NEET-PG 2015 Practice Questions

Q: In the context of blood pressure regulation, where are baroreceptors primarily located?

Tunica adventitia. ***Tunica adventitia*** - **Baroreceptors** are specialized mechanoreceptive nerve endings that detect changes in blood pressure by sensing arterial wall stretch. - These sensory nerve endings are primarily located in the **tunica adventitia** (outermost layer) of the **carotid sinus** and **aortic arch** [1]. - The adventitia contains the **nerve fibers and endings** (including baroreceptors), as well as the vasa vasorum and connective tissue supporting the vessel wall [1]. - The nerve terminals extend from the adventitia toward the adventitial-medial border where they sense wall tension changes. *Tunica media* - The **tunica media** is the middle layer composed of **smooth muscle cells** and elastic fibers. - While this layer responds to stretch and changes thickness with blood pressure variations, it does **not contain nerve endings or baroreceptors** [1]. - The media is responsible for vasoconstriction and vasodilation but lacks the sensory innervation needed for baroreception. *Tunica intima* - The **tunica intima** is the innermost layer lined by **endothelial cells**. - Its primary functions include providing a smooth surface for blood flow and regulating vascular permeability. - This layer does not house baroreceptors or other mechanoreceptive nerve endings. *None of the options* - This option is incorrect because **tunica adventitia** is indeed the correct location of baroreceptors. - The adventitia contains the neural elements necessary for blood pressure sensing in these specialized arterial regions [1].

Q: IFN-gamma is produced by

T-cells. ***T-cells*** - **Interferon-gamma (IFN-γ)** is a crucial cytokine primarily produced by **activated T-lymphocytes**, especially **Th1 cells** and **cytotoxic T lymphocytes (CTLs)**. - Natural killer (NK) cells also produce **IFN-γ**, which plays a key role in **antiviral** and **antitumor immunity**, as well as in promoting **Type 1 immune responses**. *Macrophages* - While macrophages are **responsive to IFN-γ** (e.g., becoming activated), they are not the primary producers of this cytokine. - Macrophages primarily produce other cytokines such as **IL-1, IL-6, TNF-alpha**, and **IL-12** in response to infection or inflammation. *Neutrophils* - **Neutrophils** are key phagocytes in the innate immune system and are primarily involved in engulfing and killing pathogens. - They are not known to be a significant source of **IFN-γ** production; their main defensive mechanisms involve **phagocytosis**, **degranulation**, and **NETosis**. *B-cells* - **B-cells** are central to humoral immunity, specializing in **antibody production** and acting as **antigen-presenting cells**. - They generally do not produce **IFN-γ**; instead, their cytokine repertoire includes **IL-10**, **IL-6**, and **lymphotoxin**.

Q: Obliterative endarteritis in vasa vasorum is seen in -

Tertiary Syphilis. ***Tertiary Syphilis*** - **Obliterative endarteritis** of the **vasa vasorum** is a hallmark pathological finding in tertiary syphilis, particularly affecting the **aorta**. - This inflammation and occlusion of the small blood vessels supplying the aorta lead to **ischemic injury** of the aortic wall, causing **aneurysms** and **aortic regurgitation**. *Essential Hypertension* - While hypertension can lead to vascular changes like **arteriolosclerosis** and **hyperplastic arteriolosclerosis**, it does not typically involve obliterative endarteritis of the vasa vasorum. - The vascular damage in essential hypertension is more generalized to smaller arteries and arterioles, not specifically the vasa vasorum. *Systemic Lupus Erythematosus* - SLE is an **autoimmune disease** that can cause **vasculitis**, but the specific pattern of obliterative endarteritis of the vasa vasorum is not characteristic. - Vascular involvement in SLE is diverse, ranging from small vessel vasculitis to accelerated atherosclerosis, but distinct from syphilitic changes. *Pulmonary Tuberculosis* - Tuberculosis is primarily an **infectious granulomatous disease** affecting the lungs and other organs; it does not typically cause obliterative endarteritis of the vasa vasorum. - Although it can cause vascular complications like **aneurysms** (e.g., Rasmussen's aneurysm) due to erosion, the underlying mechanism is not the same as syphilitic changes.

Q: Which genetic condition is considered the most lethal due to monosomy?

Autosomal monosomy. ***Autosomal monosomy*** - **Autosomal monosomy** is the most lethal form of monosomy because it involves the loss of an entire autosome, leading to a severe imbalance in gene dosage. [1] - The human body cannot typically survive with the loss of a whole autosome, resulting in early embryonic or fetal demise. [1] *Chromosomal monosomy* - This is a broader term that includes both **autosomal monosomy** and **sex chromosome monosomy**. - While many forms of chromosomal monosomy are lethal, **sex chromosome monosomy (e.g., Turner syndrome)** is survivable, making the general term "chromosomal monosomy" less specific for the *most lethal* condition. [1] *Autosomal trisomy* - **Autosomal trisomy** involves an extra copy of an autosome (e.g., Trisomy 21 for Down syndrome), which, while causing significant health issues, is generally less lethal than the complete loss of an autosome. [1] - Many individuals with autosomal trisomies can survive to birth and beyond, unlike most cases of autosomal monosomy. [1] *Chromosomal trisomy* - This refers to having an extra copy of any chromosome, including **autosomes** and **sex chromosomes**. - While conditions like **Trisomy 13 (Patau syndrome)** and **Trisomy 18 (Edwards syndrome)** are highly lethal, the presence of *extra* genetic material is typically less universally lethal than the *absence* of an entire autosome. [1] **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Genetic Disorders, pp. 168-169.

Q: Which of the following is an action of muscarinic cholinergic receptors?

Decreased heart rate. ***Decreased heart rate*** - Activation of **muscarinic cholinergic receptors (M2 receptors)** in the heart leads to a decrease in heart rate and conduction velocity. - This effect is mediated by the **vagus nerve (parasympathetic nervous system)**, which releases acetylcholine to act on these receptors. - This is the **most characteristic and clinically significant cardiovascular effect** of muscarinic receptor activation, making it the expected answer. *Skeletal muscle contraction* - **Skeletal muscle contraction** is mediated by **nicotinic acetylcholine receptors (nAChRs)** at the **neuromuscular junction**, NOT muscarinic receptors. - Nicotinic receptors are **ligand-gated ion channels** that cause direct depolarization and muscle contraction when activated. - This is the only option that is **NOT a muscarinic receptor action**. *Acid secretion in stomach* - **Gastric acid secretion** IS mediated by **M3 muscarinic receptors** on parietal cells. - Acetylcholine from the vagus nerve directly stimulates parietal cells and also stimulates histamine release from enterochromaffin-like cells. - While this is a valid muscarinic action, in the context of distinguishing muscarinic effects, **cardiac effects** (decreased heart rate) are more emphasized as the classic teaching point. *Salivation and lacrimation* - **Salivation and lacrimation** ARE mediated by **M3 muscarinic receptors** in exocrine glands. - These are classic parasympathetic/muscarinic effects taught in physiology. - However, when distinguishing key muscarinic actions, **M2 receptor-mediated cardiac effects** are typically highlighted as the primary cardiovascular manifestation, while M3 effects on glands are secondary teaching points.

Q: Which of the following is an example of topical administration producing only local effects (not systemic)?

Topical corticosteroid cream. ***Topical corticosteroid cream*** - When applied to the skin for conditions like dermatitis, topical corticosteroids primarily exert their effects at the site of application, reducing **local inflammation** and itching. - While systemic absorption can occur with potent steroids over large areas, typical use aims for **localized action** without significant systemic effects. *Sublingual nitroglycerin* - This route is designed for **rapid systemic absorption** through the oral mucosa, bypassing first-pass metabolism to quickly treat angina. - The goal is a **widespread vasodilatory effect** throughout the body, not a local one within the mouth. *Transdermal patch* - Transdermal patches, such as those for nicotine or fentanyl, are specifically designed to deliver medication **systemically** through the skin into the bloodstream over a prolonged period. - They provide a **sustained release** and systemic therapeutic effect throughout the body. *Rectal diazepam* - Administered rectally, diazepam is absorbed into the systemic circulation to produce **CNS effects** such as sedation, anxiolysis, or anticonvulsant activity. - Although the administration is local, the intended clinical effect is **systemic** and widespread throughout the body.

Q: Rebound increase in gastric acid secretion after stopping proton pump inhibitor therapy is due to?

Hypergastrinemia. ***Hypergastrinemia*** - Proton pump inhibitors (PPIs) create a state of **hypochlorhydria** (reduced stomach acid), which in turn stimulates the **G cells** in the stomach to produce more **gastrin**. - This elevated gastrin level leads to a compensatory increase in the number and activity of **parietal cells**, causing a rebound hypersecretion of acid when PPI therapy is discontinued. *Parietal cell hyperplasia* - While parietal cell hyperplasia can occur, it is a consequence of chronic **hypergastrinemia**, not the primary driver of rebound acid secretion. - The direct effect of increased gastrin stimulating existing parietal cells is more immediate and significant for the rebound phenomenon. *Increased histamine release* - Elevated histamine release from **enterochromaffin-like (ECL) cells** is a downstream effect of hypergastrinemia, as gastrin stimulates ECL cells. - While increased histamine contributes to acid secretion, the root cause for its increase in this context is the **hypergastrinemia** induced by PPIs. *Hypersensitivity of Ach receptors* - **Acetylcholine (Ach) receptors** on parietal cells are involved in direct neural stimulation of acid secretion. - There is no evidence that stopping PPIs causes an increased sensitivity of these receptors, or that this is the primary mechanism of rebound acid secretion.

Q: 'Flare' in Triple response is mediated by :

Axon reflex. ***Axon reflex*** - The "flare" component of the triple response is caused by an **axon reflex**, where sensory nerve endings release **vasoactive neuropeptides** such as substance P and calcitonin gene-related peptide (CGRP). - These neuropeptides cause **vasodilation** in the surrounding area, leading to the characteristic red, irregularly shaped halo around the wheal. *Arteriolar dilation* - While arteriolar dilation is a component of the triple response and contributes to the **redness (flush)** and **flare**, it is not the direct mediator of the flare itself. - The initial arteriolar dilation is primarily due to **histamine** acting directly on the vessels, whereas the flare is a broader, neurally mediated spread of vasodilation. *Histamine release* - **Histamine** release from mast cells is the primary mediator of the initial **redness (flush)** and the formation of the **wheal** (swelling due to capillary permeability). - While histamine plays a role in the overall response, it does not directly mediate the "flare" component, which involves neuronal signaling via the axon reflex. *Local hormones* - While various **local mediators** (which could be broadly considered "local hormones" in a sense) are involved in inflammatory responses, the specific term "local hormones" is too general and does not precisely describe the mechanism of the flare. - The axon reflex, involving specific **neuropeptides**, is the precise mechanism for the flare, not a general category of local hormones.

Q: Which of the following parameters indicates the elimination of CO2 from the lungs?

PaCO2. ***PaCO2*** - **Partial pressure of carbon dioxide in arterial blood (PaCO2)** directly reflects the efficiency of **alveolar ventilation**, which is the process of eliminating CO2 from the lungs. - When CO2 elimination is adequate, PaCO2 remains within the normal range (35-45 mmHg); higher or lower values indicate ventilatory impairment or hyperventilation, respectively. *PaO2* - **PaO2** measures the partial pressure of **oxygen in arterial blood** and indicates oxygenation, not the efficiency of carbon dioxide elimination. - While CO2 elimination and oxygenation are interdependent, **PaO2** primarily reflects how well oxygen is being transported from the lungs to the blood. *pH* - **pH** indicates the **acidity or alkalinity of the blood**, which is influenced by both respiratory (CO2) and metabolic (bicarbonate) components. - Although CO2 elimination affects pH through the carbonic acid-bicarbonate buffer system, pH itself is an overall measure of acid-base balance, not a direct indicator of CO2 elimination. *HCO3 level* - **Bicarbonate (HCO3-)** is a **metabolic component** of the acid-base balance, primarily regulated by the kidneys. - While it helps buffer CO2-induced acid changes, HCO3 level alone does not directly reflect the efficiency of CO2 elimination from the lungs.

Question 1

In the context of blood pressure regulation, where are baroreceptors primarily located?

Accepted Answer

Tunica adventitia

Answer

Tunica intima

Answer

None of the options

Answer

Tunica media

Question 2

What is a key similarity between the processes of replication and transcription?

Accepted Answer

Involve phosphodiester bond formation with elongation occurring in the 5' - 3' direction.

Answer

Use RNA primers for initiation.

Answer

Use ribonucleotides as precursors.

Answer

Are semi-conservative events.

Question 3

IFN-gamma is produced by

Accepted Answer

T-cells

Answer

Macrophages

Answer

Neutrophils

Answer

B-cells

Question 4

Obliterative endarteritis in vasa vasorum is seen in -

Accepted Answer

Tertiary Syphilis

Answer

Essential Hypertension

Answer

Systemic Lupus Erythematosus

Answer

Pulmonary Tuberculosis

Question 5

Which genetic condition is considered the most lethal due to monosomy?

Accepted Answer

Autosomal monosomy

Answer

Chromosomal monosomy

Answer

Autosomal trisomy

Answer

Chromosomal trisomy

Question 6

Which of the following is an action of muscarinic cholinergic receptors?

Accepted Answer

Decreased heart rate

Answer

Skeletal muscle contraction

Answer

Acid secretion in stomach

Answer

Salivation and lacrimation

Question 7

Which of the following is an example of topical administration producing only local effects (not systemic)?

Accepted Answer

Topical corticosteroid cream

Answer

Sublingual nitroglycerin

Answer

Transdermal patch

Answer

Rectal diazepam

Question 8

Rebound increase in gastric acid secretion after stopping proton pump inhibitor therapy is due to?

Accepted Answer

Hypergastrinemia

Answer

Parietal cell hyperplasia

Answer

Increased histamine release

Answer

Hypersensitivity of Ach receptors

Question 9

'Flare' in Triple response is mediated by :

Accepted Answer

Axon reflex

Answer

Arteriolar dilation

Answer

Histamine release

Answer

Local hormones

Question 10

Which of the following parameters indicates the elimination of CO2 from the lungs?

Accepted Answer

PaCO2

Answer

pH

Answer

PaO2

Answer

HCO3 level

NEET-PG 2015

Anatomy

Biochemistry

Microbiology

Pathology

Pharmacology

Physiology