Neuroanatomy — MCQs

Neuroanatomy Indian Medical PG Practice Questions and MCQs

Question 761: Which of the following is a derivative of the second pharyngeal arch?

A. Malleus
B. Incus
C. Stapes (Correct Answer)
D. None of the above

Explanation: The pharyngeal (branchial) arches are fundamental structures in embryology, each giving rise to specific skeletal, muscular, and neural components. **Correct Answer: C. Stapes** The **second pharyngeal arch (Reichert’s cartilage)** is responsible for the development of several key skeletal structures in the head and neck. These include the **stapes** (except for its footplate, which has a dual origin from the neural crest and otic capsule), the styloid process of the temporal bone, the stylohyoid ligament, and the lesser cornu and upper part of the body of the hyoid bone. **Explanation of Incorrect Options:** * **A & B. Malleus and Incus:** These are derivatives of the **first pharyngeal arch (Meckel’s cartilage)**. The first arch also gives rise to the sphenomandibular ligament and the mandible (via intramembranous ossification around Meckel's cartilage). **High-Yield Clinical Pearls for NEET-PG:** * **Nerve Supply:** The nerve of the second arch is the **Facial Nerve (CN VII)**. Therefore, all muscles derived from this arch (muscles of facial expression, stapedius, stylohyoid, and posterior belly of digastric) are supplied by CN VII. * **The "S" Rule for 2nd Arch:** Remember **S**tapes, **S**tyloid process, **S**tylohyoid ligament, **S**tylohyoid muscle, and **S**even (CN VII). * **Ossicles Origin:** A common exam trap is the origin of the ear ossicles. Remember: Malleus and Incus = 1st Arch; Stapes = 2nd Arch. * **Artery:** The second arch artery regresses but contributes to the formation of the stapedial artery.

Question 762: Which nerve facilitates looking laterally and downward?

A. Abducent nerve
B. Trochlear nerve (Correct Answer)
C. Trigeminal nerve
D. Oculomotor nerve

Explanation: The correct answer is **B. Trochlear nerve**. ### **Explanation** The **Trochlear nerve (CN IV)** innervates the **Superior Oblique (SO)** muscle [1]. To understand its action, one must distinguish between its anatomical pull and its clinical testing position: * **Anatomical Action:** The superior oblique originates posteriorly and passes through a fibrous pulley (the trochlea). Its primary action is **intorsion**, but it also produces **depression** and **abduction** [1]. * **Clinical Testing:** When the eye is adducted (turned medially), the superior oblique acts as a pure depressor [1]. However, the specific movement of looking **"laterally and downward"** (down and out) is the classic functional description of the superior oblique's combined vector of action [1]. ### **Why other options are incorrect:** * **Abducent nerve (CN VI):** Innervates the **Lateral Rectus**. Its sole action is abduction (looking purely laterally), not downward [1]. * **Trigeminal nerve (CN V):** This is a sensory nerve for the face and motor nerve for muscles of mastication; it has no role in extraocular eye movements. * **Oculomotor nerve (CN III):** Innervates the Superior, Inferior, and Medial Recti, and the Inferior Oblique [1]. While the Inferior Rectus depresses the eye, it does so most effectively when the eye is abducted. The Oculomotor nerve is responsible for most other directions, but not the specific "down and out" movement associated with CN IV. ### **NEET-PG High-Yield Pearls:** * **Mnemonic:** **LR6SO4** (Lateral Rectus = CN VI; Superior Oblique = CN IV; all others = CN III). * **Trochlear Nerve Palsy:** Patients present with **vertical diplopia** and a compensatory **head tilt** to the opposite side to minimize double vision [1]. They have particular difficulty walking down stairs. * **Longest & Thinnest:** CN IV is the thinnest cranial nerve and has the longest intracranial course. It is also the only cranial nerve to exit from the **dorsal aspect** of the brainstem.

Question 763: Proprioceptive fibers are not carried by which cranial nerve?

A. Cranial accessory (Correct Answer)
B. Glossopharyngeal
C. Trigeminal
D. Facial

Explanation: Explanation: The correct answer is **Cranial Accessory (Option A)**. Proprioception (position sense) for the muscles of the head and neck is generally carried by the cranial nerves that supply those muscles. However, the **Cranial Accessory nerve (CN XI)** is purely motor. It arises from the nucleus ambiguus, joins the Vagus nerve, and provides motor supply to the muscles of the soft palate and larynx. It does not carry sensory or proprioceptive fibers. **Why the other options are incorrect:** * **Trigeminal (CN V):** This is the primary sensory nerve of the face. Proprioceptive fibers from the muscles of mastication and the TMJ are carried by the Trigeminal nerve, with their cell bodies uniquely located in the **Mesencephalic nucleus** of the midbrain. * **Facial (CN VII):** It carries proprioceptive fibers from the muscles of facial expression. * **Glossopharyngeal (CN IX):** It carries proprioceptive fibers from the stylopharyngeus muscle and general sensation from the posterior third of the tongue and oropharynx. **High-Yield NEET-PG Pearls:** 1. **Mesencephalic Nucleus:** This is the only site in the Central Nervous System (CNS) that contains the cell bodies of primary sensory neurons (unipolar neurons), specifically for proprioception. 2. **Spinal Accessory Nerve:** While the *Cranial* part of CN XI is purely motor, the *Spinal* part (supplying Trapezius and Sternocleidomastoid) receives its proprioceptive fibers via the **Cervical Plexus (C2, C3, C4)**, not the nerve itself. 3. **Extraocular Muscles:** Proprioception from eye muscles is carried by the **Ophthalmic division of the Trigeminal nerve (V1)**, even though the motor supply comes from CN III, IV, and VI.

Question 764: Which of the following is a pneumatic bone?

A. Tibia
B. Frontal bone (Correct Answer)
C. Clavicle
D. Femur

Explanation: **Explanation:** **1. Why Frontal Bone is Correct:** A **pneumatic bone** is defined as a bone that contains air-filled cavities or spaces (sinuses) lined by mucous membranes. These bones are primarily found around the nasal cavity. The **Frontal bone** is a classic example of a pneumatic bone because it houses the **frontal air sinuses**. The primary functions of pneumatization are to reduce the weight of the skull, provide resonance to the voice, and act as a thermal buffer for the brain. **2. Why Other Options are Incorrect:** * **Tibia and Femur (Options A & D):** These are typical **long bones**. While they contain a medullary cavity filled with bone marrow (yellow or red), they do not contain air-filled spaces. * **Clavicle (Option C):** This is a **modified long bone**. It is unique because it is the only long bone that lies horizontally, ossifies in membrane, and lacks a definitive medullary cavity, but it is certainly not pneumatic. **3. Clinical Pearls & High-Yield Facts for NEET-PG:** * **Other Pneumatic Bones:** Maxilla (largest sinus), Ethmoid, Sphenoid, and the Mastoid process of the temporal bone. * **Clinical Significance:** Pneumatic sinuses are prone to infection (**Sinusitis**). The frontal sinus, specifically, drains into the middle meatus of the nose via the infundibulum. * **Development:** Frontal sinuses are usually not radiologically visible until the age of 6–7 years; they are of forensic importance for individual identification (skeletal remains). * **Potential Complication:** Fracture of the frontal bone can lead to **CSF rhinorrhea** if the posterior wall of the sinus and the underlying dura are torn.

Question 765: Wound contraction is mediated by which of the following cells?

A. Epithelial cells
B. Myofibroblasts (Correct Answer)
C. Collagen
D. Elastin

Explanation: **Explanation:** **Wound contraction** is a critical phase of secondary intention healing, aimed at reducing the surface area of the wound. The correct answer is **Myofibroblasts**. 1. **Why Myofibroblasts are correct:** These are specialized fibroblasts that acquire features of smooth muscle cells, specifically the expression of **alpha-smooth muscle actin (α-SMA)**. They appear in the wound around day 3 to 5 [1]. By anchoring themselves to the extracellular matrix and contracting their internal actin-myosin cytoskeleton, they pull the edges of the wound toward the center, significantly decreasing the wound size [1]. Certain growth factors, such as PDGF, are known to stimulate this wound contraction process [1]. 2. **Why other options are incorrect:** * **Epithelial cells:** These are responsible for *re-epithelialization* (covering the wound surface) but do not possess the contractile force required for wound contraction [1]. * **Collagen:** This is a structural protein secreted by fibroblasts. While it provides *tensile strength* to the scar, it is a passive component and does not actively contract. * **Elastin:** This protein provides elasticity and recoil to tissues. It is generally deficient or disorganized in scars, which is why scar tissue is less flexible than original skin. **High-Yield Clinical Pearls for NEET-PG:** * **Secondary Intention:** Wound contraction is a hallmark of healing by secondary intention (large, open wounds) rather than primary intention (sutured wounds). * **Contracture:** Excessive wound contraction can lead to "contractures," commonly seen after severe burn injuries, which can restrict joint mobility. * **Timeline:** Myofibroblasts typically disappear via apoptosis once the wound is closed; their persistence is linked to pathological fibrosis (e.g., hypertrophic scars).

Question 766: The arch of the aorta is derived from all except:

A. Left horn of the yolk sac
B. Left 2nd branchial arch artery (Correct Answer)
C. Left 4th branchial arch artery
D. Left dorsal aorta

Explanation: ### Explanation The development of the aortic arch is a high-yield topic in embryology. The definitive **arch of the aorta** is a composite structure formed from three specific embryonic sources. **1. Why Option B is the Correct Answer:** The **Left 2nd branchial arch artery** does not contribute to the aortic arch. In embryonic development, the 1st and 2nd arch arteries largely disappear. The 2nd arch artery specifically gives rise to the **stapedial and hyoid arteries**. Since it does not participate in the formation of the aorta, it is the "except" in this question. **2. Analysis of Other Options:** * **Left 4th branchial arch artery (Option C):** This is the primary contributor to the segment of the aortic arch located between the left common carotid and the left subclavian arteries. * **Left dorsal aorta (Option D):** The portion of the left dorsal aorta distal to the 4th arch artery forms the distal part of the aortic arch and the descending thoracic aorta. * **Aortic Sac (Left horn):** Though not explicitly listed as "yolk sac" in standard texts (the question likely refers to the **Aortic Sac**), the proximal part of the arch (up to the brachiocephalic trunk) is derived from the **left horn of the aortic sac**. **3. High-Yield NEET-PG Pearls:** * **Right 4th Arch:** Forms the proximal part of the **Right Subclavian Artery**. * **6th Arch (Pulmonary Arch):** The left side forms the **Left Pulmonary Artery** and the **Ductus Arteriosus** (becomes Ligamentum Arteriosum). The right side forms the Right Pulmonary Artery. * **3rd Arch:** Forms the Common Carotid and the proximal part of the Internal Carotid Artery. * **Recurrent Laryngeal Nerve:** The left nerve hooks around the 6th arch derivative (Ductus Arteriosus), while the right nerve hooks around the 4th arch derivative (Right Subclavian) [1].

Question 767: The nucleus pulposus is a remnant of which embryonic structure?

A. Notochord (Correct Answer)
B. Intervertebral disc
C. Spinal cord
D. Spinous process

Explanation: The **nucleus pulposus** is the gelatinous, central core of the intervertebral disc. During embryonic development, the **notochord** serves as the primitive axial skeleton. As the vertebral bodies develop from the sclerotome, the notochord disappears within the vertebrae but persists and expands in the areas between them to form the nucleus pulposus. **Analysis of Options:** * **A. Notochord (Correct):** It is the primary inductor of the neural tube. While most of it degenerates, its remnants specifically form the nucleus pulposus of the intervertebral discs. * **B. Intervertebral disc:** This is the anatomical structure as a whole. The nucleus pulposus is a *part* of the disc, not a remnant of it. The outer part (annulus fibrosus) is derived from the mesenchyme of the sclerotome. * **C. Spinal cord:** The spinal cord develops from the **neural tube**, which is induced by the notochord but is a separate ectodermal structure. * **D. Spinous process:** This is a bony projection of the vertebral arch, which develops from the ossification of the **sclerotome** (mesoderm). **High-Yield Clinical Pearls for NEET-PG:** * **Chordoma:** A rare, slow-growing malignant tumor that arises from persistent remnants of the notochord. It most commonly occurs at the **clivus** (base of the skull) or the **sacrococcygeal region**. * **Disc Herniation:** Usually occurs posterolaterally because the posterior longitudinal ligament is narrow [1]. The nucleus pulposus protrudes through a tear in the annulus fibrosus, often compressing spinal nerve roots [1]. * **Composition:** The nucleus pulposus is rich in Type II collagen and hyaluronic acid, providing shock absorption.

Question 768: All of the following drugs cause hemolysis in patients with G-6 PD deficiency except?

A. Primaquine
B. Chloroquine
C. Quinine
D. Pyrimethamine (Correct Answer)

Explanation: Explanation: Glucose-6-Phosphate Dehydrogenase (G6PD) deficiency is an X-linked recessive disorder where erythrocytes cannot generate sufficient NADPH to maintain reduced glutathione [1]. This leaves hemoglobin vulnerable to oxidative stress, leading to the formation of Heinz bodies and subsequent hemolysis when exposed to certain triggers. Why Pyrimethamine is the Correct Answer: Pyrimethamine is a dihydrofolate reductase inhibitor primarily used for toxoplasmosis and malaria. Unlike many other antimalarials, it does not possess significant oxidative properties and is considered **safe** to use in patients with G6PD deficiency. It does not induce the oxidative stress required to cause hemolysis in these patients. Analysis of Incorrect Options: * **Primaquine:** This is the classic "high-yield" trigger. It is a potent oxidizing agent used for the radical cure of *P. vivax* and *P. ovale*. It is strictly contraindicated in G6PD deficiency as it causes severe acute hemolytic anemia. * **Chloroquine:** While the risk is lower than with Primaquine, Chloroquine is an aminoquinoline that can trigger hemolysis in individuals with severe variants of G6PD deficiency (e.g., the Mediterranean variant). * **Quinine:** Similar to other cinchona alkaloids, Quinine can induce oxidative stress in red blood cells and is traditionally listed as a drug to be avoided or used with extreme caution in G6PD-deficient patients. NEET-PG High-Yield Pearls: * **Common Triggers:** Mnemonic **"SAPH"** — **S**ulfonamides, **A**ntimalarials (Primaquine), **P**yridium (Phenazopyridine), and **H**igh-dose Aspirin/Nitrofurantoin. Fava beans are the classic dietary trigger. * **Diagnosis:** Peripheral smear shows **"Bite cells"** (degmacytes) and **Heinz bodies** (denatured hemoglobin) visualized with supravital stains like Crystal Violet. * **Inheritance:** X-linked recessive; most common in populations from the Mediterranean and Africa (protective against malaria) [1].

Question 769: Which of the following is another name for lysosomes?

A. Suicide bags of cell
B. Residual bodies
C. Both A and B (Correct Answer)
D. None of the above

Explanation: **Explanation:** Lysosomes are membrane-bound spherical organelles containing acid hydrolases responsible for intracellular digestion. They are known by several names based on their physiological state and function: 1. **Suicide Bags of the Cell:** This term is used because lysosomes contain potent digestive enzymes (like proteases, nucleases, and lipases). If the lysosomal membrane ruptures, these enzymes are released into the cytoplasm, leading to autolysis (self-digestion) and cell death. 2. **Residual Bodies (Tertiary Lysosomes):** After the lysosome completes the digestion of exogenous or endogenous material, the indigestible remains are left within the vesicle. These are termed "residual bodies." In long-lived cells like neurons or cardiac muscle, these can persist as **lipofuscin granules** (the "wear-and-tear" pigment). **Analysis of Options:** * **Option A & B:** Both are scientifically accurate synonyms/functional descriptions of lysosomes. * **Option C:** This is the correct choice as it encompasses both the protective/destructive role (Suicide bags) and the post-digestive state (Residual bodies). **Clinical Pearls for NEET-PG:** * **Marker Enzyme:** Acid phosphatase is the classic marker for lysosomes. * **pH:** Lysosomes maintain an acidic internal environment (pH ~5.0) via a proton pump ($H^+$-ATPase). * **I-Cell Disease:** A deficiency in the Golgi enzyme (phosphotransferase) that tags proteins with Mannose-6-Phosphate, leading to the secretion of lysosomal enzymes extracellularly rather than targeting them to lysosomes. * **Lysosomal Storage Disorders:** Examples include Gaucher’s, Tay-Sachs, and Niemann-Pick disease, characterized by the accumulation of undigested substrates within lysosomes [1].

Question 770: Severe pain that arises after injury to or sectioning of a peripheral sensory nerve is called as?

A. Temporal arteritis
B. Neuralgia
C. Neuritis
D. Causalgia (Correct Answer)

Explanation: **Explanation:** **Correct Answer: D. Causalgia** Causalgia (now clinically referred to as **Complex Regional Pain Syndrome Type II**) is a syndrome of sustained burning pain, allodynia, and hyperpathia following a traumatic lesion of a peripheral nerve [1]. It most commonly occurs after injuries to nerves containing a high density of sympathetic fibers, such as the **median** or **tibial nerves**. The underlying mechanism involves "cross-talk" (ephaptic transmission) between efferent sympathetic fibers and afferent sensory fibers at the site of injury, leading to a state of chronic, intense pain often accompanied by vasomotor and sudomotor changes (e.g., sweating, skin color changes) [1]. **Why other options are incorrect:** * **A. Temporal arteritis:** This is an inflammatory disease of large and medium-sized systemic arteries (vasculitis), typically affecting the superficial temporal artery. It presents with headaches and jaw claudication, not peripheral nerve injury. * **B. Neuralgia:** This is a general term for pain that follows the distribution of a nerve (e.g., Trigeminal neuralgia). While it involves nerve pain, it does not specifically denote the severe, burning post-traumatic syndrome characteristic of causalgia. * **C. Neuritis:** This refers to the inflammation of a nerve. While it can cause pain and sensory loss, it is a pathological state (often due to infection or toxins) rather than a specific post-traumatic pain syndrome. **High-Yield Clinical Pearls for NEET-PG:** * **CRPS Type I (Reflex Sympathetic Dystrophy):** Occurs **without** a definable nerve injury (e.g., after a minor sprain or fracture). * **CRPS Type II (Causalgia):** Occurs **with** a specific, identifiable nerve injury [1]. * **Key Feature:** The pain is "out of proportion" to the inciting event and often relieved by a sympathetic nerve block.

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