Neuroanatomy — MCQs

Neuroanatomy Indian Medical PG Practice Questions and MCQs

Question 1751: After trauma, a person cannot move their eye outward beyond the midpoint. Which nerve is injured?

A. 3rd
B. 4th
C. 6th (Correct Answer)
D. 2nd

Explanation: ***6th*** - The **abducens nerve (CN VI)** innervates the **lateral rectus muscle**, which is responsible for moving the eye **outward (abduction)** [1]. - Injury to the abducens nerve would result in an inability to move the eye laterally, causing an **esotropia** (eye turned inward at rest) [1]. *2nd* - The **optic nerve (CN II)** is responsible for **vision**, not eye movement [2]. - Damage to this nerve would cause **visual field defects** or **blindness** [3]. *3rd* - The **oculomotor nerve (CN III)** controls most extraocular muscles, including the **medial, superior, and inferior rectus** and **inferior oblique muscles**, as well as the **levator palpebrae superioris** and **pupillary constriction** [2]. - Injury to CN III would lead to a **down and out deviation of the eye**, **ptosis**, and a **dilated pupil** [2]. *4th* - The **trochlear nerve (CN IV)** innervates the **superior oblique muscle**, which primarily causes **intorsion** (rotation downward and inward) [1]. - Damage to this nerve results in **vertical diplopia**, especially when looking down and in, and a characteristic **head tilt** to compensate [3].

Question 1752: What is true about chorda tympani?

A. Postganglionic sympathetic
B. Preganglionic sympathetic
C. Preganglionic parasympathetic (Correct Answer)
D. Postganglionic parasympathetic

Explanation: ***Preganglionic parasympathetic*** - The **chorda tympani** carries preganglionic parasympathetic fibers that originate from the **facial nerve (CN VII)** nucleus. - These fibers provide secretomotor innervation to the **submandibular** and **sublingual salivary glands** after synapsing in the submandibular ganglion. *Postganglionic sympathetic* - **Postganglionic sympathetic** fibers usually arise from paravertebral or prevertebral ganglia and innervate target organs directly. [1] - The chorda tympani is part of the parasympathetic nervous system, not the sympathetic. *Preganglionic sympathetic* - **Preganglionic sympathetic** fibers originate in the intermediolateral cell column of the spinal cord and synapse in sympathetic ganglia. [1] - The chorda tympani is associated with cranial nerves and the parasympathetic system rather than the sympathetic trunk. *Postganglionic parasympathetic* - **Postganglionic parasympathetic** fibers emerge from ganglia like the submandibular ganglion after synapsing with preganglionic fibers. - The chorda tympani itself contains the **preganglionic** fibers that *lead to* such ganglia, it does not contain postganglionic fibers.

Question 1753: All the following are characteristics of the oculomotor nerve except:

A. Carries parasympathetic nerve fibres
B. Supplies inferior oblique muscle
C. Enters orbit through the inferior orbital fissure (Correct Answer)
D. Enters orbit through the superior orbital fissure

Explanation: ***Enters orbit through the inferior orbital fissure*** - The oculomotor nerve **does not** enter the orbit through the **inferior orbital fissure**; it enters via the **superior orbital fissure**. - The **inferior orbital fissure** transmits structures like the **maxillary nerve (V2)**, **zygomatic nerve**, and **inferior ophthalmic vein**. *Carries parasympathetic nerve fibres* - The oculomotor nerve contains **parasympathetic preganglionic fibers** that synapse in the **ciliary ganglion** [1]. - These fibers control **pupillary constriction** (via the **sphincter pupillae**) and **accommodation** (via the **ciliary muscle**) [1]. *Supplies inferior oblique muscle* - The **inferior oblique muscle** is one of the **extraocular muscles** innervated by the **oculomotor nerve (CN III)** [2]. - This muscle works to **elevate** and **externally rotate** the eye [2]. *Enters orbit through the superior orbital fissure* - The oculomotor nerve indeed passes through the **superior orbital fissure** to enter the orbit. - This fissure serves as the passage for several cranial nerves and vessels, including the **oculomotor (III)**, **trochlear (IV)**, **abducens (VI)**, and branches of the **ophthalmic nerve (V1)**.

Question 1754: Which of the following structures is located within the cavernous sinus?

A. Maxillary division of V nerve
B. Mandibular division of V nerve
C. Internal carotid artery (Correct Answer)
D. Facial nerve

Explanation: ***Internal carotid artery*** - The **internal carotid artery** passes **through the lumen** of the cavernous sinus, which is a dural venous sinus located on either side of the sella turcica. - Along with the **abducens nerve (CN VI)**, the internal carotid artery is one of only two structures that passes directly through the cavernous sinus cavity itself. - This is the **most accurate answer** as it traverses the actual sinus space, not just the wall. *Maxillary division of V nerve* - The **maxillary division of the trigeminal nerve (V2)** runs within the **lateral wall** of the cavernous sinus, not through its lumen. - While technically "within" the sinus structure, it is embedded in the dural wall rather than passing through the blood-filled cavity. - This nerve exits the skull through the **foramen rotundum**. - Other nerves in the lateral wall include **CN III, CN IV, and V1**. *Mandibular division of V nerve* - The **mandibular division of the trigeminal nerve (V3)** does not pass through or near the cavernous sinus. - It exits the middle cranial fossa directly via the **foramen ovale**, positioned inferior and separate from the cavernous sinus. - V3 is the only division of the trigeminal nerve that does not have any relationship with the cavernous sinus. *Facial nerve* - The **facial nerve (CN VII)** has no anatomical relationship with the cavernous sinus. - It enters the temporal bone through the **internal acoustic meatus**, travels through the facial canal, and exits via the **stylomastoid foramen**. - Its course is entirely separate from the cavernous sinus region.

Question 1755: Which of the following statements about the location of the otic ganglion is correct?

A. Anterior to middle meningeal artery
B. Lateral to mandibular nerve
C. Inferior to foramen ovale (Correct Answer)
D. Lateral to tensor veli palatini

Explanation: ***Inferior to foramen ovale*** - The **otic ganglion** is a small parasympathetic ganglion located in the **infratemporal fossa**. - It is consistently found just **inferior to the foramen ovale**, often within the fossa medial to the mandibular nerve. *Lateral to tensor veli palatini* - The otic ganglion is actually located **medial** (or superficial) to the origin of the **tensor veli palatini muscle**. - Its position is more closely associated with the medial pterygoid muscle and the Eustachian tube. *Lateral to mandibular nerve* - The otic ganglion is typically situated **medial** to the **mandibular nerve (V3)**, specifically medial to its main trunk or branches near the foramen ovale. - It is closely applied to the medial aspect of the mandibular nerve. *Anterior to middle meningeal artery* - The **middle meningeal artery** typically passes **lateral** to the otic ganglion as it ascends through the foramen spinosum. - Therefore, the ganglion is generally located **medial** or posterior to the artery, not anterior.

Question 1756: Which type of neurons are found in sympathetic ganglia?

A. Pseudounipolar
B. Multipolar (Correct Answer)
C. Unipolar
D. Bipolar

Explanation: ***Multipolar*** - **Multipolar neurons** are the most common type of neurons in the central nervous system and are present in **autonomic ganglia**, including sympathetic ganglia [2, 4]. - They are characterized by having **one axon** and **multiple dendrites**, allowing for the integration of signals from many sources [2]. *Unipolar* - **Unipolar neurons** have a single process extending from the cell body that then branches into another direction; they are rare in vertebrates [1]. - They are primarily found in **invertebrates**, serving sensory functions. *Bipolar* - **Bipolar neurons** have two processes extending from the cell body: one axon and one dendrite [2]. - They are typically found in specialized sensory organs such as the **retina of the eye** and the **olfactory epithelium** [2]. *Pseudounipolar* - **Pseudounipolar neurons** develop from bipolar neurons, but their two processes fuse into a single short process that then divides into two branches: an axon and a dendrite [2]. - These neurons are characteristic of the **dorsal root ganglia** and function as **sensory neurons**, transmitting information from the periphery to the central nervous system [2].

Question 1757: Between which structures is the hypothalamus placed in the Papez circuit of the limbic system based on its function?

A. Mammillary bodies-cingulate cortex
B. Cingulate cortex-hippocampus
C. Hippocampus-thalamus (Correct Answer)
D. Thalamus-cingulate cortex

Explanation: ***Hippocampus-thalamus*** - In the Papez circuit, the **hypothalamus** receives input from the **hippocampus** (via the fornix) [1] and projects to the **thalamus** (specifically the anterior thalamic nuclei) via the mammillary bodies [2]. - This position highlights its role in integrating **emotional responses** [3] and **memory formation** [1]. *Cingulate cortex-hippocampus* - The **cingulate cortex** projects to the **hippocampus**, but the hypothalamus is not directly positioned between these two structures. - The pathway from the cingulate cortex to the hippocampus is a separate part of the circuit, involving other intermediate structures. *Mammillary bodies-cingulate cortex* - The **mammillary bodies** are part of the hypothalamus and project to the anterior **thalamic nuclei** [2], which then project to the **cingulate cortex**. - The hypothalamus itself is not positioned *between* the mammillary bodies and the cingulate cortex; rather, the mammillary bodies are a component through which the hypothalamus influences the cingulate. *Thalamus-cingulate cortex* - The **thalamus** (anterior nuclei) [2] projects directly to the **cingulate cortex** in the Papez circuit. - The hypothalamus is involved indirectly, as it projects to the thalamus, but it is not situated as an intermediary *between* the thalamus and the cingulate cortex.

Question 1758: Which of the following statements is true about the 3rd ventricle?

A. Cavity of the rhombencephalon
B. Communicates with the 4th ventricle via the aqueduct of Sylvius (Correct Answer)
C. Communicates exclusively with the lateral ventricles via the foramen of Monro
D. Interthalamic adhesions connect the lateral walls of the 3rd ventricle

Explanation: ***Communicates with the 4th ventricle via the aqueduct of Sylvius*** - The **aqueduct of Sylvius** (cerebral aqueduct) is the primary channel connecting the third ventricle to the fourth ventricle, allowing for the flow of **cerebrospinal fluid (CSF)** [3]. - This communication is crucial for the continuous circulation of CSF throughout the ventricular system [1]. *Cavity of the rhombencephalon* - The **rhombencephalon** (hindbrain) develops into the pons, cerebellum, and medulla oblongata, and its cavity forms the **fourth ventricle**, not the third. - The **third ventricle** is derived from the **diencephalon**, a part of the prosencephalon (forebrain). *Communicates exclusively with the lateral ventricles via the foramen of Monro* - The **third ventricle** communicates with the **lateral ventricles** via the **foramina of Monro** (interventricular foramina), but this statement is incorrect because it also communicates with the fourth ventricle [2]. - The term "exclusively" makes this option false, as CSF flows from the lateral ventricles, through the third, and then into the fourth ventricle [1]. *Interthalamic adhesions connect the lateral walls of the 3rd ventricle* - The **interthalamic adhesion** (massa intermedia) is a bridge of gray matter that passes through the **third ventricle**, connecting the medial surfaces of the two thalami. - It does not connect the lateral walls, but rather crosses the cavity itself, and its absence does not typically cause neurological deficits.

Question 1759: Which of the following is NOT a glial cell?

A. Oligodendrocytes
B. Neurons (Correct Answer)
C. Microglia
D. Astrocytes

Explanation: ***Neurons*** - **Neurons** are the primary cells responsible for transmitting electrical and chemical signals throughout the nervous system [3]. - They are distinctly different from glial cells, which primarily provide **support and protection** to neurons [1]. *Oligodendrocytes* - **Oligodendrocytes** are a type of glial cell found in the **central nervous system** (CNS) [1]. - Their main function is to produce **myelin sheaths** that insulate axons, enhancing the speed of nerve impulse transmission [2]. *Microglia* - **Microglia** are the resident **immune cells** of the central nervous system, acting as its primary form of **active immune defense** [1]. - They scavenge for plaques, damaged neurons, and infectious agents, playing a critical role in neuroinflammation and tissue repair [2]. *Astrocytes* - **Astrocytes** are star-shaped glial cells found in the **brain and spinal cord** [1]. - They perform numerous functions, including providing **nutritional support**, maintaining the **blood-brain barrier**, and regulating the **extracellular environment** by controlling ion concentrations.

Question 1760: Cranial nerve VIII passes through which of the following?

A. Foramen ovale
B. Foramen rotundum
C. Internal acoustic meatus (Correct Answer)
D. Stylomastoid foramen

Explanation: ***Internal acoustic meatus*** - The **internal acoustic meatus** is the bony canal that transmits the **vestibulocochlear nerve (CN VIII)**, along with the **facial nerve (CN VII)** and the **labyrinthine artery**, from the posterior cranial fossa to the inner ear [1]. - This passageway is crucial for the functions of hearing and balance mediated by CN VIII [1]. *Foramen ovale* - The **foramen ovale** transmits themandibular nerve **(CN V3)**, which is a branch of the trigeminal nerve, and is involved in mastication and sensory innervation of the lower face. - It also allows passage of the **accessory meningeal artery** and the **emissary veins**. *Foramen rotundum* - The **foramen rotundum** is a passage for the **maxillary nerve (CN V2)**, another branch of the trigeminal nerve, providing sensory innervation to the midface. - It primarily connects the middle cranial fossa with the pterygopalatine fossa. *Stylomastoid foramen* - The **stylomastoid foramen** is the exit point for the **facial nerve (CN VII)** from the skull, after it has passed through the internal acoustic meatus and the facial canal. - It is located between the styloid and mastoid processes of the temporal bone, allowing the facial nerve to emerge and innervate the muscles of facial expression.

Practice by Chapter

Organization of the Nervous System

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Spinal Cord Anatomy

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Brainstem Anatomy

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Cerebellum

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Diencephalon

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Cerebral Cortex

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Basal Ganglia

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Limbic System

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Cranial Nerves

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Autonomic Nervous System

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Neural Pathways and Tracts

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Neurovascular Anatomy

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