QCM : Fundamentals of Human Blood and Homeostasis — 18 questions

Questions et réponses du QCM

1. What best describes the internal environment of the body?

The fluid contained only inside red blood cells
The total amount of water inside the digestive tract
The hormonal secretions released by endocrine glands
The set of extracellular fluids bathing the cells

The set of extracellular fluids bathing the cells

Explication

The internal environment, or milieu intérieur, refers to the extracellular liquids surrounding and bathing the cells. The other choices describe cellular, digestive, or hormonal contents rather than the body's internal extracellular environment.

2. Which statement best describes negative feedback in homeostatic control?

It counteracts a change to restore balance
It occurs only when blood glucose rises
It depends exclusively on voluntary behavior
It amplifies the initial change until a final event occurs

It counteracts a change to restore balance

Explication

Negative feedback reverses or counteracts a disturbance to bring conditions back toward normal. Amplifying the change describes positive feedback, not negative feedback.

3. What is a key function of blood plasma?

It contains fibrinogen only after blood has clotted
It stores oxygen exclusively inside white blood cells
It is made primarily of platelets and leukocytes
It transports nutrients, gases, hormones, enzymes, and wastes

It transports nutrients, gases, hormones, enzymes, and wastes

Explication

Plasma is the liquid phase of blood and serves as a transport medium for many substances. Fibrinogen is present in plasma, not serum, and formed elements are the cells and platelets.

4. What distinguishes serum from plasma?

Serum is the cellular portion of blood
Serum contains more fibrinogen than plasma
Serum is identical to plasma except for albumin
Serum is obtained after coagulation and lacks fibrinogen

Serum is obtained after coagulation and lacks fibrinogen

Explication

Serum is the fluid remaining after coagulation, so it lacks fibrinogen and other clotting factors consumed in clot formation. Plasma, in contrast, still contains coagulation factors.

5. Where does hematopoiesis primarily occur in adults?

In the thymus
In the bone marrow
In the lymph nodes
In the spleen

In the bone marrow

Explication

Hematopoiesis is the continuous production of blood cells and occurs in the bone marrow. The thymus is for T-cell education, and spleen and lymph nodes are secondary lymphoid organs.

6. What is the main role of platelets in hemostasis?

They form the platelet plug during primary hemostasis
They dissolve fibrin after clot formation
They produce antibodies against exposed antigens
They carry oxygen to tissues

They form the platelet plug during primary hemostasis

Explication

Platelets are essential for primary hemostasis because they aggregate to form the platelet plug. They do not transport oxygen or produce antibodies.

7. What determines ABO and Rh blood groups?

The amount of plasma proteins in the blood
The concentration of glucose in the blood
The number of leukocytes circulating in plasma
The antigens present on the surface of red blood cells

The antigens present on the surface of red blood cells

Explication

ABO and Rh blood groups are defined by antigens on red blood cell membranes. They are not determined by plasma protein levels or glucose concentration.

8. Which disorder is characterized by uncontrolled proliferation of white blood cells?

Leukemia
Anemia
Thrombosis
Hemophilia

Leukemia

Explication

Leukemia is defined by uncontrolled proliferation of white blood cells. Anemia involves reduced oxygen transport, while hemophilia and thrombosis are clotting-related disorders.

9. How much of total body water is normally located in the extracellular fluid compartment?

About one-third
About three-quarters
About one-tenth
About two-thirds

About one-third

Explication

Extracellular fluid makes up about one-third of total body water, while intracellular fluid accounts for about two-thirds. This split is important for predicting fluid shifts.

10. What happens when plasma osmolality rises?

Thirst is triggered and ADH is secreted
The kidneys stop filtering sodium
Water moves into cells and urine becomes more dilute
Thirst is inhibited and ADH secretion falls

Thirst is triggered and ADH is secreted

Explication

When osmolality rises, the hypothalamus triggers thirst and ADH release to reduce urinary water loss. This helps restore osmotic balance by conserving water.

11. What is the main effect of isotonic saline on body fluid compartments?

It expands extracellular volume without causing a net water shift into cells
It pulls water out of cells and increases intracellular osmolality
It causes rapid loss of both intracellular and extracellular water
It drives water into cells and increases intracellular volume

It expands extracellular volume without causing a net water shift into cells

Explication

Isotonic saline matches extracellular osmotic conditions, so it mainly increases extracellular volume. It does not create a gradient that would shift water significantly into or out of cells.

12. Which mechanism directly maintains the sodium and potassium gradients across the cell membrane?

Diffusion through the lipid bilayer keeps sodium and potassium balanced
The Na+,K+-ATPase pump uses ATP to export sodium and import potassium
Fibrinogen forms channels that exchange sodium and potassium
Aquaporins move sodium and potassium to equalize osmotic pressure

The Na+,K+-ATPase pump uses ATP to export sodium and import potassium

Explication

The Na+,K+-ATPase pump expels 3 Na⁺ and brings in 2 K⁺ using ATP, preserving the gradients. Aquaporins transport water, not ions.

13. Which statement best describes the role of the immune system in organization and control?

It acts only by destroying pathogens once they enter the body
It functions independently of soluble mediators such as cytokines
It is limited to circulating white blood cells and has no tissue component
It combines communication, effector action, and regulation to maintain immune balance

It combines communication, effector action, and regulation to maintain immune balance

Explication

The immune system is organized around communication, protective effector capacity, and regulation. Cytokines and chemokines are important soluble mediators for this coordination.

14. What can happen when immune homeostasis is deregulated?

The immune system becomes unable to circulate through the body
Immune deficits, autoimmune disease, or hypersensitivity can develop
All immune communication stops permanently
Only increased red blood cell production occurs

Immune deficits, autoimmune disease, or hypersensitivity can develop

Explication

The source states that loss of immune balance can lead to immune deficits, autoimmune diseases, or hypersensitivities. The other options do not match the described consequences.

15. Which feature best characterizes innate immunity?

It relies exclusively on antibody-producing plasma cells
It provides rapid, nonspecific defense as a first line of protection
It develops slowly and creates long-term memory after exposure
It requires prior antigen exposure to function effectively

It provides rapid, nonspecific defense as a first line of protection

Explication

Innate immunity is the rapid, nonspecific first defense line. Memory and delayed specificity are features of adaptive immunity, not innate immunity.

16. Which cell type is described as the most powerful antigen-presenting cell for activating naive T lymphocytes?

Erythrocytes
Basophils
Neutrophils
Dendritic cells

Dendritic cells

Explication

Dendritic cells are the most powerful antigen-presenting cells for activating naive T cells. Neutrophils are mainly phagocytes in acute inflammation.

17. Which pairing of organ and function is correct?

Bone marrow supports hematopoiesis and B-cell maturation
Thymus filters circulating blood for antigens
Lymph nodes are the primary site of red blood cell production
Spleen is the main site of T-cell education and selection

Bone marrow supports hematopoiesis and B-cell maturation

Explication

Bone marrow is a primary lymphoid organ where hematopoiesis and B-cell maturation occur. The thymus educates T cells, while spleen and lymph nodes are secondary organs.

18. What is the main role of mucosa-associated lymphoid tissue, or MALT?

It protects mucosal surfaces such as the respiratory and digestive tracts
It produces only circulating antibodies in the bloodstream
It filters blood to remove aged red blood cells
It is the site where all T lymphocytes are selected

It protects mucosal surfaces such as the respiratory and digestive tracts

Explication

MALT guards mucosal surfaces and includes structures such as tonsils and Peyer’s patches. Blood filtering is a function of the spleen, not MALT.

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Internal environment — definition?

Extracellular liquids bathing cells.

Claude Bernard — role?

Introduced concept of internal environment.

Homeostasis — purpose?

Maintain stable internal environment.

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