Researchers measured prolactin and growth hormone in the blood plasma of six subjects at regular intervals over a 24-hour period. The investigators were interested in determining if the levels of these two hormones cycle over a 24-hour period. The Figure presents the results of their experiments, with the y axis values showing the amount of each hormone expressed as a percentage of the 24-hour mean value, and each point showing the average of the six subjects’ levels.
FIGURE Mean concentrations of prolactin and growth hormone in plasma, averaged for six subjects and expressed as a percentage of the average concentrations measured for the 24-hour period.
Do the results support the hypothesis that the changes in prolactin level over a 24-hour period are associated with the sleep–wake cycle?
Source: From J. F. Sassin et al. 1972. Human prolactin: 24-hour pattern with increased release during sleep. Science 177:1205–1207.
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Chapter 42 Solutions
Biology: The Dynamic Science (MindTap Course List)
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- Which of the following statements about hormones is not correct? A. The persistance of a hormone in the blood is usually of short duration.B. The time required for the onset of hormonal effects can vary C. Organ responses to hormones occur as soon as receptors are bound. D. The duration of hormone action is variable.arrow_forwardEven though they are not a hormone, prostaglandins act in a similar way. Shortly answer the following question according to the diagram. 1.Do the prostaglandins serve as a hormonal control system? If so, identify that system and explain your answer.arrow_forwardwhich of the following statements best characterizes the hormone-receptor interaction? a. receptors can have different affinities for multiple ligands b. each hormone will only interact with one type of receptor c. the hormone-receptor contact is generally irreversible d. most cells express receptors for all hormonearrow_forward
- Match these examples to the correct type of signaling Estradiol released into the blood stream, acts on the pituitary cells Oxytocin produced in hypothalamic neurons, released from axons into the blood stream in the posterior hypothalamus Epithelial cells in arterioles release nitric oxide that causes relaxation of the adjacent smooth muscle cells Insulin released from the pancreas into the blood, acting on liver cells to simulate glucose uptake Release of cytokines by a macrophage, with cytokines acting on that macrophage to stimulate its immune function A. Neuroendocrine signaling B. Autocrine C. Paracrine signaling D. Endocrine signalingarrow_forwardList the major chemical classes of hormones found in the human body. Compare and contrast the mechanism of response that each class elicitsarrow_forwardSuppose that the circulating concentration of hor-mone is 10–10 M and the Kd for binding to its receptor is 10–8M. What fraction of the receptors will have hormone bound?If a meaningful physiological response occurs when 50% ofthe receptors have bound a hormone molecule, how muchwill the concentration of hormone have to rise to elicit aresponse? The fraction of receptors (R) bound to hormone(H) to form a receptor–hormone complex (R–H) is [R–H]/([R] + [R–H]) = [R–H]/[R]TOT = [H]/([H] + Kd).arrow_forward
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