Question 1

For hormones that homeostatically regulate cellular functions,

Accepted Answer

Hormones that homeostatically regulate cellular functions are typically regulated by negative feedback. This means that as the hormone level rises, it inhibits its own secretion, leading to a decrease in hormone release. As the hormone level falls, this inhibition is removed and hormone secretion increases, leading to an increase in hormone release. This cycle helps to maintain the circulating level of the hormone within a narrow range.

Question 2

In a positive-feedback system where hormone A alters the amount of protein X,

Accepted Answer

A positive-feedback system means that an increase in A will always result in an increase in X. This increase in X will then result in an increase in A, which will continue to occur in a self-amplifying loop, causing the system to become more and more stimulated.

Question 3

During mammalian labor and delivery, the contraction of uterine muscles is enhanced by oxytocin. This is an example of

Accepted Answer

Oxytocin's role in enhancing uterine contractions during labor and delivery is an example of positive feedback loop. The release of oxytocin stimulates more contractions, which further increases oxytocin release and so on, leading to the eventual birth of the baby. This is in contrast to negative feedback systems where a stimulus leads to a response that reduces the stimulus, thereby bringing the system back to its original state. Hormones can act in an antagonistic or synergistic way with other hormones, but oxytocin's role in labor and delivery is primarily through positive feedback. Signal transduction pathways and the anterior pituitary gland may also be involved in regulating uterine contractions, but they are not the specific focus of the question.

Question 4

The autonomic nervous system includes an endocrine gland known as the

Accepted Answer

The adrenal medulla is an endocrine gland that is part of the autonomic nervous system. It secretes hormones such as epinephrine and norepinephrine, which play a role in the body's "fight or flight" response. The other options listed are not part of the autonomic nervous system.

Question 5

Iodine is added to table salt to help prevent deficiencies of an essential mineral needed for the proper function of the

Accepted Answer

Iodine is added to table salt to help prevent deficiencies of the essential mineral needed for the proper function of the thyroid glands. Iodine is a key component of thyroid hormones and a deficiency can lead to thyroid gland enlargement, goiter, hypothyroidism, and cretinism.

Question 6

The endocrine glands include the

Accepted Answer

The parathyroid glands are part of the endocrine system, as they secrete parathyroid hormone to regulate calcium levels in the blood. B, C, D, and E are not endocrine glands, as they do not secrete hormones directly into the bloodstream.

Question 7

Hormones that promote homeostasis

Accepted Answer

Hormones that promote homeostasis usually operate as part of a negative feedback system in order to maintain a stable internal environment. This means that once a certain level or condition is reached, the hormone will signal the body to stop producing or responding to the hormone in order to maintain balance.

Question 8

The increased contraction of the human uterus during labor and delivery is at least partially due to the actions of

Accepted Answer

Oxytocin is a hormone that is released by the pituitary gland during labor and delivery. It acts on the muscles of the uterus to increase their contraction strength, leading to the expulsion of the fetus.

Question 9

Prolactin stimulates mammary gland growth and development in mammals and regulates salt and water balance in freshwater fish. Many scientists think that this wide range of functions indicates that prolactin

Accepted Answer

The fact that prolactin plays similar roles in both mammals and fish suggests that it is an evolutionarily conserved hormone, meaning it has been conserved throughout evolutionary history due to its important function in various organisms.

Question 10

In a lactating mammal, the two hormones that promote milk synthesis and milk release, respectively, are

Accepted Answer

Prolactin promotes milk synthesis, while oxytocin promotes milk release (also known as the "let-down" reflex).

Question 11

Portal blood vessels connect two capillary beds found in the

Accepted Answer

Portal blood vessels connect the capillary bed in the hypothalamus to the capillary bed in the anterior pituitary. This allows for the hypothalamus to release hormones that regulate the anterior pituitary gland.

Question 12

The body's reaction to PTH (parathyroid hormone), a reduction in plasma levels of calcium, can be opposed by

Accepted Answer

Calcitonin opposes the actions of PTH by reducing plasma levels of calcium.

Question 13

Melatonin is secreted by

Accepted Answer

Melatonin is mainly secreted by the pineal gland in response to low light levels, specifically during the night.

Question 14

A necropsy (postmortem analysis) of a marine sea star that died after it was mistakenly placed in fresh water would likely show that it died because

Accepted Answer

Marine sea stars are adapted to live in a high-salinity environment and maintain their internal fluids at a higher salt concentration than their surroundings through osmoregulation. When placed in fresh water, they become hyperosmotic and lose water by osmosis to their surroundings. This loss of water can lead to disruptions in cellular processes and ultimately death. A necropsy would likely reveal signs of cellular dehydration and osmotic stress.

Question 15

Fight-or-flight reactions include activation of

Accepted Answer

The adrenal medulla is responsible for the secretion of epinephrine (also known as adrenaline), which is an important hormone for the fight-or-flight response. Option A is incorrect because the parathyroid glands are responsible for regulating calcium levels in the blood, not metabolic rate. Option B is incorrect because the thyroid gland is responsible for releasing hormones that regulate metabolism, not calcium levels in the blood. Option C is incorrect because the anterior pituitary gland is responsible for regulating many hormone functions, including sexual development and reproduction, not the fight-or-flight response. Option E is incorrect because the pancreas is responsible for regulating blood sugar levels, not reducing them during the fight-or-flight response.

Question 16

The interrelationships between the endocrine and the nervous systems are especially apparent in

Accepted Answer

Neurosecretory cells in the hypothalamus release hormones that stimulate or inhibit the release of hormones by the pituitary gland, which in turn controls many of the body's endocrine glands, including the adrenal cortex. The hypothalamus is also involved in regulating autonomic functions, such as heart rate and blood pressure, through its connections to the sympathetic and parasympathetic nervous systems. Therefore, the interrelationships between the endocrine and nervous systems are most apparent in the hypothalamus.

Question 17

Abnormally reduced somatic growth (dwarfism) can be a consequence of decreased hormone secretion from the

Accepted Answer

The anterior pituitary gland secretes growth hormone, which stimulates somatic growth. Abnormally reduced somatic growth (dwarfism) can occur as a result of decreased secretion of growth hormone. Therefore, the best choice is E, the anterior pituitary gland.

Question 18

Oxytocin and antidiuretic hormone are synthesized in the

Accepted Answer

Oxytocin and antidiuretic hormone (ADH) are synthesized in the hypothalamus and then transported to and released from the posterior pituitary.

Question 19

The hypothalamus

Accepted Answer

The hypothalamus includes neuronal cells that terminate in the posterior pituitary. The hypothalamus functions both in neuronal transmission and as an endocrine target, but not solely in these functions. It also has hormone receptors on its cells and secretes tropic hormones that act on the anterior pituitary gland.

Question 20

Most of the exchange surfaces of multicellular animals are lined with

Accepted Answer

Epithelial tissue is responsible for lining most of the exchange surfaces of multicellular animals, including the surfaces of the lungs, digestive tract, and blood vessels. This tissue is composed of tightly packed cells that form a barrier between the internal and external environment of the organism.

Quiz 32: Homeostasis and Endocrine Signaling