Neuroanatomy — MCQs

Neuroanatomy Indian Medical PG Practice Questions and MCQs

Question 1101: Which of the following complement components is chemotactic?

A. C3a
B. C5a (Correct Answer)
C. Both
D. C3b

Explanation: The complement system is a crucial part of the innate immune response, involving a cascade of proteins that lead to pathogen clearance [1]. The correct answer is **C5a** because it is the most potent **chemoattractant** (chemotactic factor) of the complement system. * **C5a (Correct):** Known as a "complete" anaphylatoxin, C5a functions as a powerful chemotactic agent for neutrophils, monocytes, eosinophils, and basophils. It recruits these inflammatory cells to the site of infection and also increases vascular permeability. * **C3a (Incorrect):** While C3a is an **anaphylatoxin** (triggers histamine release from mast cells), it has negligible chemotactic activity compared to C5a. Its primary role is inducing local inflammation and vasodilation. * **C3b (Incorrect):** C3b acts primarily as an **opsonin**. It coats the surface of pathogens, making them "tasty" for phagocytes (macrophages and neutrophils) which possess C3b receptors. It also helps in the formation of C5 convertase. **High-Yield Clinical Pearls for NEET-PG:** 1. **Potency Order:** For chemotaxis, C5a is significantly more potent than C3a. 2. **Opsonization:** Remember the mnemonic **"C3b binds bacteria"** (Opsonization). 3. **Anaphylatoxins:** C3a, C4a, and C5a (in increasing order of potency: C4a < C3a < C5a). 4. **Membrane Attack Complex (MAC):** Formed by C5b-C9; essential for lysing Gram-negative bacteria like *Neisseria*. 5. **Deficiency:** C3 deficiency is the most severe as it is the central point of all three pathways, leading to recurrent pyogenic infections.

Question 1102: Which of the following is associated with hyperglycemia?

A. Multiple myeloma
B. Ewing's sarcoma
C. Osteosarcoma (Correct Answer)
D. Chondroblastoma

Explanation: **Explanation:** The association between **Osteosarcoma** and **hyperglycemia** (or impaired glucose tolerance) is a classic high-yield association in orthopedic oncology. **Why Osteosarcoma is correct:** Clinical studies and historical data have consistently shown that a significant percentage of patients with Osteosarcoma exhibit **impaired glucose tolerance** or overt hyperglycemia. While the exact pathophysiology remains a subject of research, it is hypothesized to be related to growth hormone axes or metabolic alterations inherent to the tumor’s rapid osteoblastic activity [1]. Additionally, Osteosarcoma is the most common primary malignant bone tumor in children and young adults, often occurring during growth spurts [2]. **Why the other options are incorrect:** * **Multiple Myeloma (A):** This is a plasma cell dyscrasia primarily associated with **hypercalcemia**, renal failure, and anemia (CRAB criteria), but not specifically with hyperglycemia. * **Ewing’s Sarcoma (B):** This is a small round blue cell tumor [3]. Its systemic manifestations usually include fever and elevated ESR (mimicking osteomyelitis), but it lacks a metabolic link to glucose intolerance. * **Chondroblastoma (D):** This is a benign bone tumor typically occurring in the epiphysis [2]. It does not carry systemic metabolic associations like hyperglycemia. **High-Yield Pearls for NEET-PG:** * **Osteosarcoma:** Associated with **Retinoblastoma (RB1)** and **Li-Fraumeni (TP53)** syndromes [1]. Radiologically presents with **Sunray appearance** and **Codman’s triangle** [1]. * **Metabolic Link:** Remember the "Rule of H": **H**yperglycemia is seen in **O**steosarcoma (think "Sugar-Sarcoma"). * **Alkaline Phosphatase (ALP):** Serum ALP is often elevated in Osteosarcoma and serves as a marker for prognosis and treatment response.

Question 1103: Which of the following disorders has been shown to be genetically transmitted by single autosomal dominant genes?

A. Catatonic schizophrenia
B. Phenylketonuria
C. Creutzfeldt-Jakob disease
D. Huntington's disease (Correct Answer)

Explanation: ### Explanation **Correct Answer: D. Huntington's disease** **1. Why Huntington’s Disease is Correct:** Huntington’s disease (HD) is a classic example of a neurodegenerative disorder inherited in an **autosomal dominant** pattern [1]. It is caused by an unstable expansion of **CAG trinucleotide repeats** in the *HTT* gene located on **chromosome 4**. This leads to the production of an abnormal huntingtin protein, which causes selective neuronal death in the **caudate nucleus** and **putamen** (striatum). Clinical hallmarks include chorea, dementia, and psychiatric disturbances [1]. **2. Analysis of Incorrect Options:** * **A. Catatonic Schizophrenia:** Schizophrenia is a complex polygenic disorder with multifactorial inheritance (interaction between multiple genes and environmental factors), not a single-gene autosomal dominant trait. * **B. Phenylketonuria (PKU):** PKU is an inborn error of metabolism inherited in an **autosomal recessive** pattern. It involves a deficiency of the enzyme phenylalanine hydroxylase. * **C. Creutzfeldt-Jakob Disease (CJD):** Most cases of CJD are **sporadic** (85%). While a small percentage (familial CJD) is genetic, the disease itself is primarily classified as a prion disease (transmissible spongiform encephalopathy) rather than a classic single-gene dominant disorder in general medical contexts [2]. **3. High-Yield Clinical Pearls for NEET-PG:** * **Anticipation:** HD shows "anticipation," where the disease severity increases or age of onset decreases in successive generations, especially when inherited from the **father**. * **Neuroanatomy:** On MRI/CT, look for **"boxcar ventricles"** due to atrophy of the caudate nucleus head. * **Biochemical Change:** There is a marked **decrease in GABA and Acetylcholine**, with an increase in Dopamine in the basal ganglia. * **Trinucleotide Repeat Disorders:** Remember the mnemonic "Huntington's, Myotonic Dystrophy, and Friedreich's Ataxia" (though Friedreich's is recessive).

Question 1104: What cells are responsible for myelination in the Central Nervous System (CNS)?

A. Astrocytes
B. Oligodendrocytes (Correct Answer)
C. Ependymal cells
D. Microglia

Explanation: **Explanation:** The correct answer is **B. Oligodendrocytes**. In the Central Nervous System (CNS), myelination is performed by **Oligodendrocytes** [2]. A single oligodendrocyte can extend its processes to myelinate segments of up to 50 different axons [3], [4]. This is in contrast to the Peripheral Nervous System (PNS), where **Schwann cells** are responsible for myelination, with one Schwann cell providing myelin for only a single axonal segment [2], [4]. **Analysis of Incorrect Options:** * **A. Astrocytes:** These are the most numerous glial cells [1]. They form the Blood-Brain Barrier (BBB), provide structural support, and regulate the chemical environment (potassium buffering). * **C. Ependymal Cells:** These ciliated epithelial cells line the ventricles of the brain and the central canal of the spinal cord. They are involved in the production and circulation of Cerebrospinal Fluid (CSF). * **D. Microglia:** These are the resident macrophages of the CNS [1]. Derived from the mesoderm (monocyte-macrophage lineage), they act as the primary immune defense [1]. **High-Yield Clinical Pearls for NEET-PG:** * **Multiple Sclerosis (MS):** An autoimmune demyelinating disease specifically targeting **Oligodendrocytes** (CNS) [4]. * **Guillain-Barré Syndrome (GBS):** An inflammatory demyelinating disease targeting **Schwann cells** (PNS). * **Origin:** Most glial cells (Astrocytes, Oligodendrocytes, Ependyma) are **ectodermal** in origin, whereas Microglia are **mesodermal** [1]. * **Friedreich's Ataxia:** Often involves loss of myelination in the spinal cord tracts.

Question 1105: What is the most common bone fractured when viewing the skull from the norma frontalis perspective?

A. Nasal bone (Correct Answer)
B. Mandible
C. Parietal eminence
D. Orbital bones

Explanation: The **nasal bone** is the most common bone fractured in the human skull, particularly when viewed from the *norma frontalis* (front view) [1]. This is due to its prominent, central position on the face and its relatively thin, fragile structure compared to the surrounding facial bones. It is frequently injured in motor vehicle accidents, sports, and physical altercations. **Analysis of Options:** * **A. Nasal bone (Correct):** Its protrusion makes it the first point of impact in many facial traumas [1]. It is the most common facial fracture and the most common skull fracture overall. * **B. Mandible:** While the mandible is the second most common facial bone fractured, it is a much stronger, denser bone than the nasal bone and requires more significant force to break. * **C. Parietal eminence:** This is a feature of the *norma verticalis* or *lateralis*. While it is a common site for skull vault fractures in head injuries, it is not the most common fracture viewed from the front. * **D. Orbital bones:** Specifically the orbital floor (blow-out fracture), these are common but usually occur secondary to direct trauma to the globe or infraorbital rim, occurring less frequently than nasal fractures. **Clinical Pearls for NEET-PG:** * **Most common facial fracture:** Nasal bone > Mandible > Zygoma. * **Epistaxis:** The most common clinical sign associated with nasal bone fractures due to mucosal tearing. * **Septal Hematoma:** A critical complication to rule out; if left untreated, it can lead to "Saddle Nose" deformity due to ischemic necrosis of the septal cartilage. * **Le Fort Fractures:** Remember these involve the maxilla and are classified based on the lines of weakness in the midface [2].

Question 1106: Which of the following is an example of active diffusion?

A. Glucose transporter
B. Aquaporin
C. Sodium-glucose linked transporter (Correct Answer)
D. All of the above

Explanation: ### Explanation The term **"Active Diffusion"** is often used interchangeably with **Secondary Active Transport**. Unlike simple or facilitated diffusion, which are passive processes, active transport requires energy to move solutes against their concentration gradient. **Why Option C is Correct:** The **Sodium-Glucose Linked Transporter (SGLT)** is a classic example of **Secondary Active Transport (Symport)** [4]. It does not use ATP directly. Instead, it utilizes the energy generated by the sodium concentration gradient (maintained by the Na+/K+ ATPase pump) to "drag" glucose into the cell against its own concentration gradient [5]. Because it relies on an established electrochemical gradient to move molecules, it is categorized as active transport. **Why Other Options are Incorrect:** * **A. Glucose Transporter (GLUT):** These are examples of **Facilitated Diffusion**. They move glucose down its concentration gradient (from high to low) using a carrier protein without requiring energy. * **B. Aquaporins:** These are specialized water channels that facilitate **Osmosis** (a form of passive diffusion) [2]. Water moves through these pores following osmotic gradients without energy expenditure. **NEET-PG High-Yield Pearls:** * **SGLT-1** is primarily located in the **Small Intestine** (for glucose absorption) [3]. * **SGLT-2** is located in the **Proximal Convoluted Tubule (PCT)** of the kidney [4]. This is the target of **Gliflozins** (e.g., Dapagliflozin), a major class of drugs for Type 2 Diabetes. * **GLUT-4** is the only **insulin-dependent** glucose transporter, found in skeletal muscle and adipose tissue. * **Primary Active Transport** examples include the Na+/K+ ATPase, Ca2+ ATPase, and H+/K+ ATPase (Proton pump) [1].

Question 1107: All of the following conditions may predispose to pulmonary embolism except?

A. Protein S deficiency
B. Malignancy
C. Obesity
D. Progesterone therapy (Correct Answer)

Explanation: The risk of venous thromboembolism (VTE) and subsequent pulmonary embolism (PE) is primarily driven by **Virchow’s Triad**: endothelial injury, stasis, and hypercoagulability. **Why Progesterone therapy is the correct answer:** While **Estrogen** is a well-known risk factor for VTE (as it increases clotting factors and decreases Antithrombin III) [1], **Progesterone alone** (progestogen-only therapy) does not significantly increase the risk of thromboembolism. In clinical practice, progestogen-only pills (POPs) or levonorgestrel-releasing IUDs are often the preferred contraceptive methods for patients with a high risk of VTE. **Analysis of Incorrect Options:** * **Protein S deficiency:** Protein S is a natural anticoagulant that acts as a cofactor for Protein C. A deficiency leads to a hypercoagulable state, significantly increasing the risk of deep vein thrombosis (DVT) and PE [1]. * **Malignancy:** Cancers (especially adenocarcinoma) induce a prothrombotic state through the release of tissue factors and mucins (Trousseau’s syndrome), making it a major risk factor for PE. * **Obesity:** Obesity promotes VTE through multiple mechanisms, including chronic low-grade inflammation, increased intra-abdominal pressure leading to venous stasis in the lower limbs, and decreased fibrinolytic activity. **High-Yield Clinical Pearls for NEET-PG:** * **Most common source of PE:** Deep veins of the lower limbs (above the knee), specifically the **iliofemoral veins** [2]. * **Most common inherited hypercoagulable state:** Factor V Leiden mutation (resistance to Protein C) [1]. * **Gold Standard Investigation for PE:** CT Pulmonary Angiography (CTPA). * **ECG Finding:** Most common is sinus tachycardia; most specific is the **S1Q3T3 pattern**.

Question 1108: What is the macrophage of the brain?

A. Schwann cells
B. Oligodendrocytes
C. Astrocytes
D. Microglia (Correct Answer)

Explanation: **Explanation:** The correct answer is **Microglia**. These cells are the resident macrophages of the Central Nervous System (CNS) [1]. Unlike other glial cells, microglia are derived from **mesoderm** (specifically yolk sac macrophages) rather than the neuroectoderm [1]. They act as the primary immune defense, scavenging for plaques, damaged neurons, and infectious agents [1]. When activated, they undergo morphological changes to become phagocytic [2]. **Analysis of Incorrect Options:** * **Schwann cells:** These are the myelinating cells of the **Peripheral Nervous System (PNS)**. One Schwann cell provides a myelin sheath for only a single axon segment [1][2]. * **Oligodendrocytes:** These are the myelinating cells of the **Central Nervous System (CNS)**. Unlike Schwann cells, one oligodendrocyte can myelinate segments of multiple axons (up to 50) [1][2]. * **Astrocytes:** These are the most numerous glial cells. They provide structural support, form the **Blood-Brain Barrier (BBB)**, and regulate the chemical environment. They are not phagocytic in the immune sense. **High-Yield Clinical Pearls for NEET-PG:** * **Origin:** Microglia are the only CNS glial cells of **mesodermal origin** (others are neuroectodermal) [1]. * **HIV Pathology:** Microglia are the primary targets of HIV in the brain; they fuse to form **multinucleated giant cells**, a hallmark of HIV-associated dementia [1]. * **Gitter Cells:** When microglia phagocytose lipids from necrotic brain tissue (e.g., after an infarct), they are called Gitter cells or "compound granular corpuscles." * **Fried Egg Appearance:** This is a classic histological description for Oligodendrocytes on routine staining.

Question 1109: Heterotopic calcification occurs in which of the following conditions?

A. Ankylosing spondylitis (Correct Answer)
B. Reiter's syndrome
C. Forrestier's disease
D. Rheumatic arthritis

Explanation: **Explanation:** **Heterotopic calcification** (or ossification) refers to the abnormal formation of bone or calcium deposits within soft tissue structures where bone does not normally exist, such as ligaments, tendons, and muscles. **1. Why Ankylosing Spondylitis (AS) is correct:** AS is a chronic inflammatory seronegative spondyloarthropathy primarily affecting the sacroiliac joints and the axial skeleton [1]. The hallmark of AS is **enthesitis** (inflammation at the site where ligaments/tendons attach to bone) [1]. This inflammation triggers a healing response characterized by **heterotopic ossification** of the outer fibers of the **annulus fibrosus** and the **interspinal ligaments**. This leads to the formation of **syndesmophytes** (bony bridges), eventually resulting in the classic "Bamboo Spine" appearance on X-ray. **2. Analysis of Incorrect Options:** * **Reiter’s Syndrome (Reactive Arthritis):** While it involves enthesitis, it typically presents with asymmetric peripheral arthritis and "fluffy" periosteal reactions rather than the systematic heterotopic calcification of spinal ligaments seen in AS. * **Forrestier’s Disease (DISH):** This involves Diffuse Idiopathic Skeletal Hyperostosis. While it features massive calcification of the **Anterior Longitudinal Ligament**, it is considered a degenerative/metabolic condition rather than a primary inflammatory heterotopic process like AS. (Note: In some contexts, DISH is a form of calcification, but AS is the classic "textbook" answer for inflammatory heterotopic ossification in NEET-PG). * **Rheumatoid Arthritis:** This is primarily a synovial-based erosive disease. It leads to bone *destruction* and joint laxity (e.g., atlantoaxial subluxation) rather than heterotopic bone formation. **3. High-Yield Clinical Pearls for NEET-PG:** * **HLA-B27 Association:** Strongly positive in AS (>90%) [1]. * **Radiological Signs:** "Bamboo spine," "Dagger sign" (calcification of supraspinous/interspinous ligaments), and "Shiny corner sign" (Romanus lesion). * **Schober’s Test:** Used to clinically assess the restriction of lumbar spine flexion in AS patients. * **Extra-articular manifestation:** Acute anterior uveitis is the most common.

Question 1110: Which of the following cells are NOT present in the cerebellar cortex?

A. Purkinje cells
B. Bipolar cells (Correct Answer)
C. Granule cells
D. Golgi cells

Explanation: The cerebellar cortex is organized into three distinct layers: the **Molecular layer** (outer), the **Purkinje cell layer** (middle), and the **Granular layer** (inner) [1]. ### Why Bipolar Cells is the Correct Answer: **Bipolar cells** are specialized sensory neurons characterized by two processes (one axon and one dendrite) [3]. They are primarily found in the **retina** of the eye, the **olfactory epithelium**, and the **vestibulocochlear nerve** (Spiral and Scarpa’s ganglia) [2]. They are **not** components of the cerebellar architecture. ### Analysis of Incorrect Options: * **Purkinje cells (Option A):** These are the hallmark cells of the cerebellum. Located in the middle layer, they are the only cells that provide **inhibitory output** (via GABA) from the cerebellar cortex to the deep cerebellar nuclei [1]. * **Granule cells (Option C):** Located in the innermost layer, these are the most numerous neurons in the brain. They are the only **excitatory** neurons in the cerebellar cortex and give rise to **parallel fibers** [1]. * **Golgi cells (Option D):** Found in the granular layer, these are inhibitory interneurons that form part of the "cerebellar glomerulus," regulating the input from mossy fibers to granule cells [1]. ### High-Yield Clinical Pearls for NEET-PG: * **Mnemonic for Cerebellar Layers:** **M**-**P**-**G** (Molecular, Purkinje, Granular). * **Cells by Layer:** * *Molecular:* Stellate and Basket cells [1]. * *Purkinje:* Purkinje cell bodies. * *Granular:* Granule cells and Golgi cells. * **Afferent Fibers:** Remember that **Climbing fibers** (from the inferior olivary nucleus) and **Mossy fibers** (from all other sources) provide the main excitatory input to the cerebellum [1]. * **Functional Unit:** The **Purkinje cell** is the functional unit; its destruction leads to classic cerebellar signs like ataxia and hypotonia.

Practice by Chapter

Organization of the Nervous System

Practice Questions

Spinal Cord Anatomy

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Brainstem Anatomy

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Cerebellum

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Diencephalon

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Cerebral Cortex

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Basal Ganglia

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Limbic System

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Cranial Nerves

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Autonomic Nervous System

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Neural Pathways and Tracts

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Neurovascular Anatomy

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