Anatomy
1 questionsT cells in lymph node are present in:
NEET-PG 2013 - Anatomy NEET-PG Practice Questions and MCQs
Question 591: T cells in lymph node are present in:
- A. Paracortical area (Correct Answer)
- B. Mantle layer
- C. Medullary cords
- D. Cortical follicles
Explanation: ***Paracortical area*** - The **paracortical area** contains a high concentration of **T cells**, particularly activated T cells in response to antigenic stimulation [1]. - It plays a crucial role in **immune responses**, bridging the cortex and medulla of the lymph node [1]. *Mantle layer* - The **mantle layer** surrounds the follicles and primarily consists of **B cells**, not T cells. - It is involved in the initial immune response but does not contain a significant number of T lymphocytes. *Medullary cords* - **Medullary cords** mainly contain **plasma cells** and macrophages, with very few T cells present. - Their primary function is the secretion of antibodies rather than T cell activation or response. *Cortical follicles* - **Cortical follicles** are primarily sites for **B cell activation and proliferation**. - While they may have some T cells at their periphery, the majority of T cells are located in the paracortical area.
Biochemistry
1 questionsWhich immunoglobulin is known to be heat-labile?
NEET-PG 2013 - Biochemistry NEET-PG Practice Questions and MCQs
Question 591: Which immunoglobulin is known to be heat-labile?
- A. IgA
- B. IgG
- C. IgM (Correct Answer)
- D. IgE
Explanation: ***IgM*** - **IgM** is known for its **heat lability** and is readily denatured at 56°C within a few minutes. - This characteristic is due to its **pentameric structure** held together by disulfide bonds and J chains, which are sensitive to thermal denaturation. - Heat lability of IgM is clinically important in complement fixation tests and other laboratory assays where heat inactivation is performed. - IgM is the first antibody produced in primary immune response and its heat sensitivity distinguishes it from other immunoglobulins. *IgA* - **IgA** exists in monomeric (serum) and dimeric (secretory) forms and shows moderate stability to heat. - Secretory IgA is relatively stable as it needs to function in harsh mucosal environments, though not as heat-resistant as IgG. - Does not exhibit the pronounced heat lability characteristic of IgM. *IgG* - **IgG** is the most stable immunoglobulin and is highly resistant to heat denaturation. - Can withstand temperatures up to 60-70°C without significant loss of activity. - Its monomeric structure with strong intramolecular bonds provides exceptional thermal stability. - Most abundant antibody in serum and has the longest half-life. *IgE* - **IgE** is actually quite stable to heat and can withstand 56°C for extended periods. - While it has a short half-life in serum (2-3 days), this is due to receptor binding rather than heat instability. - Important in type I hypersensitivity reactions and parasitic infections. - Does not show the characteristic heat lability that defines IgM.
Community Medicine
1 questionsMost important component of level of living is
NEET-PG 2013 - Community Medicine NEET-PG Practice Questions and MCQs
Question 591: Most important component of level of living is
- A. Education
- B. Housing
- C. Health
- D. Occupation (Correct Answer)
Explanation: ***Occupation*** - **Occupation** is the most important component of the level of living as it is the primary determinant of **income**, which forms the economic foundation of the level of living. - In Community Medicine, "level of living" is an **objective economic indicator** primarily measured by income and consumption patterns, distinguishing it from the broader concept of "quality of life." - A stable and remunerative occupation ensures regular income, which directly enables individuals to afford basic necessities (food, clothing, shelter) and access other essential resources like healthcare and education. - Occupation also confers social status and determines the standard of living that an individual or family can maintain. *Education* - While **education** is crucial for human development and enhances future opportunities, it serves as a means to achieve better employment rather than being a direct component of the level of living itself. - Education's impact on living standards is realized primarily through its influence on occupational opportunities and earning potential. *Housing* - **Housing** is an important indicator of living standards and reflects the level of living, but the quality and affordability of housing are dependent on income derived from occupation. - It is more of an outcome of the level of living rather than its primary determinant. *Health* - **Health** is essential for well-being and productivity, but in the context of "level of living" as an economic measure, it is often a consequence of adequate income and access to resources (which stem from occupation) rather than the primary component. - Good health enables productivity, but health status alone does not define the economic level of living without associated income security.
Microbiology
2 questionsRosette formation with sheep RBCs (SRBCs) indicates functioning of -
All are true regarding the development of T-cells, except?
NEET-PG 2013 - Microbiology NEET-PG Practice Questions and MCQs
Question 591: Rosette formation with sheep RBCs (SRBCs) indicates functioning of -
- A. T-cells (Correct Answer)
- B. B-cells
- C. Neutrophils
- D. Monocytes
Explanation: ***T-cells*** - **T-cells** possess specific receptors, like **CD2** on their surface, that can bind to ligands on sheep red blood cells (SRBCs). - This binding leads to the formation of characteristic **rosettes**, where SRBCs cluster around the T-lymphocytes, indicating functional T-cells. *B-cells* - **B-cells** primarily function in **humoral immunity** by producing antibodies and do not typically form rosettes with sheep RBCs. - While B-cells have surface receptors, they are not CD2 and thus do not facilitate this specific type of rosette formation. *Neutrophils* - **Neutrophils** are **phagocytic cells** involved in innate immunity, primarily combating bacterial and fungal infections. - They lack the specific surface receptors (like CD2) required to form rosettes with sheep RBCs. *Monocytes* - **Monocytes** are precursors to macrophages and dendritic cells, involved in phagocytosis and antigen presentation. - They do not possess the necessary surface markers to form rosettes with sheep RBCs.
Question 592: All are true regarding the development of T-cells, except?
- A. T-cells are formed in bone marrow
- B. In lymph nodes, T-cells are found in paracortical area
- C. Maturation of T-cells take place in thymus
- D. T-cells are located in mantle layer of spleen (Correct Answer)
Explanation: ***T-cells are located in mantle layer of spleen*** - The **mantle layer** (or marginal zone) of the spleen is primarily associated with **B-lymphocytes**, which are involved in antibody production. - While T-cells are present in the spleen, they are predominantly found in the **periarteriolar lymphoid sheath (PALS)**, which is part of the white pulp, rather than the mantle layer. *T-cells are formed in bone marrow* - **Hematopoietic stem cells** in the **bone marrow** are the progenitors of all blood cells, including lymphocytes. - These stem cells differentiate into **lymphoid stem cells**, which then travel to the thymus to become T-cells. *Maturation of T-cells take place in thymus* - **T-cell precursors** migrate from the bone marrow to the **thymus**, where they undergo a complex process of differentiation and selection. - In the thymus, T-cells acquire their **T-cell receptors (TCRs)** and undergo positive and negative selection to ensure they are self-MHC restricted and tolerant to self-antigens. *In lymph nodes, T-cells are found in paracortical area* - The **paracortical area** (or paracortex) of the lymph node is the **T-cell zone**, rich in T-lymphocytes and dendritic cells. - This region is crucial for the interaction between T-cells and antigen-presenting cells, initiating adaptive immune responses.
Pediatrics
1 questionsAt what age does clinically significant IgG production begin?
NEET-PG 2013 - Pediatrics NEET-PG Practice Questions and MCQs
Question 591: At what age does clinically significant IgG production begin?
- A. Around 6 months (Correct Answer)
- B. Around 1 year
- C. Around 2 years
- D. Around 3 years
Explanation: ***Around 6 months*** - Maternal IgG levels, which provide **passive immunity**, decrease significantly by 3-6 months of age. - Infants begin to produce their own **clinically significant** levels of IgG around this time, coinciding with the "physiologic nadir" of IgG. *Around 1 year* - While IgG production continues to mature, significant production has already begun by 6 months to replace declining maternal antibodies. - By 1 year, the immune system is more robust, but the initial critical transition occurs earlier. *Around 2 years* - By this age, children generally have a robust adaptive immune response, and the period of vulnerability due to low IgG has passed. - This option is too late for the beginning of clinically significant IgG production. *Around 3 years* - This age is far past the point where children start producing their own significant levels of IgG. - The immune system is well-developed by 3 years, and initial IgG production started much earlier.
Pharmacology
2 questionsMode of excretion of cyclophosphamide is?
Which class of drugs does botulinum toxin mimic in its action?
NEET-PG 2013 - Pharmacology NEET-PG Practice Questions and MCQs
Question 591: Mode of excretion of cyclophosphamide is?
- A. Lung
- B. Liver
- C. Kidney (Correct Answer)
- D. Skin
Explanation: ***Kidney*** - Cyclophosphamide is a **prodrug** that undergoes metabolism in the liver to its active forms. However, both the parent drug and its active metabolites are primarily **excreted renally**. [1] - Renal excretion means that patients with **renal impairment** may require dose adjustments to prevent drug accumulation and increased toxicity. [3] *Lung* - The lungs are primarily involved in **gas exchange** and the elimination of volatile substances, not non-volatile drugs like cyclophosphamide. - While some drugs can be excreted to a minor extent via the lungs, it is not the primary route for **cyclophosphamide**. *Liver* - The liver is the primary site of **metabolism** for cyclophosphamide, where it is converted into active cytotoxic metabolites. [1], [2] - While metabolites are formed here, the liver is not the main organ for the final **elimination** (excretion) of the drug or its metabolites from the body. *Skin* - The skin's role in drug excretion is generally minimal, mainly involving substances excreted in **sweat**, and is not a significant route for cyclophosphamide. - Excretion via the skin is typically very limited for most drugs and does not play a major role in the elimination of **chemotherapeutic agents** like cyclophosphamide.
Question 592: Which class of drugs does botulinum toxin mimic in its action?
- A. Adrenergics
- B. Antiadrenergic
- C. Cholinergics
- D. Anticholinergics (Correct Answer)
Explanation: ***Anticholinergics*** - **Botulinum toxin** inhibits the release of **acetylcholine** from **presynaptic nerve terminals** [2] by preventing vesicle fusion, leading to muscle paralysis [1]. - While the **mechanism differs** (botulinum acts presynaptically, anticholinergics act postsynaptically at receptors), the **functional outcome** is similar: reduced cholinergic neurotransmission. - In terms of **clinical effect** at the neuromuscular junction, both reduce acetylcholine's action, making anticholinergics the closest functional parallel among the given options. *Cholinergics* - **Cholinergics** enhance acetylcholine activity, either by increasing its release, mimicking its effects at receptors, or inhibiting its breakdown. - This is the **opposite** of botulinum toxin's action, which reduces acetylcholine's impact. *Adrenergics* - **Adrenergics** stimulate the **sympathetic nervous system** via **adrenergic receptors** (α and β receptors). - They act on **norepinephrine/epinephrine pathways**, not the cholinergic system where botulinum toxin acts. *Antiadrenergic* - **Antiadrenergic drugs** block **adrenergic receptors** or inhibit sympathetic activity. - These are unrelated to botulinum toxin's effect on **cholinergic neuromuscular transmission**.
Physiology
2 questionsOssicles of middle ear are responsible for which of the following ?
Which immunoglobulin is primarily secreted by the intestine?
NEET-PG 2013 - Physiology NEET-PG Practice Questions and MCQs
Question 591: Ossicles of middle ear are responsible for which of the following ?
- A. Amplification of sound intensity
- B. Reduction of sound intensity
- C. Protecting the inner ear
- D. Reduction of impedance for sound transmission (Correct Answer)
Explanation: ***Reduction of impedance for sound transmission*** - The ossicles (malleus, incus, and stapes) act as a **lever system** to match the impedance between the air-filled outer ear and the fluid-filled inner ear. - This impedance matching ensures that maximum sound energy is transferred to the cochlea, preventing significant **sound reflection**. *Amplification of sound intensity* - While the ossicles do slightly amplify the sound pressure, their primary role is not extensive amplification but rather **impedance matching**. - The amplification achieved is a byproduct of efficient energy transfer, rather than a direct goal of increasing sound intensity for its own sake. *Reduction of sound intensity* - This function is primarily attributed to the **acoustic reflex**, where the middle ear muscles contract to stiffen the ossicular chain in response to loud sounds. - The primary function of the ossicles themselves is to transmit sound efficiently, not to reduce intensity under normal conditions. *Protecting the inner ear* - While the **acoustic reflex** (involving middle ear muscles attached to the ossicles) offers some protection against very loud sounds by stiffening the ossicular chain, this is a separate, reflexive mechanism. - The intrinsic structure and primary mechanical function of the ossicles are centered on efficient sound transmission, not direct physical protection of the inner ear.
Question 592: Which immunoglobulin is primarily secreted by the intestine?
- A. IgG
- B. IgM
- C. IgA (Correct Answer)
- D. IgD
Explanation: **IgA** - **Secretory IgA** is the dominant immunoglobulin in mucosal secretions, including those of the intestine. - It plays a crucial role in providing **local immunity** by preventing microbial adherence and neutralizing toxins on mucosal surfaces. *IgG* - **IgG** is the most abundant immunoglobulin in serum and plays a major role in systemic immunity, including opsonization and complement activation. - While some IgG is found in secretions, it is not the primary immunoglobulin secreted by the intestine. *IgM* - **IgM** is a pentameric immunoglobulin, primarily found in blood and lymph, where it is very effective in activating the complement system and agglutinating antigens. - Although it can be found at mucosal surfaces in small amounts, it is not the principal secreted antibody in the intestine. *IgD* - **IgD** is primarily found on the surface of naive B lymphocytes, where it functions as a B cell receptor. - Its role in secreted form is minimal, and it is not significantly secreted into the intestine or other bodily fluids.