Anatomy
3 questionsWhich nucleus is primarily involved in the Papez circuit?
Which thalamic nuclei can produce basal ganglia symptoms?
All are infraclavicular branches of brachial plexus except ?
NEET-PG 2013 - Anatomy NEET-PG Practice Questions and MCQs
Question 351: Which nucleus is primarily involved in the Papez circuit?
- A. Pulvinar nucleus
- B. Intralaminar nucleus
- C. Anterior nucleus of the thalamus (Correct Answer)
- D. Ventral posterolateral (VPL) nucleus
Explanation: ***Anterior nucleus of the thalamus*** - The **anterior nucleus of the thalamus** is a key relay station in the Papez circuit [1], receiving input from the mamillary bodies and projecting to the cingulate gyrus. - This circuit is crucial for **memory formation** [2] and emotional processing. *Pulvinar nucleus* - The pulvinar nucleus is primarily involved in **visual processing**, attention, and eye movements. - It does not form a direct part of the classic Papez circuit for emotion and memory. *Intralaminar nucleus* - The intralaminar nuclei are involved in **arousal**, attention, and pain perception, with widespread projections to the cerebral cortex [1]. - They are not considered a primary component of the Papez circuit. *Ventral posterolateral (VPL) nucleus* - The VPL nucleus is a major **somatosensory relay** in the thalamus, transmitting touch, proprioception, and vibration information from the body to the cortex. - It has no direct role in the Papez circuit or limbic functions.
Question 352: Which thalamic nuclei can produce basal ganglia symptoms?
- A. Lateral dorsal
- B. Pulvinar
- C. Ventral anterior (Correct Answer)
- D. Intralaminar
Explanation: ***Ventral anterior*** - The **ventral anterior (VA)** and **ventral lateral (VL)** nuclei of the thalamus receive significant input from the **basal ganglia** and project to the motor cortex [1]. - Dysfunction in these nuclei can disrupt the basal ganglia's influence on motor control, leading to symptoms like **dyskinesia** or **rigidity** [1]. *Lateral dorsal* - The **lateral dorsal nucleus** is primarily involved in **limbic system** functions and episodic memory. - It does not have direct nor significant connections with the basal ganglia motor circuits that would produce typical basal ganglia symptoms. *Pulvinar* - The **pulvinar** is the largest thalamic nucleus, primarily involved in **visual processing**, attention, and eye movements. - While it has extensive cortical connections, it is not directly involved in the motor circuits of the basal ganglia. *Intralaminar* - The **intralaminar nuclei** (e.g., centromedian and parafascicular) receive input from the basal ganglia but primarily project diffusely to the cerebral cortex and are involved in **arousal** and consciousness [2]. - While they modulate cortical activity, their dysfunction typically wouldn't produce the classic motor symptoms associated with basal ganglia disorders.
Question 353: All are infraclavicular branches of brachial plexus except ?
- A. Axillary nerve
- B. Thoracodorsal nerve
- C. Long thoracic nerve (Correct Answer)
- D. Ulnar nerve
Explanation: Long thoracic nerve - The long thoracic nerve originates directly from the roots (C5, C6, C7) of the brachial plexus, making it a supraclavicular branch. - It does not arise from the cords of the brachial plexus, which are located infraclavicularly. Ulnar nerve - The ulnar nerve arises from the medial cord of the brachial plexus, which is an infraclavicular structure. - It supplies many intrinsic hand muscles and the ulnar half of the flexor digitorum profundus. Axillary nerve - The axillary nerve is a branch of the posterior cord of the brachial plexus, classifying it as an infraclavicular branch. - It innervates the deltoid and teres minor muscles. Thoracodorsal nerve - The thoracodorsal nerve also originates from the posterior cord of the brachial plexus, making it an infraclavicular branch [1]. - It provides motor innervation to the latissimus dorsi muscle [1].
Pathology
1 questionsWhat are Councilman bodies and in which condition are they typically observed?
NEET-PG 2013 - Pathology NEET-PG Practice Questions and MCQs
Question 351: What are Councilman bodies and in which condition are they typically observed?
- A. Wilson's disease
- B. Ballooning degeneration of hepatocytes
- C. Acute viral hepatitis (Correct Answer)
- D. Alcoholic liver disease
Explanation: **Option G*****Acute viral hepatitis*** - Councilman bodies are **characteristic histological findings** in acute viral hepatitis, associated with apoptotic hepatocytes [1]. - They represent **necrosis** of liver cells, which is commonly seen during the acute phase of viral infections affecting the liver [1]. *Alcoholic cirrhosis* - While liver damage is present, Councilman bodies are not typical; they are more associated with acute conditions rather than the chronic nature of cirrhosis. - **Fibrosis** and **bridging necrosis** are evident in alcoholic cirrhosis, distinct from the **acute necrotic changes** seen in viral hepatitis. *Ballooning of cells - Damaged cells show diffuse swelling known as ballooning degeneration.* - Ballooning degeneration indicates **cellular swelling**, often noted in conditions like steatosis or alcoholic liver disease, but does not lead to the formation of Councilman bodies. - These changes are different from the **pyknotic or karyolytic changes** associated with Councilman bodies in acute infections. *Hepatic cell necrosis - The necrosis is usually focal or centirzonal.* - This refers to various types of necrosis in the liver but does not specifically indicate the presence of Councilman bodies, which are linked with apoptotic cells. - While necrosis is common in hepatic pathology, Councilman bodies are particularly associated with **viral hepatitis**. *Wilson's disease* - Although it causes liver damage, it typically results in **copper accumulation** and associated features, not specifically Councilman bodies in its pathology. - The findings in Wilson's disease include **hepatocellular degeneration** without the distinct apoptotic features seen in **acute viral hepatitis**. Option F*Autoimmune hepatitis* - This condition may cause liver cell damage and necrosis but does not typically show Councilman bodies in its histological profile. - It primarily shows **interface hepatitis** and **lymphocytic infiltration**, contrasting with the **apoptotic bodies** seen in acute viral scenarios. **References:** [1] Cross SS. Underwood's Pathology: A Clinical Approach. 6th ed. Common Clinical Problems From Liver And Biliary System Disease, pp. 386-387.
Pediatrics
2 questionsAt what age does the tonic neck reflex typically disappear?
What is the significance of the persistence of the asymmetric tonic neck reflex in a 9-month-old infant?
NEET-PG 2013 - Pediatrics NEET-PG Practice Questions and MCQs
Question 351: At what age does the tonic neck reflex typically disappear?
- A. 1 month
- B. 2 months
- C. 3 months
- D. 4 months (Correct Answer)
Explanation: ***Correct Answer: 4 months*** - The **tonic neck reflex**, also known as the **asymmetrical tonic neck reflex (ATNR)**, typically disappears around **4 to 6 months of age**. - Persistence beyond this age can be a sign of **neurological dysfunction** and may interfere with motor development such as rolling or bringing hands to midline. *Incorrect: 1 month* - While the tonic neck reflex is present at 1 month, it does not typically disappear at this early stage. - At 1 month, infants are still relying on a variety of **primitive reflexes** for survival and early motor patterns. *Incorrect: 2 months* - The tonic neck reflex is still usually clearly present at 2 months of age. - This reflex contributes to early **eye-hand coordination** and helps develop unilateral body movements. *Incorrect: 3 months* - While starting to integrate, the tonic neck reflex is not fully integrated or gone by 3 months. - Its presence is normal at this age, and its integration is a gradual process as **voluntary motor control** emerges.
Question 352: What is the significance of the persistence of the asymmetric tonic neck reflex in a 9-month-old infant?
- A. Decreased muscle tone
- B. Increased muscle tone (Correct Answer)
- C. Normal phenomenon
- D. None of the options
Explanation: ***Increased muscle tone*** - The **asymmetric tonic neck reflex (ATNR)** should integrate by **6 months of age**, and its persistence beyond this period is a sign of **neurological dysfunction**. - Persistent primitive reflexes, including ATNR, are often associated with **upper motor neuron lesions** and can manifest as increased muscle tone or **spasticity**. *Decreased muscle tone* - **Decreased muscle tone**, or **hypotonia**, is typically associated with **lower motor neuron lesions** or certain genetic conditions, not the persistence of primitive reflexes. - While some neurological conditions can cause hypotonia, persistent ATNR is a hallmark of problems leading to **hypertonia**. *Normal phenomenon* - The persistence of the ATNR beyond **6 months of age** is considered abnormal and indicates a potential developmental delay or neurological issue. - In a **9-month-old**, the reflex should have fully integrated, and its presence warrants further investigation. *None of the options* - As the persistence of the ATNR is indeed a significant finding, associated with increased muscle tone, this option is incorrect.
Physiology
4 questionsWhat type of reflex is the righting reflex?
Which of the following statements is true regarding post-ganglionic parasympathetic fibers?
Which of the following fiber types is classically categorized as Group B nerve fibers?
Spinal pathway mainly regulating fine motor activity?
NEET-PG 2013 - Physiology NEET-PG Practice Questions and MCQs
Question 351: What type of reflex is the righting reflex?
- A. Postural reflex (Correct Answer)
- B. Spinal reflex
- C. Ocular reflex
- D. Stretch reflex
Explanation: ***Postural reflex*** - The **righting reflex** is a mechanism that helps an animal or human maintain or regain their upright body position or head orientation in space, which is a key component of **postural control**. - It involves complex inputs from the **vestibular system**, visual system, and proprioceptors to adjust muscle tone and body position against gravity. - Examples include **neck righting reflex**, **body righting reflex**, and **labyrinthine righting reflex**. *Stretch reflex* - A **stretch reflex** is a monosynaptic reflex that causes a muscle to contract in response to being stretched, primarily to maintain muscle length and tone. - It does not encompass the complex, multi-sensory integration required for maintaining overall body orientation. *Spinal reflex* - A **spinal reflex** is any reflex arc whose neural circuit passes through the spinal cord, and it can be either monosynaptic or polysynaptic. - While the righting reflex involves spinal cord components, it is a broader, more integrated reflex that extends beyond a simple spinal cord circuit. *Ocular reflex* - **Ocular reflexes** are involuntary eye movements or responses, such as pupillary light reflex or vestibulo-ocular reflex, that primarily control eye position or pupil size. - They do not directly relate to the maintenance of the entire body's upright posture.
Question 352: Which of the following statements is true regarding post-ganglionic parasympathetic fibers?
- A. They originate from the spinal cord.
- B. They are part of the sympathetic nervous system.
- C. They are responsible for 'fight or flight' responses.
- D. They release acetylcholine at the target organs. (Correct Answer)
Explanation: ***They release acetylcholine at the target organs.*** - Post-ganglionic parasympathetic fibers are **cholinergic**, meaning they release the neurotransmitter **acetylcholine** at their effector organs. - This action mediates the characteristic "rest and digest" responses of the parasympathetic nervous system. *They originate from the spinal cord.* - **Pre-ganglionic parasympathetic fibers** originate from the **brainstem** (cranial nerves III, VII, IX, X) and the **sacral spinal cord** (S2-S4). - Post-ganglionic fibers originate in ganglia located near or within their target organs, not the spinal cord directly. *They are part of the sympathetic nervous system.* - Post-ganglionic parasympathetic fibers are a component of the **parasympathetic nervous system**, not the sympathetic nervous system. - The sympathetic and parasympathetic systems are distinct divisions of the autonomic nervous system with generally opposing functions. *They are responsible for 'fight or flight' responses.* - The **'fight or flight' response** is characteristic of the **sympathetic nervous system**, which prepares the body for stressful situations. - The parasympathetic nervous system is responsible for **'rest and digest' functions**, promoting energy conservation and maintenance activities.
Question 353: Which of the following fiber types is classically categorized as Group B nerve fibers?
- A. Sympathetic postganglionic
- B. Parasympathetic preganglionic
- C. Parasympathetic post ganglionic
- D. Sympathetic preganglionic (Correct Answer)
Explanation: ***Sympathetic preganglionic*** - **Group B nerve fibers** are **myelinated preganglionic autonomic fibers** with intermediate diameter (3-15 μm) and moderate conduction velocity (3-15 m/s) - Both **sympathetic and parasympathetic preganglionic fibers** are classified as Group B fibers - **Sympathetic preganglionic** neurons are the classical example, originating from T1-L2 spinal segments and synapsing in paravertebral or prevertebral ganglia *Sympathetic postganglionic* - These are **unmyelinated Group C fibers** with slow conduction velocity (0.5-2 m/s) - They extend from ganglia to target organs *Parasympathetic preganglionic* - These are also **Group B fibers** (myelinated preganglionic) - However, **sympathetic preganglionic** is the more commonly cited classical example in standard classifications - They originate from cranial nerves (III, VII, IX, X) and sacral segments (S2-S4) *Parasympathetic postganglionic* - These are **unmyelinated Group C fibers** with the slowest conduction velocities - Short fibers extending from ganglia near or within target organs to effector cells
Question 354: 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