Anatomy
1 questionsWhich of the following is a cerebellar nucleus?
NEET-PG 2013 - Anatomy NEET-PG Practice Questions and MCQs
Question 231: Which of the following is a cerebellar nucleus?
- A. Putamen
- B. Caudate nucleus
- C. Subthalamic nucleus
- D. Fastigial nucleus (Correct Answer)
Explanation: ***Fastigial nucleus*** - The **fastigial nucleus** is one of the four principal deep cerebellar nuclei, involved in regulating **balance** and **posture** [2]. - The deep cerebellar nuclei are crucial for the cerebellum's output, relaying processed information to other brain regions [2]. *Caudate nucleus* - The **caudate nucleus** is part of the **basal ganglia**, a group of subcortical nuclei in the forebrain [1]. - It plays a significant role in **motor control**, learning, memory, and reward processing. *Subthalamic nucleus* - The **subthalamic nucleus** is a small nucleus located in the **diencephalon**, below the thalamus and above the substantia nigra [1]. - It is also part of the **basal ganglia system** and is critical for modulating motor control [1]. *Putamen* - The **putamen** is another structure belonging to the **basal ganglia**, located in the forebrain [1]. - It is primarily involved in regulating various types of **motor behavior** and learning.
Biochemistry
1 questionsWhat is the process of Hofmann elimination in organic chemistry?
NEET-PG 2013 - Biochemistry NEET-PG Practice Questions and MCQs
Question 231: What is the process of Hofmann elimination in organic chemistry?
- A. E1 elimination reaction favoring tertiary substrates
- B. E2 elimination reaction producing the least substituted alkene (Correct Answer)
- C. SN1 substitution reaction with carbocation intermediate
- D. SN2 substitution reaction with inversion of configuration
Explanation: ***E2 elimination reaction producing the least substituted alkene*** - **Hofmann elimination** is a type of **E2 elimination** reaction where a **quaternary ammonium salt** is heated in the presence of a strong base. - Unlike most E2 reactions which follow **Zaitsev's rule** (producing the most substituted alkene), Hofmann elimination follows the **Hofmann rule**, leading to the formation of the **least substituted (least stable) alkene**. *SN1 substitution reaction with carbocation intermediate* - **SN1 reactions** involve the formation of a **carbocation intermediate** and are typically substitution reactions, not elimination. - Hofmann elimination is an elimination reaction and does not proceed through a carbocation intermediate. *E1 elimination reaction favoring tertiary substrates* - **E1 reactions** are a two-step process involving a **carbocation intermediate** and generally favor **tertiary substrates** and produce the **Zaitsev product**. - Hofmann elimination is a concerted, one-step E2 mechanism and does not involve carbocations. *SN2 substitution reaction with inversion of configuration* - **SN2 reactions** are **bimolecular nucleophilic substitution** reactions that occur in a single step with **inversion of configuration** at the carbon center. - Hofmann elimination is an elimination process resulting in an alkene, not a substitution product, and does not involve inversion of configuration at a stereocenter.
Pathology
3 questionsMALT lymphoma is positive for which of the following markers?
What is the typical bone marrow finding in myelofibrosis?
Localized Langerhans cell histiocytosis affecting head and neck is?
NEET-PG 2013 - Pathology NEET-PG Practice Questions and MCQs
Question 231: MALT lymphoma is positive for which of the following markers?
- A. CD20 (Correct Answer)
- B. CD19
- C. CD43
- D. CD5
Explanation: ***CD20*** - MALT lymphoma is a type of **B-cell non-Hodgkin lymphoma**, and CD20 is a **pan B-cell marker consistently expressed** in MALT lymphomas. - CD20 positivity is **crucial for diagnosis** and is the **primary therapeutic target** for anti-CD20 monoclonal antibody therapy (Rituximab). - In diagnostic practice, **CD20 is the most important B-cell marker** for identifying MALT lymphoma and guiding treatment decisions. *CD19* - CD19 is also a **pan B-cell marker** and is **typically positive in MALT lymphoma** along with CD20. - However, in the context of this question, **CD20 is the preferred answer** because it is the **standard diagnostic marker emphasized in clinical practice** and the **primary therapeutic target**. - Both markers are positive, but CD20 has greater **clinical and therapeutic significance** in MALT lymphoma management. *CD43* - CD43 is primarily a **T-cell and myeloid marker**, but can show **aberrant expression in 40-50% of MALT lymphomas**. - While it may be positive in some cases, it is **not a defining B-cell lineage marker** and is not used as a primary diagnostic criterion for MALT lymphoma. - Its variable expression makes it **less reliable** than consistent B-cell markers like CD20. *CD5* - CD5 is typically associated with **T-cells** and certain B-cell lymphomas, particularly **chronic lymphocytic leukemia/small lymphocytic lymphoma (CLL/SLL)** and **mantle cell lymphoma**. - **MALT lymphoma is characteristically CD5-negative**, which is an important feature for **differentiating it from CD5+ B-cell lymphomas**.
Question 232: What is the typical bone marrow finding in myelofibrosis?
- A. Megaloblastic cells
- B. Microcytic cells
- C. Thrombocytosis
- D. Dry tap (hypocellular) (Correct Answer)
Explanation: ***Dry tap (hypocellular)*** - In myelofibrosis, the bone marrow is often **hypocellular** due to fibrosis [1][2], leading to a **dry tap** during aspiration. - The presence of **reticulin** and collagen deposition replaces normal hematopoietic cells [2], resulting in ineffective hematopoiesis. *Thrombocytosis* - Myelofibrosis typically leads to **thrombocytopenia**, not thrombocytosis, due to ineffective megakaryopoiesis and splenic sequestration. - Though elevated platelets can occur, they are generally a **secondary response** to the disease and not a hallmark finding. *Megaloblastic cells* - Megaloblastic changes are associated with **vitamin B12** or **folate deficiencies**, which do not occur in myelofibrosis. - In myelofibrosis, the predominant issue is **marrow fibrosis** [1][2], which does not lead to megaloblastosis. *Microcytic cells* - Microcytic cells are commonly linked to **iron deficiency anemia**, not myelofibrosis. - Myelofibrosis typically results in **variable red cell morphology** [1], but microcytic anemia is not a primary characteristic. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Diseases of White Blood Cells, Lymph Nodes, Spleen, and Thymus, pp. 628-629. [2] Cross SS. Underwood's Pathology: A Clinical Approach. 6th ed. Common Clinical Problems From Blood And Bone Marrow Disease, pp. 615-616.
Question 233: Localized Langerhans cell histiocytosis affecting head and neck is?
- A. Eosinophilic granuloma (Correct Answer)
- B. Letterer-siwe disease
- C. Pulmonary Langerhans cell histiocytosis
- D. Hand-Schuller-Christian disease
Explanation: ***Eosinophilic granuloma*** - This is a localized form of **Langerhans cell histiocytosis** that typically presents in the head and neck region, often affecting areas like the skull and mandible [1]. - Characterized by **bone lesions** and may present with **pain or swelling** in the affected area, making it a prominent form in children and young adults. *Pulmonary langerhans cell histiocytosis* - Primarily affects the **lungs** and is associated with **cough, dyspnea**, and pulmonary nodules, not the head and neck region. - Occurs predominantly in **smokers** and involves interstitial lung disease patterns on imaging studies. *Hand-schuller-christian disease* - This condition is a systemic form of Langerhans cell histiocytosis that affects multiple systems rather than being localized, commonly presenting with **diabetes insipidus** and bone lesions. - It is often associated with **exophthalmos** and may involve lymphadenopathy, affecting older children and adults, not localized head and neck involvement. *Letterer-siwe disease* - This represents the acute, disseminated form of Langerhans cell histiocytosis, affecting infants, and is marked by systemic symptoms like **fever**, **rash**, and **hepatosplenomegaly** [1]. - Typically presents with serious manifestations and not specifically localized in the **head and neck area** as seen in eosinophilic granuloma. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Diseases of White Blood Cells, Lymph Nodes, Spleen, and Thymus, p. 630.
Pharmacology
2 questionsWhich of the following is classified as a Type E adverse reaction?
Muscarinic cholinergic receptors are seen at all sites, except?
NEET-PG 2013 - Pharmacology NEET-PG Practice Questions and MCQs
Question 231: Which of the following is classified as a Type E adverse reaction?
- A. Toxicity
- B. Augmented effect
- C. Teratogenesis
- D. Rebound effect due to drug withdrawal (Correct Answer)
Explanation: ***Rebound effect due to drug withdrawal*** - Type E adverse reactions are related to **end-of-treatment effects**, specifically withdrawal phenomena. - The **rebound effect** after drug cessation, such as worsened angina after stopping beta-blockers, is a classic example of a Type E reaction. *Toxicity* - This is a general term for adverse effects from excessive drug doses and is **not a specific type** in the ABCDEF classification. - Dose-dependent toxic effects typically align with **Type A** (augmented) reactions, which are predictable and related to the drug's pharmacology. *Augmented effect* - An **augmented effect** is classified as a Type A adverse drug reaction, meaning it is **dose-dependent**, predictable from the drug's known pharmacology, and common. - Examples include bleeding with anticoagulants or hypotension with antihypertensives. *Teratogenesis* - **Teratogenesis** refers to drug-induced fetal malformations and is categorized as a **Type D** (delayed) adverse drug reaction. - These effects are often severe, occur after prolonged exposure, and are rare.
Question 232: Muscarinic cholinergic receptors are seen at all sites, except?
- A. Stomach
- B. CNS
- C. Glands
- D. Neuromuscular junction (Correct Answer)
Explanation: ***Neuromuscular junction*** - The **neuromuscular junction** primarily contains **nicotinic cholinergic receptors**, not muscarinic receptors. - Activation of these nicotinic receptors by acetylcholine causes muscle contraction. *Stomach* - The stomach contains **muscarinic M3 receptors** which mediate gastric acid secretion and smooth muscle contraction. - Activation by acetylcholine via the vagus nerve promotes digestion. *CNS* - The **central nervous system** has various subtypes of **muscarinic receptors (M1-M5)** distributed throughout, playing roles in learning, memory, and motor control. - These receptors modulate neuronal excitability and neurotransmitter release. *Glands* - Most exocrine glands (e.g., salivary, lacrimal, sweat glands) are richly supplied with **muscarinic receptors**, primarily **M3**. - Activation leads to increased glandular secretion.
Physiology
2 questionsSpinal pathway mainly regulating fine motor activity?
Which of the following substances has the same concentration in cerebrospinal fluid (CSF) and plasma?
NEET-PG 2013 - Physiology NEET-PG Practice Questions and MCQs
Question 231: Spinal pathway mainly regulating fine motor activity?
- A. Lateral corticospinal tract (Correct Answer)
- B. Vestibulospinal tract
- C. Anterior corticospinal tract
- D. Reticulospinal tract
Explanation: ***Lateral corticospinal tract*** - This pathway contains **85-90% of corticospinal fibers** that cross at the medullary pyramids and descend in the **lateral funiculus** of the spinal cord - It is the **primary pathway for fine, precise, voluntary movements** of **distal extremities**, particularly the hands, fingers, feet, and toes - Enables intricate skilled movements like writing, buttoning, and fine manipulation due to direct monosynaptic connections to motor neurons - Damage results in loss of fine motor control and skilled movements *Anterior corticospinal tract* - Contains only **10-15% of corticospinal fibers** that descend uncrossed in the anterior spinal cord - Controls **bilateral movements of axial and proximal muscles** (neck, trunk, shoulders) - Not specialized for fine motor control of distal limbs *Vestibulospinal tract* - Regulates **posture and balance** by modulating extensor muscle tone - Coordinates head position and maintains upright posture - Does not control fine voluntary movements *Reticulospinal tract* - Modulates **muscle tone, posture, and locomotion** - Provides general motor control and autonomic regulation - Not specialized for precise, intricate fine motor movements
Question 232: Which of the following substances has the same concentration in cerebrospinal fluid (CSF) and plasma?
- A. Glucose
- B. Ca
- C. HCO3
- D. Cl (Correct Answer)
Explanation: ***Cl*** - **Chloride ions (Cl-)** have the **closest concentration** between CSF and plasma among the listed options, with a CSF-to-plasma ratio of approximately 1.1-1.15. - CSF chloride is **slightly higher** than plasma chloride (CSF: ~120-130 mEq/L; Plasma: ~100-110 mEq/L) because chloride ions freely cross the **blood-brain barrier** and help maintain **electroneutrality** in CSF due to the low protein content. - The elevated chloride compensates for the absence of negatively charged proteins in CSF, making it the **best answer** among the given options. *Glucose* - **Glucose** concentration in CSF is approximately **60-70%** of plasma glucose concentration (CSF: 50-80 mg/dL; Plasma: 70-110 mg/dL). - Transport across the **blood-brain barrier** occurs via **GLUT1 transporters**, which are tightly regulated to meet brain metabolic demands. *Ca* - **Calcium (Ca2+)** concentration in CSF is **significantly lower** than in plasma (CSF: ~2.1-2.5 mg/dL; Plasma: ~8.5-10.5 mg/dL). - Only the **ionized, unbound fraction** can cross the blood-brain barrier, as protein-bound calcium cannot pass through. *HCO3* - **Bicarbonate (HCO3-)** concentration in CSF is typically **slightly lower** than in plasma (CSF: ~20-25 mEq/L; Plasma: ~22-28 mEq/L). - Active regulation maintains **CSF pH** and CO2 buffering capacity independent of plasma bicarbonate levels.
Psychiatry
1 questionsWhat is the term for the salivation of a dog in response to a bell after it has been conditioned with food?
NEET-PG 2013 - Psychiatry NEET-PG Practice Questions and MCQs
Question 231: What is the term for the salivation of a dog in response to a bell after it has been conditioned with food?
- A. Conditioned reflex (Correct Answer)
- B. Reinforcement
- C. Habituation
- D. Innate reflex
Explanation: ***Conditioned reflex (Conditioned Response)*** - A **conditioned reflex** is a learned response developed through **classical conditioning**, where a previously neutral stimulus becomes associated with an unconditioned stimulus. - In Pavlov's experiment: The **bell (Conditioned Stimulus)** is paired with **food (Unconditioned Stimulus)**, leading the dog to eventually salivate to the bell alone. - The **salivation to the bell** is the **Conditioned Response (CR)** - a learned behavior, not an innate one. *Reinforcement* - **Reinforcement** is a concept from **operant conditioning** (Skinner), not classical conditioning. - It involves strengthening a behavior by providing a consequence (reward or punishment) after the behavior occurs. - This describes a process that increases behavior frequency, not the learned response itself. *Habituation* - **Habituation** is a decrease in response to a repeatedly presented stimulus that proves to be irrelevant. - The organism learns to **ignore** the stimulus over time (e.g., getting used to background noise). - This is the opposite of developing a new learned response. *Innate reflex* - An **innate reflex** is an **unlearned, inborn** automatic response (e.g., salivation directly to food, pupillary reflex, sucking reflex). - The dog's salivation **to food** is innate, but salivation **to the bell** is learned through conditioning.