Neuroanatomy Practice Questions

Q: What is true about the vestibular nerve?

All of the above.. The vestibular nerve (CN VIII) is a critical component of the vestibulocochlear system, responsible for maintaining equilibrium and balance [1]. **Explanation of Options:** * **Option A (Nucleus supply):** The vestibular nuclei are located in the floor of the fourth ventricle, primarily within the medulla and pons. This region, specifically the lateral part of the medulla and inferior pons, receives its arterial supply from the **Posterior Inferior Cerebellar Artery (PICA)** and the Anterior Inferior Cerebellar Artery (AICA). * **Option B (Facial nerve connection):** Within the internal acoustic meatus, there is a known **vestibulofascial anastomosis** (Oort’s anastomosis). This connection involves fibers passing between the vestibular nerve and the facial nerve (CN VII), which is clinically relevant in cases of viral spread (e.g., Ramsay Hunt Syndrome). * **Option C (Scarpa’s ganglion):** The cell bodies of the first-order sensory neurons of the vestibular nerve are located in the **vestibular ganglion**, which is eponymously known as **Scarpa’s ganglion** [1]. It is situated at the distal end of the internal acoustic meatus [1]. **Conclusion:** Since all statements are anatomically accurate, **Option D** is the correct answer. **High-Yield NEET-PG Pearls:** * **Internal Acoustic Meatus (IAM):** Contains CN VII, CN VIII, and the Labyrinthine artery. * **Orientation in IAM:** The vestibular nerve is situated posteriorly (Superior and Inferior divisions), while the facial nerve is "7-up" (anterosuperior) and the cochlear nerve is "Coke-down" (anteroinferior). * **Blood Supply:** Occlusion of the **PICA** leads to **Wallenberg Syndrome** (Lateral Medullary Syndrome), which presents with vertigo and nystagmus due to involvement of the vestibular nuclei [1].

Q: The spinal tract involved with the control of trunk muscles is:

Anterior corticospinal. ### Explanation **Correct Answer: A. Anterior corticospinal** The **Anterior Corticospinal Tract (ACT)** is a descending motor pathway primarily responsible for the control of **axial (trunk) and proximal limb muscles** [1]. Unlike the lateral corticospinal tract, which decussates in the medulla, the fibers of the ACT remain uncrossed in the spinal cord until they reach their target level [1]. At the segmental level, they decussate through the anterior white commissure to synapse on bilateral lower motor neurons. This bilateral innervation ensures coordinated postural control and stability of the trunk. **Why other options are incorrect:** * **B. Anterior spinocerebellar:** This is an **ascending (sensory)** tract that carries unconscious proprioceptive information from the lower limbs to the cerebellum. It is not involved in motor control of the trunk. * **C. Cuneocerebellar:** This is an **ascending** tract that carries unconscious proprioception from the upper limbs (above T6) to the cerebellum via the accessory cuneate nucleus. * **D. Lateral corticospinal:** While this is a motor tract, it decussates at the medullary pyramids and is primarily responsible for **fine, skilled movements of the distal extremities** (e.g., fingers) [1]. **High-Yield Clinical Pearls for NEET-PG:** * **Decussation:** 80–90% of corticospinal fibers cross at the medulla (Lateral tract); the remaining 10–20% form the Anterior tract [1]. * **Somatotopic Organization:** In the spinal cord, the lateral corticospinal tract is organized such that sacral fibers are most peripheral, while cervical fibers are more central [1]. * **Clinical Sign:** Lesions of the corticospinal tracts result in **Upper Motor Neuron (UMN)** signs: spasticity, hyperreflexia, and a positive Babinski sign [1].

Q: The genu of the internal capsule contains which of the following?

Sensory fibers from the thalamus to the cerebral cortex. The **internal capsule** is a compact bundle of white matter fibers that separates the thalamus and caudate nucleus from the lentiform nucleus. Understanding its topographical organization is high-yield for NEET-PG. ### Why Option A is Correct The **genu** (the "knee" or bend) of the internal capsule primarily contains **corticobulbar (corticonuclear) fibers**, which carry motor commands to the cranial nerve nuclei [1]. However, it also contains **thalamocortical fibers** (sensory radiations) traveling from the ventral anterior and ventral lateral nuclei of the thalamus to the motor and premotor cortex. Among the given options, sensory fibers from the thalamus to the cortex are a recognized constituent of the genu. ### Why Other Options are Incorrect Options B, C, and D refer to the **corticospinal tract (CST)**. The CST is organized somatotopically within the **posterior limb** of the internal capsule, not the genu: * **Upper limb fibers:** Located in the anterior part of the posterior limb. * **Trunk fibers:** Located in the middle part of the posterior limb. * **Lower limb fibers:** Located in the posterior part of the posterior limb. ### NEET-PG High-Yield Pearls * **Anterior Limb:** Contains frontopontine fibers and the anterior thalamic radiation. * **Posterior Limb:** Contains the corticospinal tract, sensory fibers (superior thalamic radiation), and visual/auditory radiations. * **Retrolentiform Part:** Contains the optic radiation (lateral geniculate body to visual cortex). * **Sublentiform Part:** Contains the auditory radiation (medial geniculate body to auditory cortex). * **Clinical Correlation:** A stroke involving the **Charcot’s artery** (Lenticulostriate artery) often affects the internal capsule, leading to contralateral hemiplegia [1]. If the genu is involved, it results in pseudobulbar palsy symptoms due to corticobulbar fiber damage.

Q: What is true about the corpus callosum?

Unites the far areas of the two sides of the brain.. The **Corpus Callosum** is the largest commissural fiber bundle in the brain, consisting of approximately 200 million axons. Its primary function is to facilitate interhemispheric communication. ### **Explanation of Options** * **Correct Answer (A):** The corpus callosum primarily connects **homologous (mirror-image) areas** of the two cerebral hemispheres. However, its specific functional role is to integrate information between "far" or distant cortical regions across the midline, allowing the two sides of the brain to function as a single unit. * **Option B:** While it does connect the frontal lobes (via the *Genu* and *Rostrum*), it also connects the parietal, temporal, and occipital lobes. Restricting its function to only the frontal lobes is incomplete. * **Option C:** While it "connects" the hemispheres, the term "unites" in neuroanatomical nomenclature often refers to the functional integration of distant cortical points, making Option A a more precise description of its physiological role. * **Option D:** The **Indusium griseum** (a thin layer of primitive gray matter) and the medial/lateral longitudinal striae are located **superior** to the corpus callosum. Therefore, the corpus callosum is *inferiorly* related to the Indusium griseum, not superiorly. ### **High-Yield Clinical Pearls for NEET-PG** 1. **Parts (Anterior to Posterior):** Rostrum $\rightarrow$ Genu $\rightarrow$ Body (Trunk) $\rightarrow$ Splenium. 2. **Forceps Minor:** Fibers of the **Genu** connecting the frontal lobes. 3. **Forceps Major:** Fibers of the **Splenium** connecting the occipital lobes. 4. **Tapetum:** Fibers of the trunk and splenium that form the roof and lateral wall of the posterior and inferior horns of the lateral ventricle. 5. **Clinical Correlation:** Surgical sectioning (Callosotomy) is used to treat intractable epilepsy to prevent the spread of seizure activity (Split-brain syndrome).

Q: Parasympathetic fibers of the vagus nerve supply which of the following structures?

Heart. **Explanation:** The **Vagus nerve (CN X)** is the longest cranial nerve and provides extensive parasympathetic (craniosacral) innervation to thoracic and abdominal viscera [1]. Its preganglionic parasympathetic fibers originate in the **Dorsal Nucleus of Vagus** and the **Nucleus Ambiguus** [1]. 1. **Why Heart is Correct:** The vagus nerve provides parasympathetic supply to the heart via cardiac branches [1]. These fibers synapse in ganglia located within the cardiac plexus and the atrial walls [2]. Stimulation results in a decreased heart rate (negative chronotropy) and decreased conduction velocity through the AV node [3]. 2. **Why other options are incorrect:** * **Parotid Gland:** Supplied by the **Glossopharyngeal nerve (CN IX)**. Fibers originate in the inferior salivatory nucleus and synapse in the **otic ganglion** [2]. * **Submandibular Gland:** Supplied by the **Facial nerve (CN VII)** via the chorda tympani branch. Fibers originate in the superior salivatory nucleus and synapse in the **submandibular ganglion** [2]. * **Ciliary Muscles:** Supplied by the **Oculomotor nerve (CN III)**. Fibers originate in the Edinger-Westphal nucleus and synapse in the **ciliary ganglion** [2]. **High-Yield NEET-PG Pearls:** * **The "Rule of 2/3rds":** The vagus nerve supplies the midgut up to the junction of the proximal 2/3rds and distal 1/3rd of the transverse colon. Beyond this point (hindgut), parasympathetic supply is taken over by the **Pelvic Splanchnic Nerves (S2-S4)**. * **Nucleus Ambiguus:** This nucleus provides the special visceral efferent (SVE) fibers to the muscles of the larynx and pharynx, but also contains the cell bodies for preganglionic parasympathetic cardiac inhibitory fibers [1]. * **Vagal Maneuvers:** Clinical techniques (like carotid sinus massage) increase vagal tone to terminate Supraventricular Tachycardia (SVT).

Q: Which nucleus is not found in the floor of the fourth ventricle?

None of the above. The floor of the fourth ventricle, also known as the **rhomboid fossa**, is formed by the dorsal surfaces of the pons and the open part of the medulla oblongata. It contains several elevations produced by underlying cranial nerve nuclei. ### Explanation of the Correct Answer The correct answer is **D (None of the above)** because all the listed nuclei (Abducens, Dorsal Vagal, and Hypoglossal) are indeed located in the floor of the fourth ventricle. They create distinct anatomical landmarks visible on its surface. ### Analysis of Options * **Abducens Nucleus (Option A):** Located in the upper (pontine) part of the floor. It is covered by the fibers of the facial nerve, which together form the **facial colliculus** in the medial eminence. * **Hypoglossal Nucleus (Option C):** Located in the lower (medullary) part of the floor. It lies deep to the **hypoglossal triangle**, situated medial to the vagal triangle. * **Dorsal Vagal Nucleus (Option B):** Also located in the medullary part of the floor. It lies deep to the **vagal triangle** (ala cinerea), situated lateral to the hypoglossal triangle. ### NEET-PG High-Yield Pearls * **Area Postrema:** A chemoreceptor trigger zone (CTZ) located at the inferior angle of the floor, just lateral to the vagal triangle. It lacks a blood-brain barrier. * **Locus Coeruleus:** A bluish-gray area in the upper part of the floor (superior fovea) containing noradrenergic neurons. * **Striae Medullares:** Transverse nerve fibers that divide the floor into a superior pontine part and an inferior medullary part. * **Vestibular Nuclei:** These lie deep to the **vestibular area**, which occupies the lateral-most part of the floor in both the pons and medulla.

Q: What is the origin of sympathetic fibres?

Dorsolumbar. **Explanation:** The Autonomic Nervous System (ANS) is divided into the sympathetic and parasympathetic divisions based on their anatomical origin and physiological functions. **Why "Dorsolumbar" is correct:** The sympathetic nervous system is anatomically characterized as the **Thoracolumbar (Dorsolumbar) outflow**. The preganglionic sympathetic neurons originate in the **Intermediolateral (IML) gray column** of the spinal cord, specifically from segments **T1 to L2 (or L3)**. These fibers exit via the ventral roots to reach the sympathetic chain or collateral ganglia. **Why other options are incorrect:** * **Cranial & Sacral (Options A & B):** These represent the **Craniosacral outflow**, which is the anatomical origin of the **Parasympathetic nervous system**. * *Cranial part:* Originates from cranial nerve nuclei III (Oculomotor), VII (Facial), IX (Glossopharyngeal), and X (Vagus). * *Sacral part:* Originates from spinal segments S2, S3, and S4 (Pelvic splanchnic nerves). **High-Yield NEET-PG Pearls:** 1. **Neurotransmitters:** All preganglionic fibers (both sympathetic and parasympathetic) release **Acetylcholine (ACh)**. Most postganglionic sympathetic fibers release **Norepinephrine**, except for those supplying sweat glands (which use ACh). 2. **Fiber Length:** Sympathetic nerves typically have **short preganglionic** and **long postganglionic** fibers (due to the proximity of the sympathetic chain to the spinal cord). 3. **Adrenal Medulla:** It is considered a modified sympathetic ganglion; its cells (chromaffin cells) are postganglionic neurons that lack axons and secrete epinephrine directly into the blood.

Question 1

What is true about the vestibular nerve?

Accepted Answer

All of the above.

Answer

Its nucleus is supplied by the PICA.

Answer

It has an anastomotic connection with the facial nerve.

Answer

The vestibular ganglion is also called Scarpa's ganglion.

Question 2

The spinal tract involved with the control of trunk muscles is:

Accepted Answer

Anterior corticospinal

Answer

Anterior spinocerebellar

Answer

Cuneocerebellar

Answer

Lateral corticospinal

Question 3

All of the following are true about the vestibular nerve except:

Accepted Answer

The nucleus lies in the midbrain near the cerebral aqueduct.

Answer

It has two divisions: superior and inferior vestibular.

Answer

The vestibular nuclei are situated at the junction of the pons and medulla.

Answer

Nerve fibers relay at Scarpa's ganglion.

Question 4

The genu of the internal capsule contains which of the following?

Accepted Answer

Sensory fibers from the thalamus to the cerebral cortex

Answer

Motor fibers from the cerebral cortex to the lower limb

Answer

Motor fibers from the cerebral cortex to the upper limb

Answer

Motor fibers from the cerebral cortex to the trunk

Question 5

Which neuroanatomical part of the brain is involved in sexual drive?

Accepted Answer

Limbic system

Answer

Temporal lobe

Answer

Hypothalamus

Answer

Frontal lobe

Question 6

What is true about the corpus callosum?

Accepted Answer

Unites the far areas of the two sides of the brain.

Answer

Connects the two frontal lobes.

Answer

Unites the two hemispheres.

Answer

Is superiorly related to the Indusium griseum.

Question 7

Parasympathetic fibers of the vagus nerve supply which of the following structures?

Accepted Answer

Heart

Answer

Parotid gland

Answer

Submandibular gland

Answer

Ciliary muscles

Question 8

A 55-year-old right-handed veteran received a small shrapnel wound in the head. Within 1 year of receiving his wound, the man complained of seizures and was treated with seizure medication. The medication was not effective, and a section of the anterior corpus callosum was performed. Which of the following neurologic deficits is most likely?

Accepted Answer

The inability, with closed eyes, to identify verbally an object held in the left hand

Answer

Alexia

Answer

Gait ataxia

Answer

Loss of binocular vision

Question 9

Which nucleus is not found in the floor of the fourth ventricle?

Accepted Answer

None of the above

Answer

Abducens nucleus

Answer

Dorsal vagal nuclei

Answer

Hypoglossal nucleus

Question 10

What is the origin of sympathetic fibres?

Accepted Answer

Dorsolumbar

Answer

Cranial

Answer

Sacral

Answer

None

Neuroanatomy — MCQs

Neuroanatomy — MCQs

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