Chapter 45

Which statement is accurate? (A) Hormones that differ in effect reach their target cells by different routes through the body. (B) Pairs of hormones that have the same effect are said to have antagonistic functions. (C) Hormones are often regulated through feedback loops. (D) Hormones of the same chemical class usually have the same function.

The hypothalamus (A) synthesizes all of the hormones produced by the pituitary gland. (B) influences the function of only one lobe of the pituitary gland. (C) produces only inhibitory hormones. (D) regulates both reproduction and body temperature.

Growth factors are local regulators that (A) are produced by the anterior pituitary. (B) are modified fatty acids that stimulate bone and cartilage growth. (C) are found on the surface of cancer cells and stimulate abnormal cell division. (D) bind to cell-surface receptors and stimulate growth and development of target cells.

Which hormone is correctly paired with its action? (A) oxytocin-stimulates uterine contractions during childbirth (B) thyroxine-inhibits metabolic processes (C) ACTH-inhibits the release of glucocorticoids by the adrenal cortex (D) melatonin-raises blood calcium level

Which of the following is the most likely explanation for hypothyroidism in a patient whose iodine level is normal? (A) greater production of \(\mathrm{T}_{3}\) than of \(\mathrm{T}_{4}\) (B) hyposecretion of TSH (C) hypersecretion of MSH (D) a decrease in the thyroid secretion of calcitonin

In a short essay (100-150 words), discuss the role of hormones in an animal's responses to changes in its environment. Use specific examples.

The frog on the left was injected with MSH, causing a change in skin color within minutes due to a rapid redistribution of pigment granules in specialized skin cells. Using what you know about neuroendocrine signaling, explain how a frog could use MSH to match its skin coloration to that of its surroundings.