Question 1

Melatonin ____________ .

Accepted Answer

Melatonin is responsible for regulating the sleep cycle, specifically the timing and duration of sleep. It is produced by the pineal gland in the brain during periods of darkness and is inhibited by light exposure. Melatonin levels are highest at night and lowest during the day. Therefore, option A is the correct choice. Options B, C, and D are incorrect as they do not relate to the function or production of melatonin.

Question 2

At age 85, Lyle's immune system does not respond to vaccines as well as it did when he was younger. The atrophy of which endocrine gland is likely responsible for this?

Accepted Answer

The thymus is responsible for the maturation of T cells, which play a critical role in the immune response. As a person ages, the thymus gland atrophies, leading to a decrease in the production and maturation of T cells. This can result in a weakened immune response and a reduced ability to respond to vaccines.

Question 3

John tells you that cholesterol is bad and should be eliminated from your diet. You explain to him that cholesterol is important. Which of the following hormones is synthesized from cholesterol?

Accepted Answer

Testosterone is synthesized from cholesterol. Cholesterol is a precursor molecule for the synthesis of many hormones including testosterone, estrogen, and cortisol. It is also a key component of cell membranes and plays a role in various physiological processes. Therefore, eliminating cholesterol completely from the diet is not a recommended approach.

Question 4

What ion is sometimes used as a second messenger of amino acid-based hormones?

Accepted Answer

Calcium is a common ion used as a second messenger in the signaling pathways of amino acid-based hormones such as thyroid hormone and catecholamines. When these hormones bind to their receptors on the cell surface, it activates a signaling cascade that results in an increase in intracellular calcium concentration. This increase in calcium can then trigger various cellular responses such as gene expression, muscle contraction, and secretion. Chlorine, iron, and sodium are not commonly used as second messengers in these pathways.

Question 5

Johanna, a 7-year-old girl, is significantly shorter than normal for her age. Her doctor recommends treatment with a hormone before her growth plates ossify in her long bones. Which hormone is recommended?

Accepted Answer

Growth hormone is responsible for stimulating growth in the long bones before they ossify. Administering growth hormone to Johanna can potentially help her reach a normal height for her age. Thyroid stimulating hormone stimulates the thyroid gland to produce thyroid hormones, which regulate metabolism, but does not directly affect growth. Cortisol is a stress hormone produced by the adrenal gland and does not play a role in bone growth. Parathyroid hormone regulates calcium levels in the blood and bone, but does not directly affect bone growth.

Question 6

A man has been told that he is NOT synthesizing enough follicle-stimulating hormone (FSH), and for this reason he may be unable to father a child. Choose the correct statement to explain this problem.

Accepted Answer

FSH is a hormone made in the anterior pituitary gland that stimulates sperm production in the testes. Therefore, if a man is not synthesizing enough FSH, he may have difficulty producing sperm and fathering a child. Progesterone inhibits the synthesis of FSH, but this is not the issue in this scenario since the problem is with low FSH levels. Option C is also incorrect since FSH does not stimulate estrogen secretion by ovarian cells in males. Option D is incorrect as hormones made in the anterior pituitary can have a significant impact on fertility.

Question 7

Aldosterone ___________.

Accepted Answer

Aldosterone functions to increase sodium reabsorption in the kidneys, which helps maintain blood pressure and electrolyte balance in the body. It does not increase potassium concentration in the blood, is not greatly influenced by ACTH, and is not secreted by the posterior pituitary.

Question 8

Upon landing at the airport in Lagos, Nigeria, Eric feels wide awake even though the local time is 11pm. Which synthetic hormone supplement could he administer to help adjust to the new time zone?

Accepted Answer

Melatonin is a hormone that regulates sleep-wake cycles and can help adjust circadian rhythms when taken at the appropriate time. Therefore, Eric can take melatonin to help adjust to the new time zone and overcome jet lag. Glucagon, insulin, and growth hormone are not effective in adjusting circadian rhythms.

Question 9

Regulating hormones from the hypothalamus ___________.

Accepted Answer

Hormones from the hypothalamus first enter into the hypophyseal portal system, which is a specialized network of blood vessels that connects the hypothalamus to the pituitary gland, where they can then act on the various cells of the anterior pituitary to regulate hormone secretion.

Question 10

Which of the following is correctly matched?

Accepted Answer

The zona reticularis is correctly matched with gonadocorticoids, as it is the layer of the adrenal cortex responsible for producing sex hormones, or androgens, which are sometimes referred to as gonadocorticoids.

Question 11

As a result of stress, the anterior pituitary releases___________ , which stimulates release of hormones from the adrenal cortex that retain sodium and water, increase blood sugar, and begin breaking down fats.

Accepted Answer

The anterior pituitary releases adrenocorticotropic hormone (ACTH) in response to stress, which stimulates the adrenal cortex to release hormones such as cortisol, which retain sodium and water, increase blood sugar, and begin breaking down fats. ADH (choice A) is released by the posterior pituitary and regulates water balance, but is not directly involved in the stress response. Growth hormone (choice C) and thyroid stimulating hormone (choice D) may also be released by the anterior pituitary, but are not directly involved in the stress response described in the question.

Question 12

Thyroxine is a peptide hormone, but its mechanism is different from other peptide hormones. Which of the following statements is true concerning this difference?

Accepted Answer

Most peptide hormones require a second messenger, such as cAMP or calcium, to cause a response in target cells. Thyroxine, on the other hand, can enter the cell and bind directly to nuclear receptors, without the need for a second messenger.

Question 13

In circumstances where the body requires prolonged or increased levels of a hormone, the DNA of target cells will specify the synthesis of more receptors on the surface of the cells of the target organ. This is known as___________ .

Accepted Answer

Up-regulation is the process of increasing the number of receptors on target cells, which allows for increased sensitivity and responsiveness to a particular hormone. This is a cellular adaptation that occurs in response to prolonged or increased levels of a hormone in the body.

Question 14

How do glucocorticoids enable the body to deal appropriately with stress?

Accepted Answer

Glucocorticoids, such as cortisol, enable the body to deal with stress by increasing blood glucose, fatty acid, and amino acid levels, which provide energy and resources for the body to respond to the stressor. Additionally, glucocorticoids enhance blood pressure, which can improve blood flow to the muscles and organs needed for the stress response.

Question 15

A release of parathyroid hormone (PTH) will trigger ____________ .

Accepted Answer

When released, PTH stimulates the kidneys to produce and activate vitamin D, which in turn increases the absorption of calcium from the intestines.

Question 16

Dave has discovered a new lipid-soluble hormone. Which of the following is true regarding this hormone?

Accepted Answer

Lipid-soluble hormones, due to their hydrophobic nature, require transport proteins to move through the aqueous environment of the bloodstream. This contrasts with water-soluble hormones, which can travel freely in the blood.

Question 17

The effect of a hormone on a target cell may be decreased by the presence of___________ .

Accepted Answer

Antagonistic hormones bind to the same receptor as the hormone of interest and produce the opposite effect, leading to a decrease in the response of the target cell to the hormone of interest. Plasma membrane receptors, permissive hormones, and synergistic hormones do not necessarily decrease the effect of a hormone on a target cell.

Question 18

Which hormone has only one known effect: to stimulate milk production by the breasts?

Accepted Answer

Prolactin is the hormone that has only one known effect, which is to stimulate milk production by the breasts. Progesterone and estrogen are involved in the menstrual cycle and pregnancy, while oxytocin is involved in labor and delivery, as well as milk letdown during breastfeeding.

Question 19

During an afternoon class, Lisa starts to feel hungry and worries that her blood sugar level may be dropping. Which hormone is helping to prevent a drop in blood sugar level?

Accepted Answer

Glucagon is released by the pancreas when blood glucose levels are low. It stimulates the liver to convert stored glycogen into glucose, which is then released into the bloodstream to increase blood sugar levels. This helps to prevent a drop in blood sugar levels and can provide energy for the body's cells. Insulin, on the other hand, is released when blood glucose levels are high and helps to lower them by promoting glucose uptake by the body's cells. Aldosterone and thyroxine are not directly involved in regulating blood sugar levels.

Question 20

The parathyroid glands respond to which type of stimulus?

Accepted Answer

The parathyroid glands respond to humoral stimuli, which refers to changes in the levels of specific substances (such as ionized calcium) in the bloodstream. When blood calcium levels decrease below a certain threshold, the parathyroid glands secrete parathyroid hormone (PTH) to increase blood calcium levels through various mechanisms, such as stimulating bone resorption and increasing calcium reabsorption in the kidneys.

Quiz 16: The Endocrine System