA. E) the steroid hormones affect only the release of proteins from the target cell, whereas peptide hormones affect only the synthesis of proteins that remain in the target cell.

C

A cell with membrane-bound proteins that selectively bind a specific hormone is called that hormone's A) secretory cell. B) plasma cell. C) endocrine cell. D) target cell. E) regulatory cell.

D

Suppose that substance X is secreted by one cell, travels via interstitial fluid to a neighboring cell, and produces an effect on that cell. All of the following terms could describe this substance except A) paracrine signal. B) neurotransmitter. C) prostaglandin. D) pheromone. E) growth factor.

D

Hormones that promote homeostasis A) are not found as members of antagonistic signaling mechanisms. B) travel to target cells without passage in the plasma. C) utilize receptors that bind any hormone. D) initiate signal transduction in the target cell without binding to receptors. E) usually operate as part of a negative feedback system.

E

Testosterone is an example of a chemical signal that affects the very cells that synthesize it, the neighboring cells in the testis, along with distant cells outside the gonads. Thus, testosterone is an example of A) an autocrine signal. B) a paracrine signal. C) an endocrine signal. D) both an autocrine signal and a paracrine signal. E) an autocrine signal, a paracrine signal, and an endocrine signal.

E