Neuroanatomy Practice Questions

Q: Which of the following represents the efferent fibers of the amygdala?

Stria terminalis. The **amygdala** (amygdaloid nuclear complex) is a key component of the limbic system located in the temporal lobe [1]. It processes emotions like fear and aggression [1]. ### **Explanation of the Correct Answer** The **stria terminalis** is the primary efferent (outflow) pathway of the amygdala. It arises from the corticomedial group of amygdaloid nuclei and follows a C-shaped course along the lateral border of the thalamus, ending mainly in the **hypothalamus** (specifically the ventromedial nucleus) and the septal area [1]. *Note:* The other major efferent pathway is the **ventral amygdalofugal pathway**, which projects to the thalamus and prefrontal cortex. ### **Explanation of Incorrect Options** * **B. Stria vascularis:** This is a specialized vascular tissue located in the lateral wall of the **cochlear duct** (inner ear) responsible for producing endolymph. * **C. Lamina terminalis:** This is a thin layer of gray matter that forms the anterior wall of the **third ventricle**. It represents the site of closure of the cranial neuropore. * **D. Mossy fibers:** These are afferent (input) fibers to the **cerebellum** (originating from the spinal cord and pontine nuclei) and are also found in the **hippocampus** (axons of granule cells). ### **High-Yield Clinical Pearls for NEET-PG** * **Klüver-Bucy Syndrome:** Bilateral destruction of the amygdala (often due to HSV encephalitis) leads to hyperorality, hypersexuality, visual agnosia, and docility (loss of fear). * **Anatomical Landmark:** The stria terminalis runs in the groove between the **thalamus** and the **caudate nucleus**, accompanied by the **thalamostriate vein**. * **Input vs. Output:** While the stria terminalis is the main output, the **stria medullaris** (often confused) connects the septal nuclei to the habenular nuclei [1].

Q: Which of the following nerves is NOT involved in swallowing?

Vestibulocochlear nerve. **Explanation:** Swallowing (deglutition) is a complex physiological process involving a coordinated sequence of events across the oral, pharyngeal, and esophageal stages. It requires the integration of multiple cranial nerves (CN V, VII, IX, X, and XII). **Why Option A is Correct:** The **Vestibulocochlear nerve (CN VIII)** is purely a special sensory nerve responsible for hearing (cochlear division) and equilibrium/balance (vestibular division). It has no motor or sensory role in the mechanics of swallowing or the protection of the airway during the bolus transit. **Why the other options are incorrect:** * **Trigeminal nerve (CN V):** Involved in the **oral preparatory stage**. The mandibular branch (V3) supplies the muscles of mastication and the tensor veli palatini (which tenses the soft palate). * **Facial nerve (CN VII):** Essential for the **oral stage**. It supplies the buccinator (prevents food from pocketing in the vestibule), the orbicularis oris (maintains oral seal), and the stylohyoid/digastric muscles which assist in hyoid elevation. * **Hypoglossal nerve (CN XII):** Critical for **bolus formation and transport**. It supplies all intrinsic and extrinsic muscles of the tongue (except palatoglossus), allowing the tongue to push the bolus into the pharynx. **NEET-PG High-Yield Pearls:** * **The "Swallowing Center":** Located in the **Medulla Oblongata** (Nucleus Tractus Solitarius and Nucleus Ambiguus). * **Glossopharyngeal (CN IX) & Vagus (CN X):** These are the primary nerves for the **pharyngeal stage**. CN IX provides sensory input for the gag reflex, while CN X (via the Recurrent Laryngeal Nerve) ensures airway protection by closing the vocal cords. * **Muscle Exception:** The **Palatoglossus** is the only tongue muscle NOT supplied by CN XII; it is supplied by the **Vagus nerve (CN X)** via the pharyngeal plexus.

Q: A lesion of the ventrolateral part of the spinal cord will lead to loss (below the level of the lesion) of which sensation?

Pain sensation on the contralateral side. ### Explanation The **ventrolateral (anterolateral) part** of the spinal cord contains the **Lateral Spinothalamic Tract (LSTT)** [1]. This tract is responsible for carrying sensations of **pain and temperature** [2]. **1. Why Option C is Correct:** The first-order neurons of the LSTT enter the spinal cord and synapse in the dorsal horn (Substantia Gelatinosa). The second-order neurons then **decussate (cross over)** to the opposite side via the anterior white commissure within 1–2 spinal segments before ascending in the ventrolateral column [2]. Therefore, a lesion in the ventrolateral part of the spinal cord interrupts fibers that have already crossed, leading to a loss of pain and temperature sensation on the **contralateral (opposite) side**, starting 1–2 segments below the level of the lesion [1]. **2. Why Other Options are Incorrect:** * **Options B & D (Proprioception):** Proprioception, vibration, and fine touch are carried by the **Dorsal Columns** (Fasciculus Gracilis and Cuneatus), located in the posterior part of the spinal cord, not the ventrolateral part [2]. * **Option A (Ipsilateral Pain):** Because the LSTT decussates almost immediately upon entering the cord, pain loss is always contralateral to the lesion [2]. Ipsilateral loss would only occur if the dorsal root or the dorsal horn itself were damaged at that specific level. **3. Clinical Pearls for NEET-PG:** * **Brown-Séquard Syndrome:** A hemisection of the spinal cord results in **ipsilateral** loss of proprioception/motor function and **contralateral** loss of pain/temperature. * **Syringomyelia:** Characterized by a "cape-like" bilateral loss of pain and temperature because the expanding syrinx destroys the crossing fibers in the **anterior white commissure**. * **Somatotopic Arrangement:** In the LSTT, fibers from the sacral region are most lateral, while cervical fibers are most medial [2].

Q: Which of the following cranial nerves does not contain parasympathetic motor (GVE) fibers?

VI. **Explanation:** The parasympathetic nervous system (craniosacral outflow) involves four specific cranial nerves that carry **General Visceral Efferent (GVE)** fibers to various ganglia in the head and neck [1]. These are **CN III, VII, IX, and X**. **1. Why VI is the correct answer:** The **Abducens nerve (CN VI)** is a purely somatic motor nerve. Its only function is to provide General Somatic Efferent (GSE) innervation to the **Lateral Rectus** muscle of the eye. It does not possess any autonomic (parasympathetic) nuclei or fibers. **2. Why the other options are incorrect:** * **CN III (Oculomotor):** Carries preganglionic parasympathetic fibers from the **Edinger-Westphal nucleus** to the ciliary ganglion. These fibers control the sphincter pupillae (miosis) and ciliary muscles (accommodation). * **CN IX (Glossopharyngeal):** Carries fibers from the **Inferior Salivatory nucleus** via the lesser petrosal nerve to the otic ganglion, providing secretomotor supply to the **parotid gland**. * **CN X (Vagus):** Carries fibers from the **Dorsal Nucleus of Vagus** to provide extensive parasympathetic innervation to the thoracic and abdominal viscera (up to the splenic flexure). **High-Yield NEET-PG Pearls:** * **Mnemonic for Parasympathetic CNs:** "3, 7, 9, 10" (or 1973). * **CN VII (Facial):** Often tested; it carries fibers from the **Superior Salivatory nucleus** to the submandibular and pterygopalatine ganglia (supplying lacrimal, submandibular, and sublingual glands). * **Purely Motor Nerves:** CN IV, VI, XI, and XII carry only motor fibers (GSE/SVE) and no parasympathetic components.

Q: Amacrine cells are found in which part of the eye?

Retina. ### Explanation **Correct Answer: B. Retina** **Medical Concept:** Amacrine cells are specialized **interneurons** located in the **Inner Nuclear Layer (INL)** of the retina [1]. They are unique because they lack traditional axons (the name "amacrine" means "no long fiber"). Their primary role is to modulate the transmission of visual signals between bipolar cells and ganglion cells [2]. They facilitate lateral inhibition and temporal processing, helping the eye detect motion and adjust to changes in illumination. **Analysis of Incorrect Options:** * **A. Cornea:** The cornea is the transparent, avascular anterior part of the eye. It consists of five layers (Epithelium, Bowman’s, Stroma, Descemet’s, and Endothelium) but contains no neuronal cell bodies like amacrine cells [1]. * **C. Lens:** The lens is a crystalline, biconvex structure responsible for accommodation [1]. It is composed of lens fibers and an anterior epithelium; it lacks neural circuitry. * **D. Iris:** The iris is part of the uveal tract (vascular tunic). It contains pigment cells and smooth muscles (sphincter and dilator pupillae) to regulate pupil size, but not retinal interneurons. **High-Yield Facts for NEET-PG:** * **Retinal Layers:** Amacrine cells have their cell bodies in the **Inner Nuclear Layer** and their processes in the **Inner Plexiform Layer** [1]. * **Neurotransmitters:** Most amacrine cells are inhibitory, utilizing **GABA or Glycine**. * **Horizontal Cells vs. Amacrine Cells:** While both are interneurons, Horizontal cells mediate lateral inhibition between photoreceptors and bipolar cells (Outer Plexiform Layer), whereas Amacrine cells act between bipolar and ganglion cells (Inner Plexiform Layer) [2]. * **Müller Cells:** These are the principal glial cells of the retina, spanning almost its entire thickness.

Q: The stria of Gennari is a histological feature of which area?

Visual area. The **Stria of Gennari** is a distinct white line visible to the naked eye in the gray matter of the **primary visual cortex (Brodmann area 17)**, located in the occipital lobe along the calcarine fissure [1]. 1. **Why the Visual Area is Correct:** Histologically, the cerebral cortex consists of six layers. In the primary visual cortex, the **internal granular layer (Layer IV)** is exceptionally thick and contains a dense band of myelinated horizontal fibers [1]. This prominent band is the Stria of Gennari. Because of this feature, the primary visual cortex is also known as the **"Striate Cortex"** [1]. 2. **Why the Other Options are Incorrect:** * **Motor speech area (Broca’s area, 44, 45):** Located in the inferior frontal gyrus. It is characterized by motor output functions and lacks the specialized sensory stria. * **Auditory area (41, 42):** Located in the superior temporal gyrus (Heschl’s gyri). While it is a sensory area, it does not possess the macroscopically visible Stria of Gennari. * **Prefrontal area:** Involved in executive functions and personality; it is a granular cortex but lacks this specific myelinated landmark. **NEET-PG High-Yield Pearls:** * **Location:** Area 17 is found in the walls of the **calcarine sulcus** [1]. * **Blood Supply:** Primarily by the **posterior cerebral artery**. However, the macular representation at the occipital pole has a dual supply from both the **middle and posterior cerebral arteries**, explaining "macular sparing" in certain strokes. * **Gennari vs. Baillarger:** The Stria of Gennari is actually a specifically enlarged **outer band of Baillarger**.

Q: Which of the following arteries does NOT give rise to arteries supplying the spinal cord?

Thoracoacromial artery. The spinal cord is supplied by a longitudinal system (one anterior and two posterior spinal arteries) and a segmental system (radicular and segmental medullary arteries). The segmental supply is crucial as the longitudinal arteries are often insufficient to supply the entire length of the cord. **Explanation of the Correct Answer:** **D. Thoracoacromial artery:** This is a branch of the second part of the **axillary artery**. It supplies the pectoral muscles, deltoid, acromion, and clavicular region. It is located too laterally and superficially in the thoracic wall to contribute to the spinal cord's blood supply. **Explanation of Incorrect Options:** * **A. Ascending cervical artery:** A branch of the thyrocervical trunk (subclavian artery), it provides segmental branches to the **cervical** spinal cord. * **B. Deep cervical artery:** Arising from the costocervical trunk (subclavian artery), it supplies the **lower cervical** and upper thoracic segments of the cord. * **C. Intercostal arteries:** Posterior intercostal arteries (branches of the thoracic aorta) give off spinal branches that enter the intervertebral foramina to supply the **thoracic** spinal cord [1]. **High-Yield NEET-PG Pearls:** 1. **Artery of Adamkiewicz (Arteria Radicularis Magna):** The largest segmental medullary artery, usually arising from a left-sided lower intercostal or upper lumbar artery (T9–L2). It is the major source of blood to the lower two-thirds of the spinal cord. 2. **Watershed Areas:** The mid-thoracic region (T4–T8) is a "watershed" area with relatively poor collateral circulation, making it highly susceptible to ischemic injury during aortic surgery or hypotension. 3. **Origin Summary:** Spinal supply originates from the **Vertebral, Ascending Cervical, Deep Cervical, Intercostal, Lumbar, and Lateral Sacral arteries.** [1]

Q: Which is the smallest cranial nerve?

Trochlear. The **Trochlear nerve (CN IV)** is identified as the smallest cranial nerve based on the **number of axons** it contains (approximately 2,400–3,400). Despite its small size, it holds several unique anatomical distinctions: it is the only cranial nerve to emerge from the **dorsal (posterior) aspect** of the brainstem, and it has the **longest intracranial course** as it winds around the brainstem to reach the orbit. **Analysis of Options:** * **Olfactory (CN I):** While these are short nerve filaments, they consist of numerous bundles passing through the cribriform plate, making them collectively larger in axonal volume than CN IV. * **Oculomotor (CN III):** This is a significantly larger motor nerve that supplies four of the six extraocular muscles, the levator palpebrae superioris, and carries parasympathetic fibers. * **Accessory (CN XI):** This nerve has a substantial spinal component and a cranial component, supplying large muscles like the Trapezius and Sternocleidomastoid; it is much thicker than the Trochlear nerve. **NEET-PG High-Yield Pearls:** * **Smallest Nerve:** Trochlear (CN IV). * **Largest Nerve:** Trigeminal (CN V) – based on overall girth/thickness. * **Longest Nerve:** Vagus (CN X) – based on its course from the head to the abdomen. * **Longest Intracranial Course:** Trochlear (CN IV). * **Most Fragile/Commonly Injured in Head Trauma:** Trochlear (CN IV) due to its long, thin course. * **Clinical Sign:** CN IV palsy presents with **vertical diplopia** (worse when looking down, e.g., walking downstairs) and a compensatory **head tilt** to the opposite side.

Q: Which is the longest cranial nerve?

Vagus. ### Explanation **Correct Option: D (Vagus Nerve)** The **Vagus Nerve (CN X)** is the longest cranial nerve in the body. Its name is derived from the Latin word *vagus*, meaning "wandering." Unlike other cranial nerves that are primarily restricted to the head and neck, the Vagus nerve descends through the carotid sheath into the thorax and continues into the abdomen [1]. It provides extensive parasympathetic innervation to visceral organs, extending as far as the splenic flexure of the large intestine [1]. **Analysis of Incorrect Options:** * **A. Optic Nerve (CN II):** This is a relatively short sensory nerve. It is unique because it is embryologically an outgrowth of the forebrain (diencephalon) and is covered by all three layers of meninges [2]. * **B. Abducent Nerve (CN VI):** This nerve has the **longest intracranial course** (specifically the longest subarachnoid course), making it highly susceptible to injury in cases of increased intracranial pressure (ICP). However, its total length is much shorter than the Vagus. * **C. Trigeminal Nerve (CN V):** This is the **largest** cranial nerve in terms of diameter and sensory distribution to the face, but it is not the longest. **High-Yield Clinical Pearls for NEET-PG:** * **Longest Cranial Nerve:** Vagus Nerve (CN X). * **Longest Intracranial Course:** Abducent Nerve (CN VI). * **Smallest/Slenderest Cranial Nerve:** Trochlear Nerve (CN IV). * **Only Cranial Nerve to emerge from the posterior aspect of the brainstem:** Trochlear Nerve (CN IV). * **Vagus Nerve Exit:** It exits the skull through the **Jugular Foramen** along with CN IX and CN XI.

Question 1

A 55-year-old hypertensive female presented with left-sided weakness and left-sided homonymous hemianopsia. The symptoms developed slowly over a few years. MRI Brain shows a lesion affecting a structure that causes weakness. Which nuclei are most closely related to this structure?

Accepted Answer

Red nucleus and Substantia nigra

Answer

Red nucleus and Dentate nucleus

Answer

Red nucleus, Dentate nucleus, and Substantia nigra

Answer

All of the above

Question 2

Which of the following represents the efferent fibers of the amygdala?

Accepted Answer

Stria terminalis

Answer

Striavascularis

Answer

Lamina terminalis

Answer

Mossy fibers

Question 3

Which of the following nerves is NOT involved in swallowing?

Accepted Answer

Vestibulocochlear nerve

Answer

Facial nerve

Answer

Trigeminal nerve

Answer

Hypoglossal nerve

Question 4

A lesion of the ventrolateral part of the spinal cord will lead to loss (below the level of the lesion) of which sensation?

Accepted Answer

Pain sensation on the contralateral side

Answer

Pain sensation on the ipsilateral side

Answer

Proprioception on the contralateral side

Answer

Proprioception on the ipsilateral side

Question 5

Which of the following cranial nerves does not contain parasympathetic motor (GVE) fibers?

Accepted Answer

VI

Answer

III

Answer

IX

Answer

X

Question 6

Amacrine cells are found in which part of the eye?

Accepted Answer

Retina

Answer

Cornea

Answer

Lens

Answer

Iris

Question 7

The stria of Gennari is a histological feature of which area?

Accepted Answer

Visual area

Answer

Motor speech area

Answer

Auditory area

Answer

Prefrontal area

Question 8

Which of the following arteries does NOT give rise to arteries supplying the spinal cord?

Accepted Answer

Thoracoacromial artery

Answer

Ascending cervical artery

Answer

Deep cervical artery

Answer

Intercostal arteries

Question 9

Which is the smallest cranial nerve?

Accepted Answer

Trochlear

Answer

Olfactory

Answer

Oculomotor

Answer

Accessory

Question 10

Which is the longest cranial nerve?

Accepted Answer

Vagus

Answer

Optic

Answer

Abducent

Answer

Trigeminal

Neuroanatomy — MCQs

Neuroanatomy — MCQs

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