Anatomy
1 questionsFrey's syndrome occurs due to aberrant regeneration of parasympathetic nerve fibers following parotid surgery, leading to gustatory sweating. The nerve directly involved in this aberrant reinnervation is:
NEET-PG 2019 - Anatomy NEET-PG Practice Questions and MCQs
Question 161: Frey's syndrome occurs due to aberrant regeneration of parasympathetic nerve fibers following parotid surgery, leading to gustatory sweating. The nerve directly involved in this aberrant reinnervation is:
- A. Trigeminal nerve
- B. Facial nerve
- C. GlossoPharyngeal nerve
- D. Auriculotemporal nerve (Correct Answer)
Explanation: ***Auriculotemporal nerve*** - Frey's syndrome, or **gustatory sweating**, occurs due to damage to the **auriculotemporal nerve**, typically during parotidectomy. - Aberrant regeneration leads to misdirection of parasympathetic fibers meant for the parotid gland to the sweat glands in the preauricular and temporal regions. *Trigeminal nerve* - The trigeminal nerve (CN V) is primarily responsible for **sensory innervation of the face** and **motor innervation of the muscles of mastication**. - It does not directly provide secretomotor innervation to the parotid gland or sweat glands. *Facial nerve* - The facial nerve (CN VII) innervates the **muscles of facial expression** and provides taste sensation to the anterior two-thirds of the tongue, and secretomotor innervation to the submandibular and sublingual glands. - While it passes through the parotid gland, it does not provide secretomotor innervation to the parotid gland itself. *GlossoPharyngeal nerve* - The glossopharyngeal nerve (CN IX) provides presynaptic parasympathetic fibers to the **otic ganglion**, which then synapse with postsynaptic fibers carried by the auriculotemporal nerve to the parotid gland. - Although it is the origin of the parasympathetic innervation for the parotid, the direct aberrant reinnervation in Frey's syndrome involves the auriculotemporal nerve, not the glossopharyngeal nerve itself.
Anesthesiology
1 questionsWhich IV anesthetic does not cause cardiac depression?
NEET-PG 2019 - Anesthesiology NEET-PG Practice Questions and MCQs
Question 161: Which IV anesthetic does not cause cardiac depression?
- A. Propofol
- B. Etomidate (Correct Answer)
- C. Thiopentone
- D. Methohexital
Explanation: **Etomidate** - **Etomidate** is known for its **minimal cardiovascular effects**, making it a preferred choice in patients with **pre-existing cardiac disease** or hemodynamic instability. - Unlike other IV anesthetics, it causes very little change in **heart rate**, **blood pressure**, or **cardiac output**. *Propofol* - **Propofol** frequently causes **dose-dependent myocardial depression** and **vasodilation**, leading to significant decreases in blood pressure. - Its cardiovascular effects can be problematic in patients with compromised cardiac function. *Thiopentone* - **Thiopentone**, a barbiturate, typically causes **dose-dependent cardiovascular depression**, including reduced **myocardial contractility** and **vasodilation**. - This can result in a decrease in **blood pressure** and **cardiac output**. *Methohexital* - **Methohexital**, another barbiturate, also causes **cardiovascular depression** similar to thiopentone. - It can lead to decreased **blood pressure** due to both **myocardial depression** and **peripheral vasodilation**.
Biochemistry
1 questionsTrue regarding mitochondrial DNA is:
NEET-PG 2019 - Biochemistry NEET-PG Practice Questions and MCQs
Question 161: True regarding mitochondrial DNA is:
- A. Linear double stranded
- B. All respiratory proteins are synthesized within mitochondria itself
- C. Inherited from mother (Correct Answer)
- D. Low mutation rate
Explanation: ***Inherited from mother*** - **Mitochondrial DNA (mtDNA)** is exclusively inherited from the mother because the sperm's mitochondria are typically destroyed after fertilization or do not enter the oocyte. - This **maternal inheritance pattern** makes mtDNA useful for tracing lineage and studying human population movements. *Linear double stranded* - **Mitochondrial DNA** is typically **circular**, not linear, and double-stranded, similar to a plasmid in bacteria. - **Linear DNA** is characteristic of nuclear chromosomes in eukaryotes. *All respiratory proteins are synthesized within mitochondria itself* - While mitochondria contain their own ribosomes and synthesize some proteins, the majority of **respiratory chain proteins** are encoded by **nuclear DNA** and imported into the mitochondria. - The **mitochondrial genome** encodes only a small fraction of the proteins necessary for mitochondrial function, primarily components of the electron transport chain. *Low mutation rate* - **Mitochondrial DNA** has a **higher mutation rate** compared to nuclear DNA due to a less robust DNA repair system and exposure to reactive oxygen species generated during oxidative phosphorylation. - The high mutation rate can contribute to mitochondrial diseases and can also be used in evolutionary studies.
Microbiology
1 questionsMHC II is associated with:-
NEET-PG 2019 - Microbiology NEET-PG Practice Questions and MCQs
Question 161: MHC II is associated with:-
- A. Red blood cells
- B. Antigen presenting cells (Correct Answer)
- C. Platelets
- D. Epithelial cells
Explanation: ***Antigen presenting cells*** - **MHC II (Major Histocompatibility Complex class II)** molecules are primarily expressed on the surface of professional **antigen-presenting cells (APCs)**. - APCs, such as **macrophages**, **dendritic cells**, and **B lymphocytes**, use MHC II to present **extracellularly derived antigens** to **CD4+ T helper cells**. *Red blood cells* - **Red blood cells (RBCs)** are anucleated and lack MHC molecules entirely. - Their primary function is **oxygen transport**, not immune cell communication. *Platelets* - **Platelets** are cell fragments involved in **hemostasis** (blood clotting). - They do not express MHC class II molecules as they are not involved in antigen presentation. *Epithelial cells* - Most **epithelial cells** primarily express **MHC class I** molecules to present **intracellular antigens** to **CD8+ cytotoxic T cells**. - They do not typically express MHC class II unless under specific inflammatory conditions, and even then, not as their primary function.
Pathology
3 questionsCharacteristic feature of hypertrophic obstructive cardiomyopathy is:
Which chamber of the heart is enlarged first in a patient with McCallum patch?
Cholesterol gallstones are made up of:-
NEET-PG 2019 - Pathology NEET-PG Practice Questions and MCQs
Question 161: Characteristic feature of hypertrophic obstructive cardiomyopathy is:
- A. Increased size of ventricle
- B. Asymmetric septal hypertrophy (Correct Answer)
- C. Normal myofiber arrangement
- D. Increased size of atria
Explanation: ***Asymmetric septal hypertrophy*** - This is the hallmark feature of **hypertrophic obstructive cardiomyopathy (HOCM)**, where the **interventricular septum** thickens disproportionately more than the free wall of the left ventricle [1], [2]. - This septal thickening can lead to **left ventricular outflow tract obstruction**, particularly during systole, obstructing blood flow out of the heart [1]. *Increased size of ventricle* - While the left ventricle may appear enlarged in some dimensions due to hypertrophy, the primary characteristic is specifically **asymmetric thickening of the septum**, not a generalized increase in ventricular size [2]. - In other forms of cardiomyopathy, such as dilated cardiomyopathy, a global increase in ventricular size is observed, which is distinct from HOCM. *Normal myofiber arrangement* - A characteristic microscopic feature of HOCM is **myocardial disarray**, where cardiac muscle fibers are abnormally arranged instead of their usual parallel alignment [1]. - This disorganized arrangement contributes to the impaired function and electrical instability seen in HOCM. *Increased size of atria* - While **left atrial enlargement** can be a secondary finding in HOCM due to increased left ventricular end-diastolic pressure and impaired diastolic filling, it is not the primary or characteristic feature defining the condition [1]. - The fundamental pathology of HOCM lies in the specific hypertrophy of the ventricular myocardium, particularly the septum. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. The Heart, pp. 577-578. [2] Cross SS. Underwood's Pathology: A Clinical Approach. 6th ed. Common Clinical Problems From Cardiovascular Disease, pp. 303-304.
Question 162: Which chamber of the heart is enlarged first in a patient with McCallum patch?
- A. Left atrium (Correct Answer)
- B. Left ventricle
- C. Right atrium
- D. Right ventricle
Explanation: ***Left atrium*** - A **McCallum patch** is a thickened, often irregular endocardial lesion found in the **left atrium**. - It results from the jet lesion of **mitral regurgitation**, indicating the left atrium has been subjected to increased volume and pressure leading to enlargement [1]. *Left ventricle* - While **mitral regurgitation** can eventually lead to **left ventricular enlargement** (due to volume overload), the primary chamber affected by the regurgitant jet causing the McCallum patch is the left atrium. - Left ventricular enlargement is a later consequence, not the first chamber to show this specific lesion. *Right atrium* - The **right atrium** is affected by conditions like **tricuspid regurgitation** or **pulmonary hypertension**, which are unrelated to mitral valve disease or McCallum patches. - It handles systemic venous return, separate from the left-sided circulation involved in mitral pathology. *Right ventricle* - The **right ventricle** is primarily impacted by conditions affecting the **pulmonary circulation** or **tricuspid valve**. - It fills from the right atrium and pumps blood to the lungs, making it unlikely to be the first chamber enlarged in the context of a McCallum patch from mitral regurgitation. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Diseases of Infancy and Childhood, pp. 533-534.
Question 163: Cholesterol gallstones are made up of:-
- A. Amorphous cholesterol dihydrate
- B. Amorphous cholesterol monohydrate
- C. Crystalline cholesterol monohydrate (Correct Answer)
- D. Crystalline cholesterol dihydrate
Explanation: ***Crystalline cholesterol monohydrate*** - **Cholesterol gallstones** primarily consist of **crystalline cholesterol monohydrate**, which forms when the bile becomes supersaturated with cholesterol [1]. - The **crystallization** of cholesterol leads to the formation of visible stones within the gallbladder. *Amorphous cholesterol dihydrate* - This form of cholesterol is not typically found as the primary component of **gallstones**. - **Amorphous** structures lack a defined crystalline lattice and are less stable for forming solid stones. *Amorphous cholesterol monohydrate* - While **cholesterol monohydrate** is the core component, it is in a **crystalline** rather than amorphous state in gallstones [1]. - **Amorphous** forms are generally transient intermediates and do not constitute the bulk of the stones. *Crystalline cholesterol dihydrate* - **Dihydrate** forms of cholesterol are not the main constituent of gallstones; the **monohydrate** form is the predominant type [1]. - The specific hydration state of **cholesterol monohydrate** makes it the primary compound found in the solid, crystalline structure of gallstones [1]. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Liver and Gallbladder, p. 882.
Pediatrics
1 questionsWhich among the following is NOT part of the classic clinical triad of necrotizing enterocolitis?
NEET-PG 2019 - Pediatrics NEET-PG Practice Questions and MCQs
Question 161: Which among the following is NOT part of the classic clinical triad of necrotizing enterocolitis?
- A. Bloody stools
- B. Metabolic acidosis (Correct Answer)
- C. Pneumatosis intestinalis
- D. Abdominal distension
Explanation: ***Metabolic acidosis*** - Metabolic acidosis is **not** part of the classic clinical triad of necrotizing enterocolitis, though it is a common laboratory finding in severe cases. - The **classic triad of NEC** consists of: **abdominal distension**, **bloody stools**, and **pneumatosis intestinalis** on radiography. - Metabolic acidosis occurs as a consequence of intestinal ischemia and sepsis but is not included in the defining triad. *Abdominal distension* - **Abdominal distension** is a cardinal clinical feature and part of the classic triad. - Results from intestinal inflammation, ileus, and gas accumulation. *Bloody stools* - **Bloody stools** (grossly bloody or occult blood positive) are part of the classic triad. - Reflect mucosal injury and intestinal necrosis. *Pneumatosis intestinalis* - **Pneumatosis intestinalis** (intramural gas on abdominal X-ray) is the pathognomonic radiological finding in the classic triad. - Indicates gas-forming bacterial invasion of the damaged intestinal wall.
Pharmacology
1 questionsMannitol is used in the management of:-
NEET-PG 2019 - Pharmacology NEET-PG Practice Questions and MCQs
Question 161: Mannitol is used in the management of:-
- A. Acute renal failure
- B. Pulmonary edema
- C. Congestive cardiac failure
- D. Acute angle-closure glaucoma (Correct Answer)
Explanation: ***Acute angle-closure glaucoma*** - **Mannitol** is an osmotic diuretic [1] used to rapidly reduce **intraocular pressure** in conditions like acute angle-closure glaucoma [2]. - It works by creating an **osmotic gradient** that draws fluid from the vitreous humor into the bloodstream [2]. - This is a well-established **emergency indication** for mannitol [2]. *Acute renal failure* - While mannitol may be used in **prevention** of acute kidney injury (e.g., in rhabdomyolysis, cardiovascular surgery) [2], its use in established acute renal failure is generally **contraindicated** if the patient is **anuric**, as it can exacerbate fluid overload [2]. - It is **not a primary management** for acute renal failure among the given options. *Pulmonary edema* - **Mannitol** is generally **contraindicated** in pulmonary edema because its initial effect is to increase **intravascular volume** [2], which can worsen fluid accumulation in the lungs. - Loop diuretics like **furosemide** are preferred for their rapid onset and profound diuretic effect in pulmonary edema. *Congestive cardiac failure* - **Mannitol** is typically **contraindicated** in congestive cardiac failure as it can cause a **transient increase in plasma volume**, potentially worsening cardiac workload and leading to decompensation [2]. - Diuretics commonly used in heart failure, such as **loop diuretics** (e.g., furosemide) or **thiazide diuretics**, are preferred to reduce fluid overload.
Surgery
1 questionsAll of the following statements are true about Frey's Syndrome except
NEET-PG 2019 - Surgery NEET-PG Practice Questions and MCQs
Question 161: All of the following statements are true about Frey's Syndrome except
- A. Less chances with enucleation than parotidectomy
- B. Gustatory sweating
- C. Aberrant misdirection of parasympathetic fibers of auriculotemporal nerve
- D. Sympathetic nerve involvement is the primary cause (Correct Answer)
Explanation: ***Sympathetic nerve involvement is the primary cause*** - **This is FALSE (Correct answer for EXCEPT question)** - Frey's syndrome is **NOT** caused by sympathetic nerve involvement - The primary cause is **aberrant regeneration of severed PARASYMPATHETIC fibers** of the auriculotemporal nerve - These parasympathetic fibers mistakenly re-innervate sweat glands (which are sympathetically innervated) instead of the parotid gland - This misdirection causes gustatory sweating during meals *Less chances with enucleation than parotidectomy* - **TRUE** - Enucleation is a less extensive procedure compared to complete parotidectomy - Less tissue removal means less nerve disruption and lower risk of auriculotemporal nerve damage - The risk of Frey's syndrome is directly proportional to the extent of parotid tissue removal *Gustatory sweating* - **TRUE** - This is the hallmark symptom of Frey's syndrome - Characterized by sweating on the skin over the parotid region in response to salivary stimuli (smelling, seeing, or eating food) - Results from misdirected parasympathetic fibers stimulating sweat glands instead of salivary tissue *Aberrant misdirection of parasympathetic fibers of auriculotemporal nerve* - **TRUE** - This is the correct pathophysiological mechanism underlying Frey's syndrome - Following injury to the auriculotemporal nerve during parotid surgery, regenerating parasympathetic secretomotor fibers become misdirected - These fibers intended for the parotid gland instead innervate sweat glands in the overlying skin