Homeostasis and Kidney Regulation Practice Quiz (22 questions)

1. What does homeostasis enable the body to do despite changes in the external environment?

A. Maintain relative stability in the components of its internal environment

B. Maintain stable conditions only when the external environment is constant

C. Keep the external environment stable by changing internal conditions

D. Prevent all changes in the body's internal environment

Answer: (A)

Explanation

Homeostasis is the body's ability to keep its internal environment relatively stable despite ongoing external changes. Preventing every internal change is not required; the stability is relative.

2. What is the term for regulating the composition of internal fluids such as blood, lymph, and interstitial fluid?

A. Osmoregulation

B. Neurotransmission

C. Thermoregulation

D. Excretion

Answer: (A)

Explanation

Osmoregulation is the regulation that maintains the composition of an organism's internal environment, including these extracellular fluids. Thermoregulation concerns temperature rather than the composition of those fluids.

3. A cell is placed in a solution with a higher solute concentration than its own. What is the likely effect on the cell?

A. Water leaves the cell, causing it to dehydrate

B. Solutes leave the cell, causing it to expand

C. Water enters the cell, causing it to swell

D. Water moves equally in both directions, preserving its volume

Answer: (A)

Explanation

A hypertonic solution has a higher solute concentration than the cell, so water leaves the cell and it dehydrates. A hypotonic solution, rather than a hypertonic one, causes water to enter and the cell to swell.

4. Which set lists the components of a homeostatic control system?

A. A controlled variable, integration centre, gland, feedback loop, and stimulus

B. A set point, receptor, sensory neuron, motor neuron, and external environment

C. A stimulus, controlled variable, receptor, integration centre, and effector with its response

D. A stimulus, hormone, blood vessel, target organ, and behavioral response

Answer: (C)

Explanation

The system includes a stimulus, a controlled factor or variable, a receptor, a control or integration centre, and an effector with its response. A hormone or sensory neuron may participate in regulation, but neither replaces this full set of components.

5. What is the role of a receptor in a homeostatic control system?

A. Detect a parameter or its change and translate it into a nerve or hormonal message

B. Create a stimulus that changes the regulated parameter

C. Compare a detected value with the set point and choose the strength of compensation

D. Act on the regulated parameter to return it toward its set point

Answer: (A)

Explanation

Receptors detect a parameter or a change in it and translate that information into a nerve or hormonal message. Comparing the information with the set point is the integration centre's role.

6. When a controlled variable deviates from its set point, how does the control centre contribute to homeostatic correction?

A. It detects the deviation and directly changes the regulated parameter without an effector

B. It compares the information with the set point and determines effector activity and compensation intensity

C. It converts the deviation into a stimulus and sets a new value for the variable

D. It acts on the regulated parameter while the receptor determines compensation intensity

Answer: (B)

Explanation

The control centre compares received information with the set point and uses the deviation to determine effector activity and compensation intensity. The effector, rather than the control centre, acts on the regulated parameter.

7. Which description best characterizes nervous-system regulation compared with slower hormonal effects?

A. It relies on interstitial fluid diffusion and has delays measured in days

B. It acts through target-cell DNA and generally takes several hours to produce a response

C. It uses neurons and synaptic spaces to communicate rapidly, with impulse delays on the order of a second or less

D. It uses hormones carried in blood and interstitial fluid, with effects that commonly last months

Answer: (C)

Explanation

Nervous signaling uses neurons and synaptic spaces and is the fastest, shortest-acting regulatory system, with delays around a second or less. Effects of steroid and thyroid hormones can take hours to months, rather than occurring on that rapid timescale.

8. How does the endocrine system carry its messages to target tissues?

A. Hormones move directly from gland cells into target-cell DNA

B. Receptors carry nerve messages through the lymph and into target tissues

C. Hormones travel through the blood and then the interstitial fluid

D. Neurons carry electrical impulses across synaptic spaces

Answer: (C)

Explanation

Endocrine messages are hormones transported through the blood and then the interstitial fluid. Neurons and synaptic spaces are the communication route associated with nervous-system signaling.

9. Which comparison correctly distinguishes peptide hormones from steroid and thyroid hormones?

A. Peptide hormones act at the cell membrane, while steroid and thyroid hormones act at target-cell DNA

B. Peptide hormones act at target-cell DNA, while steroid and thyroid hormones act at the cell membrane

C. Both hormone groups enter cells and act at DNA, but peptide effects develop more slowly

D. Both hormone groups act at the cell membrane, but steroid and thyroid effects develop more quickly

Answer: (A)

Explanation

Peptide hormones act at the cell membrane without entering the cell, whereas steroid and thyroid hormones act at the DNA of target cells. The reverse assignment of these action sites is a common confusion.

10. When a regulated variable deviates from its current level, what does negative feedback do?

A. It prevents the variable from changing from its current level.

B. It starts a response before the variable has changed.

C. It reduces the deviation and moves the variable toward a dynamic equilibrium.

D. It amplifies the deviation until the initial disturbance disappears.

Answer: (C)

Explanation

Negative feedback counteracts a deviation, returning the changing variable toward a new dynamic equilibrium rather than maintaining perfect constancy. Amplification of the initial disturbance describes positive feedback.

11. In a positive feedback loop, what happens after an initial perturbation triggers a response?

A. The response amplifies the perturbation, potentially creating a snowball effect until the initial disturbance disappears.

B. The response reduces the perturbation and stabilizes the variable near its previous level.

C. The response holds the variable at a constant level while the disturbance continues.

D. The response begins before the perturbation and prevents the variable from changing.

Answer: (A)

Explanation

Positive feedback reinforces the initial perturbation and can produce a snowball effect until the disturbance disappears. A response that reduces the deviation is characteristic of negative feedback.

12. Which combination describes important functions of the kidneys?

A. Producing digestive enzymes and regulating oxygen and carbon dioxide concentrations in blood.

B. Producing blood cells and regulating body temperature, pH, and blood pressure.

C. Filtering lymph to remove pathogens and regulating glucose and protein concentrations in blood.

D. Filtering blood to remove metabolic waste and regulating water balance, pH, and blood ion concentrations.

Answer: (D)

Explanation

The kidneys filter blood to eliminate metabolic waste and help regulate water balance, pH, and concentrations of several ions. Filtering lymph and removing pathogens is not the kidney role described here.

13. Which statement correctly identifies the two chief hormones involved in regulating urinary excretion and where they are produced or released?

A. Aldosterone is synthesized by the adrenal cortex, while ADH is produced by the hypothalamus and released into blood by the pituitary.

B. Aldosterone is synthesized by the pituitary, while ADH is produced by the adrenal cortex and released into blood by the hypothalamus.

C. Aldosterone is produced by the kidneys, while ADH is synthesized by the liver and released into blood by the adrenal cortex.

D. Aldosterone is synthesized by the hypothalamus, while ADH is produced by the pituitary and released into blood by the kidneys.

Answer: (A)

Explanation

Aldosterone is synthesized by the adrenal cortex, and ADH is produced by the hypothalamus and released into the bloodstream by the pituitary. The pituitary does not synthesize aldosterone, as the second statement suggests.

14. Which statement about sodium in body fluids is correct?

A. It is the most abundant ion in extracellular fluid and comes from dietary sodium chloride.

B. It is the most abundant ion in plasma but is scarce in interstitial fluid and lymph.

C. It is the most abundant ion in intracellular fluid and comes mainly from dietary potassium salts.

D. It is a minor ion in extracellular fluid and comes mainly from the breakdown of proteins.

Answer: (A)

Explanation

Sodium is the most abundant ion in extracellular fluid, including interstitial fluid, lymph, and plasma, and it comes from dietary sodium chloride. The claim that it is most abundant in intracellular fluid describes a different distribution.

15. When sodium is reabsorbed from the kidney tubule into the blood, what tends to happen to water?

A. Water follows potassium into the blood instead of following sodium.

B. Water remains in the tubule because sodium reabsorption blocks osmosis.

C. Water moves into the tubule as sodium enters the blood.

D. Water follows the sodium by osmosis, moving toward the blood.

Answer: (D)

Explanation

As the kidney reabsorbs sodium from the tubule into the blood, water tends to follow by osmosis. The claim that sodium reabsorption blocks water movement reverses this relationship.

16. When the body needs to conserve water, how does ADH affect the distal tubule and collecting duct?

A. It increases sodium loss so water is retained in the filtrate.

B. It decreases their permeability so less water is extracted from the filtrate.

C. It decreases water permeability, while alcohol and caffeine enhance water reabsorption.

D. It increases their permeability so more water is extracted from the filtrate.

Answer: (D)

Explanation

ADH increases the permeability of the distal tubule and collecting duct, allowing more water to be reabsorbed from the filtrate. Alcohol and caffeine inhibit ADH and increase urinary water excretion, contrary to the final option.

17. If blood volume and pressure fall too low to support glomerular filtration, which sequence helps restore them?

A. The kidneys release renin, which triggers aldosterone secretion; aldosterone increases sodium reabsorption, and chloride and water follow.

B. The kidneys release ADH, which triggers aldosterone secretion; aldosterone increases potassium reabsorption, and chloride follows.

C. The kidneys release aldosterone, which triggers renin secretion; renin increases water reabsorption, and sodium follows.

D. The kidneys release renin, which suppresses aldosterone; reduced sodium reabsorption then raises blood volume.

Answer: (A)

Explanation

Low blood volume and pressure prompt renal renin release, which triggers aldosterone secretion; increased sodium reabsorption then draws chloride and water along, helping raise blood volume and pressure. The second sequence reverses the relationship between renin and aldosterone.

18. Which reversible reaction system helps buffer changes in blood pH?

A. $\mathrm{Na^+ + Cl^- \leftrightarrow NaCl \leftrightarrow Na + Cl_2}$

B. $\mathrm{Ca^{2+} + PO_4^{3-} \leftrightarrow Ca_3(PO_4)_2 \leftrightarrow Ca + P}$

C. $\mathrm{H^+ + HCO_3^- \leftrightarrow H_2CO_3 \leftrightarrow H_2O + CO_2}$

D. $\mathrm{H^+ + O_2 \leftrightarrow H_2O_2 \leftrightarrow H_2O + O_2}$

Answer: (C)

Explanation

The bicarbonate buffer system reversibly links hydrogen ions, bicarbonate, carbonic acid, water, and carbon dioxide to regulate pH. The oxygen-based reaction is not the buffer system described here.

19. Which comparison correctly describes the pH of healthy blood and urine?

A. Blood ranges from 4.5 to 8; urine is about 7.4 and averages about 6.6.

B. Blood is about 7.4; urine ranges from 6.6 to 8 and averages about 4.5.

C. Blood is about 7.4; urine ranges from 4.5 to 8 and averages about 6.6.

D. Blood averages about 6.6; urine is about 7.4 and ranges from 4.5 to 8.

Answer: (C)

Explanation

Healthy blood pH is about 7.4, while urine varies between 4.5 and 8 and averages approximately 6.6. The second comparison reverses the blood and urine values.

20. When blood becomes acidic, how does increased breathing help restore acid–base balance?

A. It shifts the buffer reaction toward carbon dioxide production, which is removed in exhaled air.

B. It shifts the buffer reaction toward bicarbonate production, which is removed in exhaled air.

C. It reduces carbon dioxide production, causing more carbon dioxide to leave through the kidneys.

D. It increases calcium absorption, which directly removes acid from the blood.

Answer: (A)

Explanation

Increased ventilation shifts the buffer reaction toward carbon dioxide production, and exhalation removes that carbon dioxide. Bicarbonate is not the substance eliminated in exhaled air.

21. What is the role of kidney-secreted erythropoietin (EPO)?

A. It activates vitamin D production in the skin.

B. It stimulates red blood cell production in the bone marrow.

C. It promotes calcium absorption in the digestive tract.

D. It stimulates white blood cell production in the bone marrow.

Answer: (B)

Explanation

Kidney-secreted EPO stimulates red blood cell production in the bone marrow. White blood cell production is a different process and is not the role identified for EPO.

22. Which vitamin-related function is attributed to the kidneys?

A. They release calcitriol to stimulate vitamin D production in the skin.

B. They produce parathyroid hormone to increase calcium absorption.

C. They secrete vitamin D to stimulate red blood cell production.

D. They activate the production of vitamin D in the skin.

Answer: (D)

Explanation

The stated kidney function is activating the production of vitamin D in the skin. Parathyroid hormone is released by the parathyroid glands, not produced by the kidneys.