Nokea
The reason for naming the closed circulatory systems
- A. Carries blood in opens vessels
- B. Moves blood through the veins and arteries
- C. Blood stays confined to vessels
- D. Returns blood to the heart
Correct Answer: C
Rationale: The correct answer is C because a closed circulatory system means that blood stays confined to vessels, providing efficient transport and preventing blood loss. Option A is incorrect because a closed system does not have open vessels. Option B is incorrect because veins and arteries are part of both closed and open circulatory systems. Option D is incorrect because returning blood to the heart is a function of both closed and open circulatory systems.
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With respect to vaccination against a particular infectious disease 'herd immunity' refers to:
- A. The total number of people who are immunized in a given population
- B. The protection offered to non-immunized people when high rates of immunization prevent the pathogen from spreading
- C. The percentage of people who generate a protective response to the vaccine
- D. The tendency of people to choose to be vaccinated if close contacts (friends and family) have been vaccinated
Correct Answer: B
Rationale: The correct answer is B. Herd immunity refers to the protection offered to non-immunized individuals when a high percentage of the population is immunized, preventing the pathogen from spreading easily. This is because when a large portion of the population is immune to a disease, it creates a barrier that reduces the overall transmission of the pathogen, thus protecting those who are not vaccinated or cannot be vaccinated.
Choice A is incorrect because herd immunity is not solely about the total number of immunized individuals, but rather about the impact on the entire population. Choice C is incorrect as it refers to the efficacy of the vaccine in generating a protective response, not the concept of herd immunity. Choice D is incorrect as it relates to social influence rather than the collective protection provided by high rates of immunization.
Match the following terms (1-6) with their respective meanings (A-F).
- A. 1A-2B-3E-4F-5C-6D
- B. 1D-2C-3A-4B-5E-6F
- C. 1D-2C-3B-4E-5A-6F
- D. 1C-2A-3B-4E-5F-6D
Correct Answer: C
Rationale: The correct match for the terms is:
1 - D
2 - C
3 - B
4 - E
5 - A
6 - F
Rationale:
1. Term 1 corresponds to definition D, as per choice C.
2. Term 2 matches with definition C, as per choice C.
3. Term 3 aligns with definition B, as per choice C.
4. Term 4 correlates with definition E, as per choice C.
5. Term 5 matches with definition A, as per choice C.
6. Term 6 corresponds to definition F, as per choice C.
Summary:
- Choice A has incorrect matches for terms 1, 2, 3, 5, and 6.
- Choice B has incorrect matches for terms 1, 2, 3, and 4.
- Choice D has incorrect matches for terms 1, 2, 4, and 6.
Therefore, the correct answer
All of the following are true EXCEPT
- A. An epitope is a small portion of a macromolecule
- B. the variable region domains contain the antigen recognition site
- C. an antigenic determinant is a paratope
- D. The class of an immunoglobulin is determined by its heavy chain
Correct Answer: C
Rationale: The correct answer is C because an antigenic determinant is not a paratope, but an epitope. Epitope is a small portion of a macromolecule that is recognized by antibodies. Variable region domains of antibodies contain the antigen recognition site. The class of an immunoglobulin is indeed determined by its heavy chain. Therefore, C is the only statement that is not true.
Which of the following is a characteristic of CTL?
- A. They kill target cells through recognition of peptide-MHC class I complexes
- B. They die in the process of killing a target cell
- C. They can kill target cells by activating complement
- D. They carry out their effector function in secondary lymphoid tissues
Correct Answer: A
Rationale: The correct answer is A because cytotoxic T lymphocytes (CTLs) kill target cells by recognizing specific peptide antigens presented on major histocompatibility complex (MHC) class I molecules. This recognition triggers the CTLs to release cytotoxic molecules that induce apoptosis in the target cells. Choice B is incorrect because CTLs do not die in the process of killing target cells; they survive to continue their immune response. Choice C is incorrect as CTLs do not kill target cells by activating complement, but rather through direct cell-cell contact. Choice D is incorrect because CTLs carry out their effector function in peripheral tissues where they encounter target cells, not specifically in secondary lymphoid tissues.
What is the primary function of cytokines in the immune system?
- A. To act as a physical barrier to pathogens
- B. To orchestrate and drive immune responses
- C. To destroy red blood cells
- D. To generate antibodies
Correct Answer: B
Rationale: The correct answer is B: To orchestrate and drive immune responses. Cytokines are signaling molecules that coordinate various aspects of the immune response, such as inflammation, cell proliferation, and differentiation. They regulate communication between immune cells to mount an effective defense against pathogens.
A: To act as a physical barrier to pathogens - Incorrect. Physical barriers include skin and mucous membranes, not cytokines.
C: To destroy red blood cells - Incorrect. Cytokines are not involved in destroying red blood cells.
D: To generate antibodies - Incorrect. While cytokines can influence antibody production, their primary role is not in generating antibodies.