Endocrine glands release their hormones into the interstitial fluid and bloodstream rather than through ducts.
Correct Answer
True
True. Endocrine glands are ductless; their hormones diffuse into the surrounding fluid and enter the blood, which carries them to target cells throughout the body. Exocrine glands, by contrast, release secretions through ducts.
Category: Hormone Signaling
Question 2
Paracrine signals travel through the bloodstream to reach target cells in distant organs.
Correct Answer
False
False. Paracrine signals act locally on neighboring cells in the same tissue. Hormones that travel through the blood to distant targets are endocrine signals.
Category: Hormone Signaling
Question 3
A cell responds to a particular hormone only if it has receptors for that hormone.
Correct Answer
True
True. Hormones reach nearly every cell through the blood, but only cells with the matching receptor are target cells that respond. Receptor presence is what makes hormone signaling specific.
Category: Hormone Signaling
Question 4
Down-regulation is an increase in the number of a cell's receptors in response to rising hormone levels.
Correct Answer
False
False. Down-regulation is a decrease in receptor number, usually in response to persistently high hormone levels, which makes the cell less sensitive. An increase in receptors in response to low hormone levels is up-regulation.
Category: Hormone Signaling
Question 5
Most hormone secretion is regulated by negative feedback.
Correct Answer
True
True. In negative feedback, a rise in a hormone or its effect inhibits further secretion, keeping levels within a narrow range. Positive feedback, as with oxytocin during childbirth, is much less common.
Category: Hormone Signaling
Question 6
Oxytocin is produced by endocrine cells of the anterior pituitary gland.
Correct Answer
False
False. Oxytocin is produced by neurons in the hypothalamus, transported down their axons, and stored in and released from the posterior pituitary. The anterior pituitary does not make oxytocin.
Category: Pituitary and Hypothalamus
Question 7
Prolactin from the anterior pituitary stimulates the mammary glands to produce milk.
Correct Answer
True
True. Prolactin promotes development of the mammary glands and milk production after childbirth. Milk ejection from the glands is a separate action controlled by oxytocin.
Category: Pituitary and Hypothalamus
Question 8
Excess secretion of antidiuretic hormone is the cause of diabetes insipidus.
Correct Answer
False
False. Diabetes insipidus is caused by too little antidiuretic hormone or kidneys that do not respond to it, so large volumes of dilute urine are lost. Excess antidiuretic hormone causes water retention instead.
Category: Pituitary and Hypothalamus
Question 9
Growth hormone stimulates the liver to release insulin-like growth factors that promote bone and muscle growth.
Correct Answer
True
True. Many of growth hormone's growth-promoting effects are indirect, carried out by insulin-like growth factors released mainly from the liver. These factors stimulate cell division and protein synthesis in bone and muscle.
Category: Pituitary and Hypothalamus
Question 10
Thyroid hormones increase the body's basal metabolic rate.
Correct Answer
True
True. T3 and T4 raise the rate of oxygen use and ATP production in most body cells, which increases basal metabolic rate and body heat. This is why hypothyroidism causes fatigue and cold intolerance.
Category: Thyroid and Parathyroid
Question 11
Each molecule of T4 contains three iodine atoms.
Correct Answer
False
False. T4, or thyroxine, contains four iodine atoms. T3, triiodothyronine, contains three and is the more active form.
Category: Thyroid and Parathyroid
Question 12
Calcitonin raises blood calcium by stimulating osteoclast activity.
Correct Answer
False
False. Calcitonin lowers blood calcium by inhibiting osteoclasts, which reduces bone breakdown. It is parathyroid hormone that raises blood calcium.
Category: Thyroid and Parathyroid
Question 13
The parathyroid glands are embedded in the posterior surface of the thyroid gland.
Correct Answer
True
True. The small parathyroid glands sit on the back of the thyroid gland in the neck. Because of this position, they can be damaged or removed during thyroid surgery.
Category: Thyroid and Parathyroid
Question 14
The zona reticularis is the outermost layer of the adrenal cortex.
Correct Answer
False
False. The zona reticularis is the innermost layer of the adrenal cortex, lying next to the medulla. The outermost layer is the zona glomerulosa.
Category: Adrenal and Pineal
Question 15
Aldosterone increases the reabsorption of sodium by the kidneys.
Correct Answer
True
True. Aldosterone acts on kidney tubule cells to reabsorb sodium and secrete potassium. Water follows the reabsorbed sodium, which raises blood volume and pressure.
Category: Adrenal and Pineal
Question 16
Melatonin secretion falls in darkness and rises in bright light.
Correct Answer
False
False. Melatonin secretion rises in darkness and is suppressed by light, which is how the pineal gland links the sleep-wake cycle to the day-night cycle.
Category: Adrenal and Pineal
Question 17
Type 1 diabetes mellitus is most often caused by resistance of body cells to insulin.
Correct Answer
False
False. Type 1 diabetes is most often caused by autoimmune destruction of the pancreatic beta cells, so little or no insulin is produced. Insulin resistance is the hallmark of type 2 diabetes.
Category: Other Endocrine Organs
Question 18
Erythropoietin is secreted mainly by the liver when blood oxygen levels are low.
Correct Answer
False
False. Erythropoietin is secreted mainly by the kidneys in response to low blood oxygen. It stimulates red bone marrow to increase red blood cell production.
Category: Other Endocrine Organs
Question 19
The placenta secretes human chorionic gonadotropin, which maintains the corpus luteum in early pregnancy.
Correct Answer
True
True. Human chorionic gonadotropin keeps the corpus luteum secreting estrogen and progesterone until the placenta can produce enough of these hormones itself. It is the hormone detected by pregnancy tests.
Category: Other Endocrine Organs
Question 20
Growth hormone production declines with age, contributing to loss of muscle mass in older adults.
Correct Answer
True
True. As the anterior pituitary ages, its output of growth hormone decreases. Lower growth hormone levels contribute to the reduced muscle mass commonly seen in the elderly.
Category: Development and Aging