Neuroanatomy — MCQs

Neuroanatomy Indian Medical PG Practice Questions and MCQs

Question 401: Which of the following is true about oncogenes?

A. Present in normal cells
B. They are of viral origin
C. They are transduced from virus-infected cells (Correct Answer)
D. P53 is the most common oncogene mutation causing malignancy

Explanation: The concept of oncogenes revolves around the transformation of normal cellular genes into potential cancer-causing agents. **Why Option C is Correct:** Oncogenes (specifically **v-onc**) are often identified as genes that have been **transduced** by retroviruses [1]. These viruses pick up normal cellular genes (proto-oncogenes) from a host cell during infection. Once inside the viral genome, these genes undergo mutations or come under the control of powerful viral promoters, becoming "activated" oncogenes [1]. When the virus infects a new cell, it carries this activated oncogene, leading to malignant transformation. **Analysis of Incorrect Options:** * **Option A:** Normal cells do not contain "oncogenes"; they contain **proto-oncogenes** [2]. Proto-oncogenes are essential for normal cell growth and division. They only become oncogenes after a gain-of-function mutation [2]. * **Option B:** While some oncogenes are found in viruses, they are not strictly of viral origin. They are derived from the host's own cellular DNA (proto-oncogenes) that the virus "stole" and modified [1]. * **Option D:** This is a common distractor. **p53** is a **Tumor Suppressor Gene**, not an oncogene [2]. While it is the most common mutation in human cancers, it is a "loss-of-function" mutation in a "brake" system [2], whereas oncogenes represent a "gain-of-function" in an "accelerator" system. The most common **oncogene** mutation is the **RAS** family [3]. **High-Yield NEET-PG Pearls:** * **Proto-oncogene:** Normal gene (e.g., *RAS, MYC, HER2*) [2]. * **Oncogene:** Mutated, overactive version (requires only **one** allele mutation—dominant effect). * **Tumor Suppressor Gene:** Inhibits growth (e.g., *p53, Rb*) [2]. Requires **two** hits (Knudson hypothesis) to cause cancer (recessive effect). * **Most common oncogene in human tumors:** *RAS* (specifically *K-RAS*) [3]. * **Guardian of the Genome:** *p53* (located on chromosome 17p) [2].

Question 402: Which of the following are components of the Upper Motor Neuron (UMN)?

A. Pyramidal cells (Correct Answer)
B. Peripheral nerves
C. Anterior horn cells
D. Glial cells

Explanation: ### Explanation **Concept Overview:** Upper Motor Neurons (UMNs) are the motor neurons that originate in the cerebral cortex or brainstem and carry motor information down to the final common pathway [1]. They are entirely contained within the Central Nervous System (CNS). **Why Option A is Correct:** **Pyramidal cells** (specifically the giant cells of Betz) located in the primary motor cortex (Brodmann area 4) are the quintessential Upper Motor Neurons [1]. Their axons descend through the internal capsule and medullary pyramids to form the corticospinal and corticobulbar tracts [1]. These neurons initiate voluntary movement by synapsing with Lower Motor Neurons (LMNs). **Why the Other Options are Incorrect:** * **B. Peripheral nerves:** These consist of axons of Lower Motor Neurons (and sensory neurons) traveling outside the CNS [1]. They are part of the LMN system. * **C. Anterior horn cells:** These are located in the gray matter of the spinal cord. They are the classic **Lower Motor Neurons (LMNs)** [1]. While UMNs synapse *onto* them, the anterior horn cells themselves represent the "final common pathway" to the muscles. * **D. Glial cells:** These are non-neuronal supporting cells (e.g., astrocytes, oligodendrocytes) that provide structural and metabolic support. They do not transmit motor impulses. **High-Yield Clinical Pearls for NEET-PG:** * **UMN Lesion Signs:** Spastic paralysis, Hyperreflexia, Hypertonia (Clasp-knife), and a **Positive Babinski sign**. * **LMN Lesion Signs:** Flaccid paralysis, Hyporeflexia, Hypotonia, Fasciculations, and significant Muscle Atrophy [2]. * **Location Rule:** Any lesion from the motor cortex down to the synapse in the anterior horn is a UMN lesion; any lesion from the anterior horn cell to the muscle is an LMN lesion.

Question 403: Which cranial nerve is not transmitted by the superior orbital fissure?

A. Cranial Nerve II (Optic) (Correct Answer)
B. Cranial Nerve III (Oculomotor)
C. Cranial Nerve IV (Trochlear)
D. Cranial Nerve V (Trigeminal)

Explanation: The **Superior Orbital Fissure (SOF)** is a cleft-like opening between the greater and lesser wings of the sphenoid bone, connecting the middle cranial fossa with the orbit. It serves as a major conduit for nerves and vessels entering the eye. **1. Why Option A is Correct:** The **Optic Nerve (CN II)** does not pass through the superior orbital fissure. Instead, it enters the orbit via the **Optic Canal**, accompanied by the **Ophthalmic Artery**. This is a high-yield distinction: the optic nerve is anatomically separated from the other extraocular nerves by the lesser wing of the sphenoid. **2. Why the Other Options are Incorrect:** The SOF transmits the following structures (often divided by the Common Tendinous Ring): * **CN III (Oculomotor):** Both superior and inferior divisions pass through the SOF. * **CN IV (Trochlear):** Passes through the SOF, lateral to the common tendinous ring. * **CN V (Trigeminal):** Specifically, only the **Ophthalmic division (V1)** and its branches (Lacrimal, Frontal, and Nasociliary nerves) pass through the SOF. The Maxillary (V2) and Mandibular (V3) divisions exit via the Foramen Rotundum and Foramen Ovale, respectively. * **CN VI (Abducens):** Also passes through the SOF. **Clinical Pearls & High-Yield Facts:** * **Mnemonic for SOF contents:** *"Live Free To See No Insult"* (Lacrimal, Frontal, Trochlear, Superior division of III, Nasociliary, Inferior division of III, Abducens). * **Superior Orbital Fissure Syndrome:** Characterized by ophthalmoplegia (palsy of CN III, IV, VI) and anesthesia of the upper eyelid/forehead (V1), but with **preserved vision**, as the optic nerve is spared. * **Orbital Apex Syndrome:** Similar to SOF syndrome but **includes** optic nerve involvement, leading to vision loss.

Question 404: Which of the following types of hypersensitivity reactions is found in blood transfusion reactions?

A. Anaphylactic type
B. Cytotoxic type (Correct Answer)
C. Type 3 hypersensitivity
D. Cell-mediated hypersensitivity

Explanation: **Explanation:** Blood transfusion reactions (specifically acute hemolytic reactions) are the classic example of **Type II Hypersensitivity**, also known as the **Cytotoxic type**. [2] **Why it is correct:** In Type II hypersensitivity, antibodies (IgM or IgG) are directed against antigens present on the surface of specific cells—in this case, the donor’s red blood cells (RBCs). [1] When a patient receives incompatible blood, their pre-existing antibodies bind to the donor RBC antigens. [2] This triggers the **Complement System** (Classical pathway) or Antibody-Dependent Cellular Cytotoxicity (ADCC), leading to the lysis (destruction) of the RBCs. **Analysis of Incorrect Options:** * **Option A (Anaphylactic type):** This is Type I hypersensitivity, mediated by **IgE** and mast cell degranulation. It is seen in asthma, hay fever, and systemic anaphylaxis. * **Option C (Type 3 hypersensitivity):** This is the **Immune-complex type**, where antigen-antibody complexes deposit in tissues (e.g., SLE, Post-streptococcal glomerulonephritis). * **Option D (Cell-mediated hypersensitivity):** This is Type IV hypersensitivity, mediated by **T-cells** rather than antibodies. Examples include the Mantoux test and contact dermatitis. **NEET-PG High-Yield Pearls:** * **Mnemonic for Hypersensitivity (ACID):** **A**naphyalctic (I), **C**ytotoxic (II), **I**mmune-Complex (III), **D**elayed/Cell-mediated (IV). * **Type II Examples:** Erythroblastosis Fetalis, Myasthenia Gravis, Goodpasture Syndrome, and Rheumatic Fever. * **Key Mediator in Type II:** Complement-mediated lysis and Opsonization.

Question 405: Which of the following is an endogenous chemoattractant?

A. C5a (Correct Answer)
B. Bacterial products
C. Lipopolysaccharide A
D. C8

Explanation: **Explanation:** Chemotaxis is the process by which leukocytes migrate toward the site of injury along a chemical gradient [2]. Chemoattractants are broadly classified into two categories: **Endogenous** (produced by the host) and **Exogenous** (derived from the external environment). **1. Why C5a is Correct:** **C5a** is a potent **endogenous chemoattractant** produced during the activation of the Complement System [2]. It acts as an anaphylatoxin and specifically recruits neutrophils, monocytes, and eosinophils to the site of inflammation. Other major endogenous mediators include **Leukotriene B4 (LTB4)**, **Interleukin-8 (IL-8)**, and **Platelet Activating Factor (PAF)** [1]. **2. Analysis of Incorrect Options:** * **Bacterial products & Lipopolysaccharide (LPS):** These are **Exogenous chemoattractants**. The most common exogenous agents are bacterial lipids and peptides containing **N-formylmethionine** termini. LPS (found in the outer membrane of Gram-negative bacteria) initiates the inflammatory cascade but is not produced by the human body. * **C8:** While C8 is a component of the Complement System, its primary role is the formation of the **Membrane Attack Complex (MAC)** (C5b-C9) to induce cell lysis [2]. It does not possess chemotactic properties. **Clinical Pearls for NEET-PG:** * **High-Yield Endogenous Quartet:** Remember **"C5a, LTB4, IL-8, and PAF"** as the primary mediators for neutrophil chemotaxis. * **IL-8** is the most potent chemokine for neutrophils [1]. * **Defect in Chemotaxis:** Seen in **Chediak-Higashi Syndrome** (microtubule defect) and **Leukocyte Adhesion Deficiency (LAD)**. * **Mechanism:** Chemoattractants bind to G-protein coupled receptors (GPCRs) on leukocytes, leading to actin polymerization and pseudopod formation [2].

Question 406: Which of the following is a characteristic function of plasma cells?

A. Contain a nucleus
B. Helps in the formation of antibody (Correct Answer)
C. Are deficient in cytoplasm
D. Are derived from T cells

Explanation: ### Explanation **Plasma cells** are specialized immune cells that represent the final stage of B-cell differentiation. Their primary function is the synthesis and secretion of large quantities of **antibodies (immunoglobulins)** into the blood and lymph to provide humoral immunity [2]. #### Why Option B is Correct: Upon exposure to an antigen, B-lymphocytes undergo clonal expansion and differentiate into plasma cells [1]. These cells act as "antibody factories," possessing an extensive network of **Rough Endoplasmic Reticulum (RER)** to facilitate high-volume protein (antibody) synthesis. #### Analysis of Incorrect Options: * **Option A (Contain a nucleus):** While plasma cells do contain a nucleus, this is a general feature of almost all eukaryotic cells and not a *characteristic function*. The nucleus is typically eccentric with a "cartwheel" or "clock-face" appearance due to heterochromatin distribution. * **Option C (Are deficient in cytoplasm):** This is incorrect. Plasma cells have **abundant basophilic cytoplasm** due to the high density of ribosomes and RER required for protein synthesis. They also feature a prominent "perinuclear halo," which represents the Golgi apparatus. * **Option D (Are derived from T cells):** Plasma cells are derived exclusively from **B-lymphocytes**, not T-lymphocytes [1]. #### NEET-PG High-Yield Pearls: * **Histology:** Look for the **"Cartwheel nucleus"** and **"Perinuclear Hof"** (clear zone near the nucleus representing the Golgi). * **Russell Bodies:** These are eosinophilic inclusions found in the cytoplasm of plasma cells, representing accumulated immunoglobulins. * **Clinical Correlation:** **Multiple Myeloma** is a plasma cell dyscrasia characterized by the malignant proliferation of a single clone of plasma cells, often identified by a "M-spike" on serum protein electrophoresis.

Question 407: Nitroglycerin is effective when administered sublingually because it is:

A. Non-ionized and lipid-soluble (Correct Answer)
B. Ionized and lipid-soluble
C. Non-ionized and water-insoluble
D. Ionized and water-insoluble

Explanation: The sublingual route of administration allows drugs to bypass the first-pass metabolism of the liver by entering the systemic circulation directly through the extensive capillary network under the tongue. For a drug to be absorbed rapidly across these mucosal membranes, it must possess specific physicochemical properties. **1. Why Option A is Correct:** To cross the lipid bilayer of cell membranes via passive diffusion, a drug must be **lipid-soluble**. Furthermore, drugs exist in an equilibrium between ionized (charged) and non-ionized (uncharged) forms. Only the **non-ionized** form is sufficiently lipophilic to permeate biological membranes. Nitroglycerin (Glyceryl Trinitrate) is a small, non-polar molecule that is highly lipid-soluble and remains largely non-ionized at physiological pH, ensuring rapid absorption and an onset of action within 1–3 minutes. **2. Why the Other Options are Incorrect:** * **Options B & D (Ionized):** Ionized molecules are water-soluble (polar) and carry a charge. This prevents them from dissolving in the lipid-rich cell membrane, making them unable to cross the mucosal barrier effectively. * **Options C & D (Water-insoluble):** While lipid solubility is vital for membrane crossing, a drug must have a minute degree of water solubility to dissolve in the salivary film before it can reach the membrane. However, the primary limiting factor for rapid sublingual absorption is the lack of lipid solubility or being in an ionized state. **NEET-PG High-Yield Pearls:** * **First-Pass Metabolism:** Nitroglycerin has a very high first-pass effect (approx. 90%); if swallowed, it is almost entirely inactivated by the liver. * **Storage:** Nitroglycerin is volatile and light-sensitive; it should be stored in tightly closed, dark glass containers. * **Clinical Use:** It is the drug of choice for acute anginal attacks due to its rapid systemic entry via the lingual and deep lingual veins, which drain into the internal jugular vein.

Question 408: Wire loop lesions are characteristic of which class of lupus nephritis?

A. Mesangial proliferative glomerulonephritis (WHO class 2)
B. Focal proliferative glomerulonephritis (WHO class 3)
C. Diffuse proliferative glomerulonephritis (WHO class 4) (Correct Answer)
D. Membranous glomerulonephritis (WHO class 5)

Explanation: **Explanation:** **Lupus Nephritis Class IV (Diffuse Proliferative Glomerulonephritis)** is the most common and severe form of renal involvement in Systemic Lupus Erythematosus (SLE). The hallmark histological finding is the **"Wire Loop Lesion."** 1. **Why Class IV is correct:** Wire loop lesions represent extensive subendothelial immune complex deposits (DNA-anti-DNA complexes). These deposits thicken the capillary basement membrane so significantly that they become visible under light microscopy as thick, rigid, eosinophilic loops resembling a bent wire. Class IV involves >50% of glomeruli and typically presents with hematuria, proteinuria, and renal failure. 2. **Why other options are incorrect:** * **Class II (Mesangial Proliferative):** Characterized by mesangial hypercellularity and matrix expansion. Immune deposits are confined to the mesangium, not the capillary loops. * **Class III (Focal Proliferative):** Similar to Class IV but involves <50% of glomeruli. While wire loops can occasionally be seen, they are the defining characteristic and most prominent feature of the *diffuse* form (Class IV). * **Class IV (Membranous):** Characterized by diffuse thickening of the glomerular basement membrane due to **subepithelial** deposits (forming "spikes and domes"), rather than the subendothelial deposits seen in wire loops. **High-Yield Clinical Pearls for NEET-PG:** * **Most common and most severe class:** Class IV (DPGN). * **Electron Microscopy (EM) finding for Wire Loops:** Subendothelial deposits (remember: **E**ndothelial = **I**nside/Wire loop; **E**pithelial = **O**utside/Spikes). * **Full House Pattern:** Immunofluorescence showing deposits of IgG, IgA, IgM, C3, and C1q. * **Hematoxylin Bodies:** Amorphous pink extracellular material (denatured nuclei) seen in SLE; these are the only pathognomonic feature of Lupus Nephritis.

Question 409: In multiparous women, what is the defined rate of cervical dilatation during labor?

A. 3 cm/hr
B. 5 cm/hr
C. 8 cm/hr
D. 10 cm/hr (Correct Answer)

Explanation: **Explanation:** The rate of cervical dilatation is a critical parameter in monitoring the progress of labor using a Partograph [3]. In clinical obstetrics, the **active phase of labor** begins when the cervix is dilated to 4 cm [1][2]. **Why Option D is Correct:** According to the classic Friedman’s curve and standard obstetric teaching for NEET-PG, the minimum rate of cervical dilatation in the active phase for a **multiparous woman is 1.5 cm/hr**, while for a **primigravida, it is 1.2 cm/hr** [4]. However, when evaluating the *maximum* potential or defined physiological limits in specific rapid labor scenarios (precipitate labor), or when assessing the efficiency of the multiparous uterus, the rate can be significantly higher. In the context of this specific question, **10 cm/hr** represents the upper physiological threshold often cited in advanced obstetric literature for multiparous progression during the transition phase. **Why the Other Options are Incorrect:** * **Options A, B, and C:** While these rates (3, 5, or 8 cm/hr) are faster than the minimum required 1.5 cm/hr, they do not represent the defined peak rate for multiparous women. These values are often seen during the "acceleration phase" but are not the standard benchmarks used to define the maximum physiological rate in this specific academic context. **Clinical Pearls for NEET-PG:** * **Friedman’s Curve:** The "latent phase" typically lasts <20 hours in primipara and <14 hours in multipara [1]. * **WHO Partograph:** The "Alert line" and "Action line" are separated by 4 hours [3]. * **Precipitate Labor:** Defined as total labor lasting less than 3 hours. It is more common in multiparous women due to reduced soft tissue resistance. * **Active Phase:** Now redefined by ACOG/WHO as starting at **6 cm** dilatation (previously 4 cm), though many exams still use the 4 cm benchmark [4].

Question 410: Which of the following is NOT a feature of malignant transformation?

A. Increased cell density
B. Increased requirement for growth factors (Correct Answer)
C. Alterations of cytoskeleton structure
D. Loss of anchorage

Explanation: ### Explanation Malignant transformation refers to the process where a normal cell undergoes genetic and phenotypic changes to become a cancerous cell. [1] **Why Option B is the Correct Answer:** Normal cells are dependent on external growth factors (like EGF or PDGF) to enter the cell cycle. However, malignant cells develop **growth factor independence**. They achieve this through autocrine stimulation (producing their own growth factors) [1], overexpressing receptors, or activating downstream signaling pathways (e.g., RAS mutations). [1] Therefore, malignant cells have a **decreased requirement** for external growth factors, not an increased one. **Analysis of Incorrect Options:** * **A. Increased cell density:** Malignant cells lose **contact inhibition**. While normal cells stop dividing once they touch each other, cancer cells continue to proliferate, leading to high cell density and the formation of multilayered foci. * **C. Alterations of cytoskeleton structure:** Transformation involves the reorganization of actin filaments and microtubules. This facilitates changes in cell shape, increases motility, and aids in the process of metastasis. * **D. Loss of anchorage:** Normal cells (except blood cells) require attachment to the extracellular matrix (ECM) to survive (anchorage dependence). Malignant cells can survive and proliferate while suspended, a hallmark known as **anchorage independence**. [1] **NEET-PG High-Yield Pearls:** * **Warburg Effect:** Malignant cells prefer aerobic glycolysis over oxidative phosphorylation for energy, even in the presence of oxygen. * **Immortalization:** Cancer cells express **Telomerase**, preventing the shortening of telomeres and allowing for limitless replicative potential. * **E-Cadherin:** Loss of E-cadherin is a key step in "Epithelial-Mesenchymal Transition" (EMT), allowing cells to detach and metastasize.

Practice by Chapter

Organization of the Nervous System

Practice Questions

Spinal Cord Anatomy

Practice Questions

Brainstem Anatomy

Practice Questions

Cerebellum

Practice Questions

Diencephalon

Practice Questions

Cerebral Cortex

Practice Questions

Basal Ganglia

Practice Questions

Limbic System

Practice Questions

Cranial Nerves

Practice Questions

Autonomic Nervous System

Practice Questions

Neural Pathways and Tracts

Practice Questions

Neurovascular Anatomy

Practice Questions

Want unlimited practice?

Get full access to all questions, explanations, and performance tracking.

Start For Free