Neuroanatomy — MCQs
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In which part of the inner ear are cristae located?
Third order neurons of sensations from face arise in?
Which somatic efferent nerve arises from the medulla?
Which of the following cranial nerves is primarily responsible for taste sensation from the posterior one-third of the tongue?
Which artery supplies the paracentral lobule?
Which of the following nuclei belong to the general visceral afferent column?
Which nerve is the Chorda tympani a branch of?
All of the following are main branches of the Trigeminal nerve except which of the following?
Which arteries form the anterior spinal artery?
Weakness of extensor Hallucis longus is due to which nerve root mainly?
Neuroanatomy Indian Medical PG Practice Questions and MCQs
Question 1701: In which part of the inner ear are cristae located?
- A. Utricle
- B. Saccule
- C. Otolith membrane
- D. Semicircular canals (ampullae) (Correct Answer)
Explanation: - **Cristae ampullares** are sensory organs found within the **ampullae** of the semicircular canals [1]. - They are responsible for detecting **angular acceleration** (rotational movements) of the head [1]. *Utricle* - The utricle contains **maculae**, not cristae, which detect **linear acceleration** and the position of the head relative to gravity [1]. - Its sensory hair cells are covered by an **otolithic membrane** [1]. *Saccule* - Similar to the utricle, the saccule also contains **maculae** for detecting **linear acceleration** and vertical head movements [1]. - It plays a role in sensing gravity and vertical motion [1]. *Otolith membrane* - The **otolith membrane** is a gel-like structure embedded with **otoliths (calcium carbonate crystals)** that overlie the hair cells in the maculae of the utricle and saccule [1]. - This membrane is not a location for cristae, but rather a component of the sensory mechanism for **linear acceleration** and gravity.
Question 1702: Third order neurons of sensations from face arise in?
- A. Medulla
- B. Spinal nucleus of trigeminal
- C. Thalamus (Correct Answer)
- D. Brainstem
Explanation: The thalamus serves as a crucial relay station for almost all sensory information before it reaches the cerebral cortex for conscious perception [1]. For facial sensations, the third-order neurons are located in the ventral posterior medial (VPM) nucleus of the thalamus. The medulla primarily contains the second-order neurons of the trigeminal pathway, specifically in the spinal trigeminal nucleus for pain and temperature from the face. It does not house the third-order neurons that project to the cortex. The spinal nucleus of the trigeminal nerve processes sensations of pain and temperature from the face, acting as the location for the second-order neurons [2]. It relays this information to the contralateral thalamus, not originating the third-order neurons [2]. The brainstem is a broader region that includes the midbrain, pons, and medulla, and contains various nuclei involved in sensory pathways. While it houses first and second-order neurons for facial sensation, the third-order neurons, which project to the cortex, are located in the thalamus, anatomically distinct from the main brainstem structures.
Question 1703: Which somatic efferent nerve arises from the medulla?
- A. Oculomotor nerve
- B. Trochlear nerve
- C. Abducent nerve
- D. Hypoglossal nerve (Correct Answer)
Explanation: ***Hypoglossal nerve*** - The **hypoglossal nerve (CN XII)** is a somatic efferent nerve that controls the majority of the **intrinsic and extrinsic muscles of the tongue**. [2] - Its nucleus is located in the **medulla oblongata**, from where its fibers emerge from the anterolateral sulcus. [2] *Oculomotor nerve* - The **oculomotor nerve (CN III)** emerges from the **midbrain**, not the medulla. [1] - It controls most extraocular muscles, the pupillary constrictor, and the ciliary muscle. [1] *Trochlear nerve* - The **trochlear nerve (CN IV)** is the only cranial nerve that emerges from the **dorsal aspect of the midbrain**, not the medulla. - It innervates the **superior oblique muscle** of the eye. *Abducent nerve* - The **abducent nerve (CN VI)** has its nucleus in the **pons**, and emerges at the **pontomedullary junction** (the junction between pons and medulla). - It innervates the **lateral rectus muscle** of the eye.
Question 1704: Which of the following cranial nerves is primarily responsible for taste sensation from the posterior one-third of the tongue?
- A. Glossopharyngeal nerve (Correct Answer)
- B. Facial nerve
- C. Vagus nerve
- D. Hypoglossal nerve
Explanation: No changes were made to the original explanation because the provided references did not meet the relevance criteria for the specific question regarding the glossopharyngeal nerve and taste sensation from the posterior tongue.
Question 1705: Which artery supplies the paracentral lobule?
- A. Medial Striate artery
- B. Calloso Marginal artery (Correct Answer)
- C. Pericallosal artery
- D. Frontopolar artery
Explanation: ***Callosomarginal artery*** - The **callosomarginal artery** is a major branch of the **anterior cerebral artery (ACA)** that runs in the **cingulate sulcus** (callosomarginal sulcus). - It is the **primary arterial supply** to the **paracentral lobule**, which contains the motor and sensory cortex for the **lower limb and perineum**. - This artery gives cortical branches that directly perfuse the paracentral lobule region. *Medial Striate artery* - Also known as the **recurrent artery of Heubner**, this vessel supplies deep structures including portions of the **internal capsule**, **caudate nucleus**, and **putamen**. - It is a branch of the ACA but supplies **subcortical structures**, not cortical areas like the paracentral lobule. *Pericallosal artery* - This is the **terminal continuation** of the anterior cerebral artery that runs along the superior surface of the **corpus callosum**. - While it does give **some cortical branches** to the medial hemisphere including regions near the paracentral lobule, the **callosomarginal artery** is considered the **primary and more direct supply** to the paracentral lobule itself. - In cases where the callosomarginal artery is small or absent (anatomical variation), the pericallosal artery may provide compensatory supply. *Frontopolar artery* - This branch of the **anterior cerebral artery** supplies the **frontal pole** and **medial/orbital surfaces of the frontal lobe**. - Its territory is **anterior** to the paracentral lobule, which is located more posteriorly at the junction of the frontal and parietal lobes on the medial hemisphere.
Question 1706: Which of the following nuclei belong to the general visceral afferent column?
- A. Nucleus of the solitary tract (Correct Answer)
- B. Facial nerve nucleus
- C. Trigeminal nucleus
- D. Nucleus ambiguus
Explanation: The nucleus of the solitary tract (nucleus solitarius) is the primary general visceral afferent (GVA) nucleus in the brainstem. It receives visceral sensory information from cranial nerves VII (facial), IX (glossopharyngeal), and X (vagus) regarding taste, chemoreception, and mechanoreception from thoracic and abdominal viscera [1]. This nucleus processes sensory input from the gastrointestinal tract, respiratory system, cardiovascular system, and carotid body/sinus baroreceptors and chemoreceptors [2]. It plays a crucial role in autonomic reflexes including cardiovascular, respiratory, and digestive regulation. *Facial nerve nucleus* - The facial nerve nucleus is a special visceral efferent (branchial motor) nucleus controlling the muscles of facial expression. - It does not process general visceral afferent information. *Trigeminal nucleus* - The trigeminal nucleus is a general somatic afferent (GSA) nucleus processing sensation from the face, oral cavity, and anterior two-thirds of the head. - It handles touch, pain, temperature, and proprioception from somatic structures, not visceral sensory information. *Nucleus ambiguus* - The nucleus ambiguus is a special visceral efferent (branchial motor) nucleus controlling muscles of the pharynx, larynx, and upper esophagus via cranial nerves IX, X, and XI. - Its function is purely motor, not sensory or afferent.
Question 1707: Which nerve is the Chorda tympani a branch of?
- A. Facial nerve (Correct Answer)
- B. Trigeminal nerve
- C. Greater auricular nerve
- D. External laryngeal nerve
Explanation: **Facial nerve** - The **chorda tympani** is a branch of the **facial nerve (cranial nerve VII)** that separates from the main trunk within the temporal bone. - It carries **taste sensations** from the anterior two-thirds of the tongue and provides **parasympathetic innervation** to the submandibular and sublingual glands. *Trigeminal nerve* - The **trigeminal nerve (cranial nerve V)** is primarily responsible for **sensory innervation** to the face and motor innervation to the muscles of mastication. - While it has a role in sensation from the tongue (lingual nerve, a branch of the mandibular division), it does not directly give rise to the chorda tympani. *Greater auricular nerve* - The **greater auricular nerve** is a branch of the **cervical plexus** (C2-C3). - It provides **sensory innervation** to the skin over the parotid gland, the mastoid process, and parts of the auricle, with no connection to taste or salivary gland function. *External laryngeal nerve* - The **external laryngeal nerve** is a branch of the **superior laryngeal nerve**, which itself is a branch of the **vagus nerve (cranial nerve X)**. - It primarily innervates the **cricothyroid muscle** of the larynx, responsible for phonation, and has no association with the chorda tympani.
Question 1708: All of the following are main branches of the Trigeminal nerve except which of the following?
- A. Maxillary nerve
- B. Ophthalmic nerve
- C. Facial nerve (Correct Answer)
- D. Mandibular nerve
Explanation: ***Facial nerve*** - The **facial nerve (cranial nerve VII)** is a distinct cranial nerve responsible primarily for **facial expression**, taste sensation, and parasympathetic innervation to several glands. - It is **not a branch of the trigeminal nerve**; they are separate cranial nerves with different origins and functions. *Mandibular nerve* - The **mandibular nerve (V3)** is one of the three main divisions of the trigeminal nerve, providing **sensory innervation** to the lower face and masticatory motor function. - It is a **mixed nerve** containing both sensory and motor fibers, unlike V1 and V2 which are purely sensory. *Maxillary nerve* - The **maxillary nerve (V2)** is one of the three main divisions of the trigeminal nerve, carrying **sensory information** from the middle part of the face, maxillary teeth, and nasal cavity. - It is a **purely sensory branch** of the trigeminal nerve. *Ophthalmic nerve* - The **ophthalmic nerve (V1)** is one of the three main divisions of the trigeminal nerve, responsible for **sensory innervation** to the forehead, upper eyelid, and eyeball. - It is also a **purely sensory branch** of the trigeminal nerve.
Question 1709: Which arteries form the anterior spinal artery?
- A. Radicular arteries
- B. Intercostal arteries
- C. Segmental arteries
- D. Vertebral arteries (Correct Answer)
Explanation: ***Vertebral arteries*** - The **anterior spinal artery** is formed by the fusion of two small branches that arise from each **vertebral artery** near their junction to form the **basilar artery**. - These two branches descend anteriorly to unite into a single vessel that runs the length of the spinal cord. *Radicular arteries* - **Radicular arteries** are branches of the segmental arteries that supply the nerve roots and meninges, but do not contribute directly to the formation of the main anterior spinal artery. - While they do supply the spinal cord, they are not the primary source for the *formation* of the anterior spinal artery itself. *Segmental arteries* - **Segmental arteries** (e.g., intercostal, lumbar, and sacral arteries) give rise to the radicular and medullary arteries that reinforce the anterior and posterior spinal arteries along their course. - They *reinforce* the spinal arteries but do not **form** the anterior spinal artery initially. *Intercostal arteries* - **Intercostal arteries** are examples of segmental arteries that supply the thoracic region. - They give rise to contributing **radiculomedullary arteries**, but are not involved in the initial formation of the anterior spinal artery, which occurs cranially.
Question 1710: Weakness of extensor Hallucis longus is due to which nerve root mainly?
- A. L5 (Correct Answer)
- B. L4
- C. S1
- D. S2
Explanation: ***L5*** - The **extensor hallucis longus** muscle, primarily responsible for **dorsiflexion of the great toe**, is predominantly innervated by the **L5 nerve root** via the deep fibular nerve. - Weakness in this muscle is a classic sign of **L5 radiculopathy**. - L5 radiculopathy typically presents with **foot drop** (due to tibialis anterior weakness), **great toe extensor weakness**, and sensory loss over the dorsum of the foot. *L4* - The **L4 nerve root** primarily innervates the **quadriceps** muscles and contributes to the **tibialis anterior**. - Weakness in **knee extension** and diminished **patellar reflex** are more indicative of L4 radiculopathy. - L4 lesions do not typically cause isolated extensor hallucis longus weakness. *S1* - The **S1 nerve root** primarily innervates the **gastrocnemius and soleus** muscles. - Weakness in **plantarflexion** and loss of the **Achilles reflex** are characteristic of S1 radiculopathy. - S1 radiculopathy presents with difficulty walking on toes, not great toe dorsiflexion weakness. *S2* - The **S2 nerve root** contributes to the innervation of the **hamstrings** and intrinsic foot muscles. - Involvement of S2 would typically manifest as weakness in **knee flexion** and sensory changes in the posterior thigh and perineum. - S2 does not innervate the extensor hallucis longus.
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