Which class of hormones diffuses across the plasma membrane and binds receptors inside the target cell?
Steroid hormones
✓
Peptide hormones
Protein hormones
Glycoprotein hormones
Correct Answer
Steroid hormones
Steroid hormones are lipid soluble, so they cross the plasma membrane and bind receptors in the cytoplasm or nucleus, where the hormone-receptor complex alters gene transcription. Peptide hormones are water soluble and bind receptors on the cell surface. Protein hormones are also water soluble and act through membrane receptors. Glycoprotein hormones are large water-soluble molecules that likewise bind surface receptors.
Category: Hormone Mechanisms
Question 2
After a hormone binds a G protein-coupled receptor, adenylyl cyclase converts ATP into which second messenger?
Diacylglycerol
Cyclic AMP
✓
Inositol triphosphate
Cyclic GMP
Correct Answer
Cyclic AMP
Adenylyl cyclase, activated by a G protein, converts ATP into cyclic AMP, which then activates protein kinases that change cell activity. Diacylglycerol is produced from membrane phospholipids by phospholipase C, not adenylyl cyclase. Inositol triphosphate is also made by phospholipase C and releases calcium from intracellular stores. Cyclic GMP is made from GTP by guanylyl cyclase.
Category: Hormone Mechanisms
Question 3
When two hormones acting together produce a greater response than the sum of their separate effects, the interaction is described as what?
Permissive
Antagonistic
Synergistic
✓
Competitive
Correct Answer
Synergistic
A synergistic interaction occurs when two hormones with similar effects amplify each other, producing a response greater than the sum of their separate effects. Permissive describes one hormone needing another to be present before it can act fully. Antagonistic describes hormones with opposing effects, such as insulin and glucagon. Competitive is not a standard term for hormone interactions.
Category: Hormone Mechanisms
Question 4
Release of a hormone triggered directly by a change in the level of a substance in the blood, such as glucose or calcium, is what type of stimulus?
Neural
Hormonal
Mechanical
Humoral
✓
Correct Answer
Humoral
A humoral stimulus is a change in the concentration of a substance in the blood or extracellular fluid, such as rising glucose triggering insulin release. Neural stimuli come from nerve impulses, as when sympathetic neurons trigger the adrenal medulla. Hormonal stimuli are other hormones, such as TSH stimulating the thyroid. Mechanical is not one of the three standard categories of endocrine stimuli.
Category: Hormone Mechanisms
Question 5
Which hormone is made in the hypothalamus, released from the posterior pituitary, and increases water reabsorption by the kidneys?
Antidiuretic hormone
✓
Aldosterone
Atrial natriuretic peptide
Renin
Correct Answer
Antidiuretic hormone
Antidiuretic hormone is produced by hypothalamic neurons, stored in the posterior pituitary, and released when blood osmolarity rises, causing the kidneys to reabsorb more water. Aldosterone comes from the adrenal cortex and mainly increases sodium reabsorption. Atrial natriuretic peptide comes from the heart and promotes sodium and water loss. Renin is an enzyme released by the kidneys.
Category: Pituitary and Hypothalamus
Question 6
Releasing and inhibiting hormones from the hypothalamus reach the anterior pituitary through which structure?
Hypothalamo-hypophyseal tract
Hypophyseal portal system
✓
Hepatic portal system
Circle of Willis
Correct Answer
Hypophyseal portal system
The hypophyseal portal system is a network of capillaries and portal veins that carries hypothalamic hormones directly to the anterior pituitary without passing through the general circulation. The hypothalamo-hypophyseal tract is a bundle of axons that serves the posterior pituitary. The hepatic portal system carries blood from the digestive organs to the liver. The circle of Willis is an arterial ring at the base of the brain.
Category: Pituitary and Hypothalamus
Question 7
Which anterior pituitary hormone stimulates the adrenal cortex to secrete glucocorticoids?
Thyroid-stimulating hormone
Luteinizing hormone
Adrenocorticotropic hormone
✓
Growth hormone
Correct Answer
Adrenocorticotropic hormone
Adrenocorticotropic hormone (ACTH) is released in response to corticotropin-releasing hormone and stimulates the adrenal cortex to secrete cortisol and other glucocorticoids. Thyroid-stimulating hormone acts on the thyroid gland. Luteinizing hormone acts on the gonads. Growth hormone acts on many tissues, including the liver, to promote growth.
Category: Pituitary and Hypothalamus
Question 8
Excess growth hormone secreted in an adult, after the epiphyseal plates have closed, causes which condition?
Gigantism
Pituitary dwarfism
Myxedema
Acromegaly
✓
Correct Answer
Acromegaly
In acromegaly, excess growth hormone in an adult cannot lengthen bones, so bones of the hands, feet, jaw and face thicken and enlarge. Gigantism results when excess growth hormone occurs in childhood, before the growth plates close. Pituitary dwarfism results from too little growth hormone in childhood. Myxedema is a form of severe hypothyroidism.
Category: Pituitary and Hypothalamus
Question 9
Which cells of the thyroid gland secrete calcitonin?
Parafollicular cells
✓
Follicular cells
Chief cells
Oxyphil cells
Correct Answer
Parafollicular cells
Parafollicular cells, also called C cells, lie between the thyroid follicles and secrete calcitonin when blood calcium is high. Follicular cells produce the thyroid hormones T3 and T4. Chief cells are found in the parathyroid glands and secrete parathyroid hormone. Oxyphil cells are also parathyroid cells, and their function is not well understood.
Category: Thyroid and Parathyroid
Question 10
Which mineral must be obtained from the diet for the body to synthesize T3 and T4?
Iron
Iodine
✓
Calcium
Zinc
Correct Answer
Iodine
Iodine is actively taken up by thyroid follicular cells and attached to tyrosine residues of thyroglobulin to form T3 and T4. Iron is needed for hemoglobin, not thyroid hormone. Calcium is regulated by parathyroid hormone and calcitonin but is not part of thyroid hormone. Zinc is a cofactor for many enzymes but is not built into T3 or T4.
Category: Thyroid and Parathyroid
Question 11
Which disorder results when antibodies stimulate TSH receptors on the thyroid, causing hyperthyroidism?
Hashimoto thyroiditis
Addison disease
Graves disease
✓
Cushing syndrome
Correct Answer
Graves disease
Graves disease is an autoimmune disorder in which antibodies mimic TSH, overstimulating the thyroid and causing hyperthyroidism, often with goiter and bulging eyes. Hashimoto thyroiditis is an autoimmune disorder that destroys thyroid tissue and causes hypothyroidism. Addison disease is adrenal cortical insufficiency. Cushing syndrome results from excess cortisol.
Category: Thyroid and Parathyroid
Question 12
Parathyroid hormone stimulates the kidneys to produce which compound, increasing calcium absorption from the intestine?
Erythropoietin
Renin
Angiotensinogen
Calcitriol
✓
Correct Answer
Calcitriol
Calcitriol is the active form of vitamin D, and parathyroid hormone stimulates the kidneys to make it, which in turn increases calcium absorption in the small intestine. Erythropoietin is a kidney hormone that stimulates red blood cell production. Renin is a kidney enzyme that starts the renin-angiotensin-aldosterone system. Angiotensinogen is made by the liver, not the kidneys.
Category: Thyroid and Parathyroid
Question 13
Which zone of the adrenal cortex secretes aldosterone?
Zona glomerulosa
✓
Zona fasciculata
Zona reticularis
Adrenal medulla
Correct Answer
Zona glomerulosa
The zona glomerulosa is the outermost layer of the adrenal cortex and secretes mineralocorticoids, chiefly aldosterone. The zona fasciculata is the middle layer and secretes glucocorticoids such as cortisol. The zona reticularis is the innermost cortical layer and secretes androgens. The adrenal medulla is not part of the cortex and secretes epinephrine and norepinephrine.
Category: Adrenal Glands
Question 14
Which hormone is the main glucocorticoid in humans?
Aldosterone
Cortisol
✓
Epinephrine
Testosterone
Correct Answer
Cortisol
Cortisol is the principal glucocorticoid; it raises blood glucose, mobilizes fats and proteins, and suppresses inflammation during long-term stress. Aldosterone is a mineralocorticoid that regulates sodium and potassium. Epinephrine is a catecholamine from the adrenal medulla. Testosterone is an androgen produced mainly by the testes.
Category: Adrenal Glands
Question 15
Chromaffin cells of the adrenal medulla release epinephrine when stimulated by which division of the nervous system?
Parasympathetic division
Somatic motor division
Sympathetic division
✓
Enteric division
Correct Answer
Sympathetic division
Preganglionic sympathetic neurons directly stimulate the chromaffin cells of the adrenal medulla, which release epinephrine and norepinephrine as part of the fight-or-flight response. The parasympathetic division promotes rest and digestion and does not innervate the adrenal medulla. The somatic motor division controls skeletal muscle. The enteric division is the nervous network of the digestive tract wall.
Category: Adrenal Glands
Question 16
Addison disease is caused by which condition?
Oversecretion of cortisol
Oversecretion of growth hormone
Undersecretion of thyroid hormone
Undersecretion of adrenocortical hormones
✓
Correct Answer
Undersecretion of adrenocortical hormones
Addison disease results from damage to the adrenal cortex, causing too little cortisol and aldosterone, which can lead to low blood glucose, low blood sodium and darkened skin. Oversecretion of cortisol causes Cushing syndrome. Oversecretion of growth hormone causes gigantism or acromegaly. Undersecretion of thyroid hormone causes hypothyroidism.
Category: Adrenal Glands
Question 17
Which cells of the pancreatic islets secrete insulin?
Beta cells
✓
Alpha cells
Delta cells
Acinar cells
Correct Answer
Beta cells
Beta cells are the most numerous islet cells and release insulin when blood glucose rises. Alpha cells secrete glucagon, which raises blood glucose. Delta cells secrete somatostatin, which inhibits the other islet hormones. Acinar cells are exocrine cells that secrete digestive enzymes into ducts.
Category: Endocrine Pancreas
Question 18
Glucagon raises blood glucose in part by stimulating which process in the liver?
Glycogenesis
Glycogenolysis
✓
Lipogenesis
Glycolysis
Correct Answer
Glycogenolysis
Glycogenolysis is the breakdown of stored glycogen into glucose, which the liver releases into the blood when glucagon signals that glucose is low. Glycogenesis is the building of glycogen from glucose and is promoted by insulin. Lipogenesis is the synthesis of fat and is also favored by insulin. Glycolysis breaks glucose down for energy and does not add glucose to the blood.
Category: Endocrine Pancreas
Question 19
Which hormone does the pineal gland secrete?
Prolactin
Oxytocin
Melatonin
✓
Thymosin
Correct Answer
Melatonin
Pinealocytes of the pineal gland secrete melatonin, which helps regulate the sleep-wake cycle and other circadian rhythms. Prolactin is secreted by the anterior pituitary and stimulates milk production. Oxytocin is made by the hypothalamus and released from the posterior pituitary. Thymosin is secreted by the thymus.
Category: Other Endocrine Tissues
Question 20
Stretching of the heart's upper chambers by high blood volume triggers release of which hormone?
Aldosterone
Renin
Erythropoietin
Atrial natriuretic peptide
✓
Correct Answer
Atrial natriuretic peptide
Atrial natriuretic peptide is released by cardiac muscle cells of the atria when they are stretched, and it lowers blood volume and pressure by promoting sodium and water excretion. Aldosterone comes from the adrenal cortex and raises blood volume. Renin is released by the kidneys when blood pressure falls. Erythropoietin is a kidney hormone released in response to low blood oxygen.
Category: Other Endocrine Tissues