Neuroanatomy — MCQs

Neuroanatomy Indian Medical PG Practice Questions and MCQs

Question 991: Injury to the corpus striatum leads to which of the following motor disorders?

A. Chorea (Correct Answer)
B. Parkinsonism
C. Hemiballismus
D. Athetosis

Explanation: The **Corpus Striatum** (comprising the Caudate Nucleus and Putamen) is the primary input station of the Basal Ganglia [1]. It plays a crucial role in regulating voluntary movement by inhibiting unwanted motor activity. **1. Why Chorea is the Correct Answer:** Chorea is characterized by brief, semi-directed, irregular, and involuntary movements. It is classically associated with lesions of the **Corpus Striatum** (specifically the Caudate Nucleus). In conditions like **Huntington’s Disease**, the degeneration of GABAergic neurons in the striatum leads to a loss of inhibitory control over the motor thalamus, resulting in the hyperkinetic movements seen in Chorea [1]. **2. Analysis of Incorrect Options:** * **Parkinsonism:** This is primarily caused by the degeneration of dopaminergic neurons in the **Substantia Nigra pars compacta (SNpc)**, leading to a deficiency of dopamine in the striatum [1]. * **Hemiballismus:** This involves violent, flinging movements of the limbs and is specifically caused by a lesion in the **Subthalamic Nucleus (STN)**. * **Athetosis:** This refers to slow, writhing, "worm-like" movements, typically associated with lesions in the **Globus Pallidus**. **Clinical Pearls for NEET-PG:** * **Caudate Nucleus + Putamen** = Neostriatum (Corpus Striatum) [2]. * **Putamen + Globus Pallidus** = Lentiform Nucleus. * **Wilson’s Disease** typically affects the Putamen (Lenticular degeneration). * **Sydenham’s Chorea** is a major criterion for Rheumatic Fever, caused by autoimmune damage to the basal ganglia.

Question 992: The transtubercular plane lies at which vertebral level?

A. L1
B. L3
C. L5 (Correct Answer)
D. S3

Explanation: The **transtubercular plane** is a horizontal anatomical plane passing through the iliac tubercles on the iliac crest of the pelvis. It is located at the level of the **L5 vertebral body**. This plane is clinically significant as it marks the upper boundary of the hypogastric (pubic) and iliac (inguinal) regions in the nine-region classification of the abdomen. **Analysis of Options:** * **L1 (Incorrect):** This is the level of the **Transpyloric plane** (of Addison). It is a high-yield landmark passing through the pylorus of the stomach, the hila of the kidneys, and the beginning of the duodenum. * **L3 (Incorrect):** This is the level of the **Subcostal plane**, which joins the lowest points of the costal margins (10th costal cartilage). It is also the level of the inferior mesenteric artery origin. * **L5 (Correct):** The transtubercular plane passes through the tubercles of the iliac crest, corresponding to the L5 vertebra. It also roughly corresponds to the level where the **Inferior Vena Cava (IVC) is formed** by the union of the common iliac veins. * **S3 (Incorrect):** This level marks the beginning of the rectum and the end of the sigmoid colon. **NEET-PG High-Yield Pearls:** 1. **Supracristal Plane (L4):** Passes through the highest points of the iliac crests; used as a landmark for lumbar punctures. 2. **Umbilicus:** Usually located at the L3-L4 disc level. 3. **Aortic Bifurcation:** Occurs at the L4 level, just above the transtubercular plane. 4. **IVC Formation:** Occurs at the L5 level, coinciding with the transtubercular plane.

Question 993: What is mirabegron?

A. Alpha 2 agonist
B. Beta 3 agonist (Correct Answer)
C. Beta 1 agonist
D. Beta 2 agonist

Explanation: **Explanation:** **Mirabegron** is a potent and selective **Beta-3 ($\beta_3$) adrenergic receptor agonist**. In the context of neuroanatomy and autonomic pharmacology, $\beta_3$ receptors are primarily located on the **detrusor muscle** of the urinary bladder. Activation of these receptors stimulates adenylyl cyclase, increasing intracellular cAMP, which leads to detrusor muscle relaxation [1]. This increases bladder capacity and provides symptomatic relief for **Overactive Bladder (OAB)** without the dry mouth and constipation typically associated with anticholinergics. **Analysis of Incorrect Options:** * **Option A (Alpha-2 agonist):** These agents (e.g., Clonidine) act on presynaptic receptors in the CNS to decrease sympathetic outflow. They are used for hypertension or sedation, not bladder relaxation. * **Option C (Beta-1 agonist):** These receptors are primarily located in the heart. Agonists (e.g., Dobutamine) increase heart rate and contractility [1]. * **Option D (Beta-2 agonist):** These receptors are found in bronchial smooth muscle. Agonists (e.g., Salbutamol) are used for bronchodilation in asthma/COPD. **High-Yield Clinical Pearls for NEET-PG:** * **Clinical Use:** First-line alternative for Overactive Bladder (OAB) in patients who cannot tolerate antimuscarinics (like Oxybutynin). * **Side Effects:** The most significant side effect is **Hypertension**; it should be avoided in patients with severe uncontrolled high blood pressure. * **Mechanism:** It enhances the "filling/storage" phase of micturition by mimicking sympathetic stimulation of the detrusor.

Question 994: Taste fibres from the anterior two-thirds of the tongue are carried by which nerve?

A. Trigeminal nerve
B. Facial nerve (Correct Answer)
C. Hypoglossal nerve
D. Glossopharyngeal nerve

Explanation: The tongue’s innervation is a high-yield topic for NEET-PG, requiring a clear distinction between general sensation and special sensation (taste). [1] ### **Explanation** The **Facial nerve (CN VII)** is responsible for carrying taste fibers from the **anterior two-thirds** of the tongue. Specifically, these fibers travel via the **chorda tympani** nerve (a branch of CN VII), which joins the lingual nerve to reach the tongue. The cell bodies for these taste fibers are located in the **geniculate ganglion**, and they ultimately synapse in the nucleus tractus solitarius (NTS) in the brainstem. [1] ### **Analysis of Incorrect Options** * **A. Trigeminal nerve (CN V):** The lingual nerve (a branch of the mandibular division, V3) carries **general sensation** (touch, pain, temperature) from the anterior two-thirds, not taste. * **C. Hypoglossal nerve (CN XII):** This is a purely motor nerve responsible for the movements of all intrinsic and extrinsic muscles of the tongue (except the palatoglossus). * **D. Glossopharyngeal nerve (CN IX):** This nerve carries **both** taste and general sensation from the **posterior one-third** of the tongue, including the vallate papillae. [1] ### **High-Yield Clinical Pearls** * **Vagus Nerve (CN X):** Carries taste and general sensation from the extreme posterior part of the tongue (epiglottic region) via the internal laryngeal nerve. [1] * **Nucleus Tractus Solitarius (NTS):** The "sensory nucleus of the viscera" where all taste fibers (VII, IX, X) terminate. * **Clinical Correlation:** Damage to the facial nerve proximal to the branching of the chorda tympani (as seen in Bell’s Palsy) results in **ageusia** (loss of taste) in the anterior two-thirds of the tongue.

Question 995: Which of the following is a branch of the third part of the subclavian artery?

A. Thyrocervical trunk
B. Dorsal scapular artery (Correct Answer)
C. Vertebral artery
D. Internal thoracic artery

Explanation: The subclavian artery is divided into three parts by the **scalenus anterior muscle**: the first part is medial, the second part is posterior, and the third part is lateral to the muscle. ### **Explanation of the Correct Answer** **B. Dorsal Scapular Artery:** This is the most common branch of the **third part** of the subclavian artery. It passes through the brachial plexus to supply the levator scapulae and rhomboid muscles. *Note:* In about 30% of individuals, it arises as a deep branch of the transverse cervical artery (from the thyrocervical trunk); however, for NEET-PG purposes, it is classically taught as the branch of the third part. ### **Analysis of Incorrect Options** * **A. Thyrocervical Trunk:** Arises from the **first part** of the subclavian artery. It further divides into the inferior thyroid, suprascapular, and transverse cervical arteries. * **C. Vertebral Artery:** Arises from the **first part** (superior aspect). it ascends through the foramina transversaria of the cervical vertebrae to enter the cranial cavity. * **D. Internal Thoracic Artery:** Arises from the **first part** (inferior aspect). It descends behind the costal cartilages to supply the anterior chest wall and breast. ### **High-Yield NEET-PG Pearls** * **Mnemonic for Branches:** * **1st Part:** **V**ertebral, **I**nternal thoracic, **T**hyrocervical trunk (**VIT**). * **2nd Part:** **C**ostocervical trunk (**C**). * **3rd Part:** **D**orsal scapular artery (**D**). * **The Second Part:** Usually gives off only the **Costocervical trunk** (which divides into the superior intercostal and deep cervical arteries). * **Clinical Correlation:** The third part of the subclavian artery is the most superficial and can be compressed against the first rib to control bleeding in the upper limb.

Question 996: A 75-year-old coal miner complains of progressive loss of vision. Visual field examination shows visual loss in the upper right quadrant in both visual fields. The lesion would most likely be in which location?

A. Left cuneus
B. Left temporal lobe (Correct Answer)
C. Right angular gyrus
D. Right lingual gyrus

Explanation: **Explanation:** The patient presents with **Right Upper Quadrantopia** (Right Superior Quadrantanopia), colloquially known as a "pie in the sky" defect. This visual field deficit is pathognomonic for a lesion in the **Meyer’s Loop**. 1. **Why Option B is Correct:** Visual information from the **inferior retina** (which represents the **superior visual field**) travels via the lower fibers of the geniculocalcarine tract [1]. These fibers loop forward into the **temporal lobe** (Meyer’s Loop) before reaching the primary visual cortex [2]. Because the defect is on the right side, the lesion must be in the contralateral (**left**) hemisphere. Thus, a left temporal lobe lesion interrupts Meyer’s Loop, causing a right superior quadrantanopia. 2. **Why Other Options are Incorrect:** * **A. Left Cuneus:** The cuneus is the superior bank of the calcarine sulcus. It receives input from the superior retina (inferior visual field). A lesion here would cause a right *inferior* quadrantanopia ("pie on the floor") [2]. * **C. Right Angular Gyrus:** This area is involved in language and spatial cognition (Gerstmann syndrome). While located in the parietal lobe, a lesion here would typically affect the optic radiations (Baum’s loop), leading to an *inferior* quadrantanopia on the *left* side. * **D. Right Lingual Gyrus:** The lingual gyrus is the inferior bank of the calcarine sulcus. A lesion here would cause a *left* superior quadrantanopia. **NEET-PG High-Yield Pearls:** * **Temporal Lobe Lesion:** Meyer’s Loop → Superior Quadrantanopia ("Pie in the Sky") [2]. * **Parietal Lobe Lesion:** Baum’s Loop → Inferior Quadrantanopia ("Pie on the Floor"). * **Homonymous Hemianopia:** Occurs with lesions posterior to the optic chiasm (Optic tract or complete Lateral Geniculate Nucleus/Optic radiation destruction) [2]. * **Macular Sparing:** Characteristically seen in PCA territory infarcts involving the occipital cortex due to collateral supply from the MCA [2].

Question 997: Section 174 of the Criminal Procedure Code deals with which type of inquest?

A. Police inquest (Correct Answer)
B. Magistrate inquest
C. Coroner's inquest
D. Summons

Explanation: Explanation: In India, an **inquest** is a legal inquiry into the cause of death in cases that are sudden, suspicious, or unnatural. **Correct Option: A. Police Inquest** Under **Section 174 of the Criminal Procedure Code (CrPC)**, a police officer (usually the Station House Officer) conducts an investigation to determine the apparent cause of death. They prepare a report known as the **Panchnama**, which is signed by two or more respectable witnesses (Panchas). This is the most common type of inquest in India. **Incorrect Options:** * **B. Magistrate Inquest:** This is conducted under **Section 176 CrPC**. It is mandatory in specific high-risk scenarios such as custodial deaths, deaths in police firing, dowry deaths (within 7 years of marriage), or exhumations. It is superior to a police inquest. * **C. Coroner’s Inquest:** This system was abolished in India (previously active in Mumbai and Kolkata). It is currently practiced in countries like the UK and USA, where a specialized official (Coroner) investigates the death. * **D. Summons:** This is not a type of inquest; it is a legal document issued by a court ordering a person to appear as a witness or to produce documents. **High-Yield Clinical Pearls for NEET-PG:** * **Section 174 CrPC:** Police Inquest (Most common). * **Section 176 CrPC:** Magistrate Inquest (Custodial deaths/Dowry deaths). * **Section 175 CrPC:** Empowers the police to summon witnesses for the inquest. * **Medical Examiner System:** Considered the best system of inquest (practiced in parts of the USA), but not currently used in India.

Question 998: All of the following are true about an expert witness except?

A. A skilled person in a particular field.
B. Drawing inferences from observation.
C. Can claim conduct money.
D. Responsibility is less. (Correct Answer)

Explanation: In the context of Forensic Medicine (Medical Jurisprudence), an **Expert Witness** is a person who possesses specialized knowledge, skill, or experience in a specific field (e.g., a doctor, ballistics expert, or handwriting expert) and is called to assist the court in understanding technical evidence. ### Why "Responsibility is less" is the Correct Answer (The False Statement) The statement is incorrect because the responsibility of an expert witness is actually **higher** than that of a common witness. While a common witness only testifies to facts they perceived through their senses, an expert witness provides **opinions and inferences**. Their testimony can significantly influence the court's judgment regarding the cause of death, the nature of an injury, or the sanity of an accused. Therefore, they are held to a high standard of professional accountability. ### Explanation of Other Options * **A. A skilled person in a particular field:** This is the definition of an expert witness under **Section 45 of the Indian Evidence Act**. They are called when the court needs an opinion on points of foreign law, science, art, or identity. * **B. Drawing inferences from observation:** Unlike a command witness (who can only state what they saw/heard), an expert is legally permitted to draw conclusions and provide opinions based on their observations and professional findings. * **C. Can claim conduct money:** Conduct money is the fee paid to a witness to cover travel and incidental expenses. In civil cases, an expert witness can refuse to attend if conduct money is not paid in advance. ### NEET-PG High-Yield Pearls * **Common Witness:** Testifies only to facts (Section 60, IEA). * **Expert Witness:** Testifies to opinions/inferences (Section 45, IEA). * **Hostile Witness:** A witness who gives testimony against the party that called them (Section 154, IEA). * **Perjury:** Giving false evidence under oath; punishable under Section 193 of the IPC.

Question 999: What is the mechanism of action of pralidoxime?

A. Stimulation of acetylcholine receptors
B. Inhibition of acetylcholine breakdown
C. Blockade of acetylcholine receptors
D. Deactivation of acetylcholinesterase enzyme (Correct Answer)

Explanation: ### Explanation **Mechanism of Action: The Correct Answer** Pralidoxime (2-PAM) is a **cholinesterase reactivator** [1]. In organophosphate (OP) poisoning, the OP compound binds to the anionic site of the acetylcholinesterase (AChE) enzyme, phosphorylating it and rendering it inactive. Pralidoxime has a high affinity for the phosphate group; it binds to the enzyme-inhibitor complex, removes the phosphate group, and restores the enzyme's ability to degrade acetylcholine [1]. This process is known as **deactivation of the phosphorylated enzyme** (reactivation of the functional enzyme). **Analysis of Incorrect Options** * **Option A:** Pralidoxime does not stimulate receptors; its effect is indirect by restoring the enzyme that controls neurotransmitter levels. * **Option B:** This describes the effect of Organophosphates or Carbamates themselves, which lead to a cholinergic crisis [2]. Pralidoxime does the opposite. * **Option C:** This is the mechanism of **Atropine**, which competitively blocks muscarinic receptors to manage symptoms but does not fix the underlying enzyme inhibition. **NEET-PG High-Yield Pearls** * **The "Aging" Phenomenon:** Pralidoxime must be administered early [1]. Once the enzyme-OP bond "ages" (dealkylation), the bond becomes permanent, and oximes can no longer reactivate the enzyme [1]. * **Blood-Brain Barrier:** Pralidoxime is a quaternary ammonium compound and **does not cross the BBB**; therefore, it does not reverse central CNS symptoms (unlike Atropine) [1]. * **Specific Use:** It is effective in Organophosphate poisoning but is generally **not recommended for Carbamate poisoning** (as the carbamate-enzyme bond is reversible and oximes may worsen the inhibition). * **The "Double Therapy":** Management of OP poisoning always requires Atropine (to treat symptoms) + Pralidoxime (to restore enzyme function) [1].

Question 1000: Fanconi Bickel syndrome is associated with which of the following?

A. GLUT 1
B. GLUT 2 (Correct Answer)
C. GLUT 3
D. GLUT 4

Explanation: **Explanation:** **Fanconi-Bickel Syndrome (FBS)** is a rare autosomal recessive disorder of carbohydrate metabolism caused by a mutation in the **SLC2A2 gene**, which encodes the **GLUT 2** transporter. **Why GLUT 2 is the Correct Answer:** GLUT 2 is a high-capacity, low-affinity glucose transporter found primarily in the **liver, pancreas (beta cells), intestines, and proximal renal tubules** [1]. In FBS, the deficiency of GLUT 2 leads to: 1. **Impaired Glucose Export:** Glucose cannot leave the liver or kidneys, leading to glycogen accumulation (Hepatorenal Glycogenosis). 2. **Proximal Renal Tubular Dysfunction:** Failure to reabsorb glucose, amino acids, and phosphates, resulting in Fanconi syndrome (glycosuria, phosphaturia, and aminoaciduria) [1]. **Analysis of Incorrect Options:** * **GLUT 1:** Found in RBCs and the Blood-Brain Barrier [1]. Deficiency leads to encephalopathy and seizures (De Vivo disease). * **GLUT 3:** Primarily found in neurons (high affinity) [1]. It ensures glucose uptake in the brain even during hypoglycemia. * **GLUT 4:** The only **insulin-dependent** transporter, found in skeletal muscle and adipose tissue [1]. It is sequestered intracellularly and translocates to the membrane in response to insulin. **High-Yield Clinical Pearls for NEET-PG:** * **Clinical Triad of FBS:** Hepatomegaly (due to glycogen storage), Vitamin D-resistant rickets (due to phosphate loss), and fasting hypoglycemia with postprandial hyperglycemia. * **GLUT 2 Function:** Acts as a "glucose sensor" in pancreatic beta cells for insulin secretion [1]. * **SGLT vs. GLUT:** Remember that SGLT (1 & 2) are active transporters (sodium-dependent), while GLUTs are facilitated diffusion transporters [1].

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