Anatomy
1 questionsWhat is the approximate number of cones in the human retina?
NEET-PG 2013 - Anatomy NEET-PG Practice Questions and MCQs
Question 381: What is the approximate number of cones in the human retina?
- A. Approximately 3-5 million cones (Correct Answer)
- B. Approximately 25-50 million cones
- C. Approximately 50-100 million cones
- D. Approximately 10-20 million cones
Explanation: Approximately 3-5 million cones - The human retina contains roughly **4.5 million cones**, concentrated in the **fovea**, which is responsible for **high-acuity vision** and color perception [1]. - Cones are light-sensitive cells that detect **fine details** and are essential for vision in **bright light conditions** [1]. *Approximately 10-20 million cones* - This range is significantly higher than the actual number of cones found in the human retina. - While there are millions of photoreceptors, the *majority are rods*, not cones [1]. *Approximately 25-50 million cones* - This figure vastly *overestimates* the number of cones in the human eye. - The total number of photoreceptor cells (rods and cones combined) in the retina typically ranges from **100-125 million** [1]. *Approximately 50-100 million cones* - This range is incorrect as it refers more closely to the *total number of rods* in the human retina, which is about **90-120 million** [1]. - Cones constitute a much smaller proportion of the total photoreceptor population [1].
Biochemistry
1 questionsWhich type of RNA is primarily involved in gene silencing?
NEET-PG 2013 - Biochemistry NEET-PG Practice Questions and MCQs
Question 381: Which type of RNA is primarily involved in gene silencing?
- A. rRNA
- B. tRNA
- C. miRNA (Correct Answer)
- D. mRNA
Explanation: ***miRNA*** - **miRNA** (microRNA) is a small non-coding RNA molecule that plays a crucial role in **post-transcriptional regulation of gene expression**. - It functions by binding to complementary messenger RNA (mRNA) molecules, leading to **mRNA degradation** or **inhibition of translation**, thereby silencing genes. - miRNA is the primary RNA type involved in **gene silencing** through the RNA interference (RNAi) pathway. *rRNA* - **rRNA** (ribosomal RNA) is a primary component of **ribosomes**, the cellular machinery responsible for protein synthesis. - Its main function is to **catalyze peptide bond formation** and provide structural integrity to the ribosome, not gene silencing. *tRNA* - **tRNA** (transfer RNA) is responsible for carrying specific **amino acids** to the ribosome during protein synthesis. - It acts as an adapter molecule, translating the **genetic code** in mRNA into an amino acid sequence. *mRNA* - **mRNA** (messenger RNA) carries genetic information from **DNA to ribosomes** for protein synthesis. - While mRNA can be targeted by gene silencing mechanisms (like miRNA), it is not the RNA type that performs the silencing function itself.
Internal Medicine
1 questionsWhich of the following is not an obstructive lung disease?
NEET-PG 2013 - Internal Medicine NEET-PG Practice Questions and MCQs
Question 381: Which of the following is not an obstructive lung disease?
- A. Emphysema
- B. Interstitial fibrosis (Correct Answer)
- C. Asthma
- D. Bronchitis
Explanation: ***Interstitial fibrosis*** - **Interstitial fibrosis** is a **restrictive lung disease**, characterized by **reduced lung elasticity** and lung volumes, rather than airway obstruction [1]. - In this condition, the **lung tissue becomes scarred and stiff**, making it difficult to expand fully during inspiration [1]. *Emphysema* - **Emphysema** is a classic **obstructive lung disease** caused by the destruction of the **alveolar walls**, leading to enlarged air spaces and loss of elastic recoil [3]. - This destruction results in **airflow limitation**, particularly during exhalation, as airways collapse prematurely. *Asthma* - **Asthma** is an **obstructive lung disease** characterized by **reversible airway inflammation**, bronchoconstriction, and increased mucus production [2]. - These factors lead to **episodic airflow obstruction**, making it difficult to breathe, especially during exacerbations [2]. *Bronchitis* - **Bronchitis**, particularly **chronic bronchitis**, is an **obstructive lung disease** defined by chronic inflammation of the bronchi. - This inflammation causes **mucus hypersecretion** and narrowing of the airways, leading to persistent cough and airflow limitation.
Pathology
3 questionsAll are growth promoting oncogenes except ?
Curschmann's spirals are seen in which condition?
Which of the following is a primary pleural tumor?
NEET-PG 2013 - Pathology NEET-PG Practice Questions and MCQs
Question 381: All are growth promoting oncogenes except ?
- A. FGF
- B. PDGF
- C. TGF-α
- D. TGF-β (Correct Answer)
Explanation: ***TGF-p*** - **TGF-p (Transforming Growth Factor beta)** is primarily known as a **growth inhibitory** factor rather than a promoting oncogene. - It plays a crucial role in **cell differentiation**, **apoptosis**, and inhibits cell proliferation, counteracting the effects of other oncogenes. *TGF-a* - **TGF-a (Transforming Growth Factor alpha)** is a **growth factor** that stimulates cell proliferation and is involved in various cancers [1][2]. - It binds to the **EGF receptor**, promoting growth and tumor development. *PDGF* - **PDGF (Platelet-Derived Growth Factor)** acts as a potent **mitogen** for connective tissue cells and is involved in wound healing and tumor growth [2][4]. - It plays a central role in promoting cell proliferation and migration, contributing to cancer progression [4]. *FGF* - **FGF (Fibroblast Growth Factor)** promotes mitosis and is crucial in **angiogenesis**, wound healing, and several developmental processes [2]. - Its overexpression is linked to various tumors, making it a significant oncogenic growth promoter [2][3]. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. With Illustrations By, pp. 30-31. [2] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Neoplasia, p. 292. [3] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Neoplasia, pp. 292-293. [4] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. With Illustrations By, pp. 31-32.
Question 382: Curschmann's spirals are seen in which condition?
- A. Bronchiectasis
- B. Chronic bronchitis
- C. Wegener's granulomatosis
- D. Bronchial asthma (Correct Answer)
Explanation: ***Bronchial asthma*** - **Curschmann's spirals** are spiral-shaped mucus plugs found in the sputum of patients with **bronchial asthma**. - They represent casts from small bronchi and are formed from **mucus and cellular debris** within the airways during an asthmatic exacerbation. *Bronchiectasis* - Characterized by **permanent abnormal dilation** of the bronchi due to chronic inflammation and infection, leading to productive cough and recurrent respiratory infections. - While it involves mucous production, it is typically associated with **purulent sputum** due to bacterial colonization, not necessarily Curschmann's spirals. *Chronic bronchitis* - Defined clinically by a **chronic productive cough** for at least three months in each of two successive years, without other causes. - Involves mucus hypersecretion and inflammation, but **Curschmann's spirals are not a characteristic finding** compared to asthma. *Wegener's granulomatosis (Granulomatosis with Polyangiitis)* - This is a systemic **vasculitis** affecting small to medium-sized blood vessels, typically involving the upper and lower respiratory tracts and kidneys. - Its pulmonary manifestations include **nodules, cavities, and diffuse alveolar hemorrhage**, and sputum findings are related to inflammation and bleeding, not Curschmann's spirals.
Question 383: Which of the following is a primary pleural tumor?
- A. Mesothelioma (Correct Answer)
- B. Myxoma
- C. Lipoma
- D. None of the options
Explanation: ***Mesothelioma*** - Mesothelioma is a **primary malignant tumor** of the pleura [1], commonly associated with **asbestos exposure** [2]. - It typically presents with symptoms like **pleuritic chest pain**, dyspnea, and pleural effusion. *Myxoma* - Myxoma is a **benign tumor** primarily found in the **heart**, particularly in the left atrium, not in the pleura. - It does not arise from pleural tissue and lacks the **malignant characteristics** of mesothelioma. *All* - This option suggests that multiple tumors can be primary pleural tumors, which is incorrect as only mesothelioma is recognized as such. - Other tumors like myxoma and lipoma do not originate in the pleura and thus cannot be classified as primary pleural tumors. *Lipoma* - Lipoma is a **benign tumor** made up of adipose tissue [3] and is typically found in *subcutaneous tissue*, not the pleural cavity. - It does not have the malignant potential or association with pleural disease that characterizes mesothelioma. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. The Lung, pp. 728-729. [2] Cross SS. Underwood's Pathology: A Clinical Approach. 6th ed. Common Clinical Problems From Respiratory Tract Disease, pp. 339-340. [3] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Bones, Joints, and Soft Tissue Tumors, p. 1222.
Physiology
2 questionsCushing reflex is associated with all except?
Which of the following does not have sympathetic noradrenergic fibers?
NEET-PG 2013 - Physiology NEET-PG Practice Questions and MCQs
Question 381: Cushing reflex is associated with all except?
- A. Irregular respiration
- B. Hypotension (Correct Answer)
- C. Increased intracranial pressure
- D. Bradycardia
Explanation: ***Hypotension*** - The **Cushing reflex** is a compensatory response to increased intracranial pressure (ICP) aiming to maintain cerebral perfusion, which typically involves **hypertension**, not hypotension. - While prolonged or severe ICP can lead to decompensation and eventual hypotension, it is not a direct component of the reflex itself. *Increased intracranial pressure* - The **Cushing reflex** is triggered by an elevation in **intracranial pressure (ICP)**, as the body attempts to maintain blood flow to the brain. - This increased ICP reduces cerebral perfusion pressure, prompting a systemic response to raise mean arterial pressure. *Bradycardia* - **Bradycardia** is a classic component of the **Cushing reflex**, occurring as a compensatory response to the reflex hypertension. - The increased arterial blood pressure stimulates carotid and aortic baroreceptors, leading to a vagal response that slows the heart rate. *Irregular respiration* - **Irregular respiration** is another key component of the **Cushing reflex**, often manifesting as **Cheyne-Stokes breathing** or **ataxic breathing**. - This respiratory dysregulation is due to direct compression and dysfunction of the brainstem, specifically the medullary respiratory centers, caused by increased ICP.
Question 382: Which of the following does not have sympathetic noradrenergic fibers?
- A. Heart
- B. Eye
- C. Sweat gland (Correct Answer)
- D. Blood vessels
Explanation: ***Sweat gland*** - While sweat glands are innervated by the **sympathetic nervous system**, their postganglionic fibers are **cholinergic**, releasing **acetylcholine** rather than noradrenaline. - This is an important exception where sympathetic stimulation leads to acetylcholine release, causing sweating. *Blood vessels* - Most blood vessels, particularly resistance vessels such as **arterioles**, receive substantial **sympathetic noradrenergic innervation** that causes vasoconstriction. - This sympathetic tone is crucial for regulating **blood pressure** and distributing blood flow. *Heart* - The heart is richly innervated by **sympathetic noradrenergic fibers** that increase **heart rate**, **contractility**, and **conduction velocity** via beta-1 adrenergic receptors. - This makes noradrenaline a key neurotransmitter in the sympathetic regulation of cardiac function. *Eye* - The eye receives sympathetic noradrenergic innervation primarily to the **dilator pupillae muscle**, causing **mydriasis** (pupil dilation) upon activation. - These fibers also contribute to the sympathetic control of the **tarsal muscle** (Müller's muscle) in the eyelid.
Psychiatry
2 questionsWhich of the following is not a characteristic of Fragile X syndrome?
What is the name of the syndrome associated with the deletion of chromosome 22?
NEET-PG 2013 - Psychiatry NEET-PG Practice Questions and MCQs
Question 381: Which of the following is not a characteristic of Fragile X syndrome?
- A. Large nose (Correct Answer)
- B. Large ear
- C. Large testis
- D. Large head
- E. Long narrow face
Explanation: **Large nose** - **Large nose** is generally not considered a characteristic feature of **Fragile X syndrome**. - While individuals with Fragile X syndrome have distinct facial features, a prominent or large nose is not typically among them. *Large head* - **Macrocephaly** (large head circumference) is a recognized physical feature in many individuals with **Fragile X syndrome**. - This characteristic often becomes more apparent in infancy and childhood. *Large ear* - **Large, prominent ears** are a very common and classic physical characteristic observed in individuals with **Fragile X syndrome**. - This feature is often noted during developmental assessments. *Large testis* - **Macro-orchidism** (enlarged testes) is a hallmark physical characteristic of **Fragile X syndrome** in post-pubertal males. - This is a highly specific finding and a key diagnostic pointer for the syndrome in adolescent and adult males. *Long narrow face* - **Long, narrow face** with a prominent forehead and jaw is a typical facial feature of **Fragile X syndrome**. - This characteristic facial appearance is part of the recognizable phenotype of the syndrome.
Question 382: What is the name of the syndrome associated with the deletion of chromosome 22?
- A. Down syndrome
- B. Di George syndrome (Correct Answer)
- C. Turner syndrome
- D. Klinefelter syndrome
- E. Prader-Willi syndrome
Explanation: ***Di George syndrome*** - Di George syndrome, also known as **22q11.2 deletion syndrome**, is caused by a deletion on the long arm of chromosome 22. - This syndrome is associated with varied clinical features, including **congenital heart defects**, **thymic hypoplasia** (leading to immune deficiencies), **hypocalcemia** due to parathyroid hypoplasia, and characteristic facial features. *Down syndrome* - Down syndrome is caused by a **trisomy of chromosome 21**, meaning there's an extra copy of chromosome 21. - It is characterized by intellectual disability, distinctive facial features, and developmental delays, and is not associated with chromosome 22 deletion. *Turner syndrome* - Turner syndrome is a chromosomal condition affecting females, characterized by the partial or complete absence of one of the **X chromosomes (45, X0)**. - It leads to short stature, ovarian dysfunction, and characteristic physical features, unrelated to chromosome 22. *Klinefelter syndrome* - Klinefelter syndrome is a chromosomal disorder in males resulting from an extra **X chromosome (47, XXY)**. - Individuals often experience hypogonadism, reduced fertility, and abnormal body proportions, which is distinct from a deletion on chromosome 22. *Prader-Willi syndrome* - Prader-Willi syndrome is caused by a **deletion of paternal chromosome 15q11-q13** or maternal uniparental disomy. - It presents with hypotonia, hyperphagia, obesity, intellectual disability, and hypogonadism, unrelated to chromosome 22 deletion.