Endocrine System and Hormones Practice Quiz (23 questions)

1. How do endocrine glands deliver their secretions to tissues throughout the body?

A. They send hormones through specialized ducts to organs

B. They discharge hormones into the digestive tract for absorption

C. They transmit hormones along neurons to nearby target cells

D. They release hormones directly into the bloodstream

Answer: (D)

Explanation

Endocrine glands release hormones directly into the blood, allowing circulation to distribute them throughout the body. Ducts are characteristic of exocrine glands, not endocrine glands.

2. What best describes a hormone in the endocrine system?

A. A chemical messenger that produces a specific effect in a target cell or organ

B. A receptor protein that detects signals at the surface of a target cell

C. A tissue response that occurs after a target organ is stimulated

D. A glandular structure that releases products into a surrounding duct

Answer: (A)

Explanation

A hormone is a chemical messenger transported to target cells or organs, where it produces a specific effect. A target cell or organ responds to the hormone rather than producing the definition of the hormone itself.

3. What did Berthold’s 1849 rooster experiment suggest about the testes?

A. They affect feathers and body size through secretions released into the digestive system

B. They release a substance into the bloodstream that influences body and reproductive traits

C. They control rooster behavior through nerve connections extending directly to the brain

D. They produce physical changes only when attached to muscles by functioning nerves

Answer: (B)

Explanation

Berthold found that transplanted testes restored typical rooster traits despite lacking nerve connections, suggesting that a testicular substance entered the bloodstream. The finding therefore supported chemical rather than direct neural communication.

4. How does a lipid-soluble hormone such as cortisol typically affect a target cell?

A. It diffuses through the membrane and binds to an intracellular receptor

B. It attaches to a duct protein that carries the hormone into the cytoplasm

C. It enters the bloodstream and is converted into a water-soluble neurotransmitter

D. It remains outside the membrane and binds to a receptor on the cell surface

Answer: (A)

Explanation

Lipid-soluble hormones can cross the cell membrane and bind to receptor proteins inside the target cell, activating specific genes. Surface receptors are the typical route for water-soluble hormones.

5. A water-soluble hormone reaches a target cell but cannot cross its membrane. What happens next?

A. It enters a duct and is transported into the cell by glandular secretion

B. It binds to a surface receptor that initiates intracellular reactions

C. It dissolves through the lipid bilayer and binds to a cytoplasmic receptor

D. It diffuses into the nucleus and directly activates a specific gene

Answer: (B)

Explanation

Water-soluble hormones cannot cross the cell membrane, so they bind to receptors on the cell surface and trigger an intracellular reaction cascade. Direct entry into the cell and intracellular receptor binding characterize lipid-soluble hormone action.

6. What is the defining effect of negative feedback in a homeostatic system?

A. The system’s final response causes an unrelated organ to begin hormone secretion

B. The system’s output suppresses or inhibits activity within the same system

C. The system’s output intensifies the process that produced the original signal

D. The system’s receptors permanently stop detecting changes in the internal environment

Answer: (B)

Explanation

Negative feedback reduces activity within the system after its output increases, helping maintain homeostasis. Intensifying the original process describes positive reinforcement rather than negative feedback.

7. What sequence occurs when blood plasma becomes too concentrated?

A. The pituitary reduces ADH, the kidneys excrete water, and plasma concentration rises further

B. The kidneys release ADH, the hypothalamus excretes water, and concentration remains elevated

C. The hypothalamus blocks pituitary activity, the kidneys retain less water, and dilution stops

D. The hypothalamus signals ADH release, the kidneys retain water, and ADH release then decreases

Answer: (D)

Explanation

High plasma concentration causes hypothalamic signaling that leads to posterior-pituitary ADH release; ADH promotes kidney water retention and dilution. Once concentration returns toward normal, signaling to release ADH decreases.

8. Which sequence correctly describes a tropic hormone pathway?

A. The target endocrine gland releases a releasing hormone, the pituitary activates the hypothalamus, and the final hormone bypasses feedback

B. The hypothalamus releases a releasing hormone, the anterior pituitary releases a tropic hormone, and the final hormone inhibits both earlier signals

C. The anterior pituitary releases a releasing hormone, the hypothalamus releases a tropic hormone, and the final hormone increases both earlier signals

D. The hypothalamus releases a final hormone, an endocrine gland releases a tropic hormone, and the pituitary suppresses the hypothalamus

Answer: (B)

Explanation

In a tropic pathway, the hypothalamus first signals the anterior pituitary, which releases a tropic hormone that stimulates another endocrine gland. The final hormone feeds back to inhibit further release of the hypothalamic and pituitary hormones.

9. Which statement correctly distinguishes the two lobes of the pituitary gland?

A. The anterior lobe stores and releases hormones, whereas the posterior lobe produces and releases its hormones.

B. The posterior lobe stores and releases hormones, whereas the anterior lobe produces and releases its hormones.

C. Both lobes store hormones made by the adrenal glands before releasing them into circulation.

D. Both lobes produce and release hormones after receiving direct signals from the thyroid gland.

Answer: (B)

Explanation

The posterior pituitary stores and releases hormones, while the anterior pituitary produces and releases its listed hormones. The reverse arrangement is a common confusion and does not describe pituitary function.

10. Which effect is associated with human growth hormone in a growing child?

A. It triggers calcium uptake into bones while preventing protein synthesis in body tissues.

B. It stimulates long-bone growth, protein synthesis, and the release of stored fats.

C. It reduces metabolism while directing thyroid hormones into developing skeletal muscle.

D. It suppresses cellular division, connective-tissue growth, and the use of stored energy.

Answer: (B)

Explanation

Human growth hormone supports growth and development by stimulating long-bone and connective-tissue growth, protein synthesis, cell division, and fat release. Calcium uptake into bones is associated with calcitonin rather than human growth hormone.

11. What happens when rising thyroxine levels are detected in the negative-feedback system controlling thyroid activity?

A. The thyroid receives stronger stimulation to release additional thyroxine.

B. The adrenal medulla releases catecholamines to maintain thyroid stimulation.

C. The parathyroid glands release PTH to increase thyroid hormone production.

D. Hypothalamic and anterior-pituitary release of TSH is suppressed.

Answer: (D)

Explanation

Rising thyroxine suppresses TSH release from both the hypothalamus and anterior pituitary, limiting further thyroid stimulation. Increased TSH would occur when thyroxine feedback is reduced, not when thyroxine levels rise.

12. Why can inadequate iodine lead to enlargement of the thyroid gland?

A. Low iodine blocks ACTH release, causing adrenal hormones to accumulate inside the thyroid.

B. Low iodine prevents thyroxine production, causing persistent TSH stimulation and thyroid growth.

C. Low iodine activates calcitonin release, which enlarges the thyroid while lowering blood calcium.

D. Low iodine directly increases thyroxine production, causing the thyroid to expand from metabolic activity.

Answer: (B)

Explanation

Iodine is required for thyroid hormone production, so inadequate iodine reduces thyroxine and can produce relentless TSH stimulation that enlarges the thyroid into a goitre. The other choices assign iodine-related effects to unrelated hormones or reverse the effect on thyroxine.

13. A person has an abnormally high blood calcium concentration. Which hormonal response helps lower it?

A. Cortisol promotes amino-acid conversion into glucose.

B. Calcitonin stimulates calcium uptake into bones.

C. PTH stimulates calcium release from bones.

D. TSH increases thyroxine secretion from the thyroid.

Answer: (B)

Explanation

When blood calcium is too high, calcitonin promotes calcium uptake into bones, lowering the concentration in the blood. PTH has the contrasting effect of raising blood calcium when calcium levels fall.

14. What is the main effect of parathyroid hormone when blood calcium concentration falls?

A. It lowers blood calcium by preventing bone breakdown and reducing kidney calcium reabsorption.

B. It lowers blood calcium by moving calcium into bone and reducing intestinal calcium absorption.

C. It raises blood calcium through bone breakdown, kidney reabsorption, vitamin D activation, and intestinal absorption.

D. It raises blood calcium by suppressing vitamin D activation and increasing urinary calcium loss.

Answer: (C)

Explanation

PTH is released when blood calcium falls and raises it through several coordinated actions, including bone breakdown, kidney calcium reabsorption, vitamin D activation, and increased intestinal absorption. The alternatives describe calcium-lowering effects or reverse the roles of PTH and calcitonin.

15. Which anatomical description of the adrenal glands is correct?

A. They sit on top of the kidneys, with an inner medulla and an outer cortex.

B. They surround the pituitary, with a central cortex and a peripheral medulla.

C. They attach to the thyroid, with an inner cortex and an outer medulla.

D. They lie beneath the kidneys, with an outer medulla and an inner cortex.

Answer: (A)

Explanation

Each adrenal gland lies on top of a kidney and contains an inner adrenal medulla surrounded by an outer adrenal cortex. Reversing the medulla and cortex is the key anatomical confusion addressed by this distinction.

16. How are adrenal-medulla hormones activated during a rapid fight-or-flight response?

A. The anterior pituitary releases TSH, which instructs the medulla to release thyroid hormones.

B. Hypothalamic hormones indirectly stimulate the cortex to release epinephrine and norepinephrine.

C. Low blood calcium directly signals the medulla to release cortisol and aldosterone.

D. Sympathetic neurons directly signal the medulla to release epinephrine and norepinephrine.

Answer: (D)

Explanation

Sympathetic neurons directly activate the adrenal medulla, producing rapid release of epinephrine and norepinephrine during fight-or-flight responses. Cortisol release, in contrast, requires a hypothalamus–pituitary hormone pathway and comes from the adrenal cortex.

17. How does cortisol raise blood glucose during a prolonged stress response?

A. It increases blood glucose by causing the adrenal medulla to release thyroid-stimulating hormone.

B. It promotes muscle-protein and fat breakdown, allowing the liver to use amino acids to make glucose.

C. It drives calcium into bone and uses thyroid hormones to convert glucose into stored fat.

D. It stimulates skeletal muscle to store glucose while preventing the liver from making new glucose.

Answer: (B)

Explanation

Cortisol raises blood glucose by promoting the breakdown of muscle protein and fat, while the liver uses resulting amino acids to make glucose. The other choices describe calcium regulation, glucose storage, or hormones that are not produced by the adrenal cortex.

18. Which pancreatic hormone increases glucose uptake by target cells and promotes glycogen formation in the liver?

A. Cortisol released by the adrenal cortex

B. Insulin released by pancreatic beta cells

C. Glucagon released by pancreatic alpha cells

D. Antidiuretic hormone released by the posterior pituitary

Answer: (B)

Explanation

Insulin from beta cells makes target cells more permeable to glucose and promotes its storage as glycogen in the liver. Glucagon has the opposing effect of raising blood glucose by promoting glucose release from the liver.

19. During prolonged fasting, which response helps maintain the blood glucose supply?

A. Alpha cells release insulin, causing muscle cells to increase glucose uptake

B. Alpha cells release glucagon, causing the liver to convert glycogen into glucose

C. Beta cells release glucagon, causing the kidneys to reabsorb more water

D. Beta cells release insulin, causing the liver to store more glucose as glycogen

Answer: (B)

Explanation

During fasting, pancreatic alpha cells release glucagon, which stimulates the liver to break down glycogen and release glucose into the blood. Insulin is associated with glucose uptake and storage rather than raising blood glucose during fasting.

20. Which condition is characterized by persistently high blood glucose after meals because the body lacks insulin or responds poorly to it?

A. Diabetes insipidus

B. Diabetes mellitus

C. Excess antidiuretic hormone activity

D. Pancreatic glycogen storage

Answer: (B)

Explanation

Diabetes mellitus involves inadequate insulin production or reduced cellular responsiveness to insulin, resulting in elevated blood glucose after meals. Diabetes insipidus instead concerns ADH, water balance, and urine production.

21. A child develops diabetes after immune destruction of pancreatic beta cells and requires regular insulin injections; which type of diabetes is most consistent with this pattern?

A. Diabetes insipidus

B. Type 2 diabetes

C. Post-meal hyperglycemia from excess glucagon

D. Type 1 diabetes

Answer: (D)

Explanation

Type 1 diabetes results from immune destruction of pancreatic beta cells and therefore requires insulin replacement. Type 2 diabetes develops through reduced insulin-receptor responsiveness and may be managed with diet and exercise.

22. When blood plasma becomes highly concentrated, how does antidiuretic hormone help restore water balance?

A. It is released from the pancreas and causes the liver to convert glycogen into glucose

B. It is released from the anterior pituitary and causes kidney nephrons to excrete more water

C. It is released from the hypothalamus directly into urine and reduces water reabsorption

D. It is released from the posterior pituitary and causes kidney nephrons to reabsorb more water

Answer: (D)

Explanation

ADH is produced in the hypothalamus, stored in the posterior pituitary, and released when plasma concentration is high; it increases water reabsorption by kidney nephrons. The hormone does not originate in the pancreas or promote increased water loss.

23. Which finding most strongly indicates diabetes insipidus rather than diabetes mellitus?

A. High blood glucose after meals caused by absent or ineffective insulin

B. Reduced insulin-receptor responsiveness that improves with diet and exercise

C. Large urine volumes caused by insufficient ADH, with loss of ions from the blood

D. Immune destruction of beta cells followed by a need for insulin injections

Answer: (C)

Explanation

Diabetes insipidus results from insufficient ADH and causes abundant urine production with loss of ions from the blood; ADH medication can treat it. High post-meal blood glucose and beta-cell destruction are features of diabetes mellitus, not diabetes insipidus.