Brain and Neuroanatomy Practice Questions

Q: Which structure is marked with a red arrow in the image shown below? (AIIMS May 2018)

Mammillary bodies. ***Mammillary bodies*** - The image shows an **axial view** of the brain, and the red arrow points to paired, rounded structures located on the **inferior surface of the posterior hypothalamus, anterior to the interpeduncular fossa**, consistent with the location of the **mammillary bodies**. - These are part of the **limbic system** and play a crucial role in memory formation through their connections with the hippocampus and thalamus. *Hippocampus* - The hippocampus is located in the **medial temporal lobe**, deeper and more posterior than the structure indicated by the arrow on this axial slice. - It has a characteristic elongated, curved shape, quite distinct from the **paired, rounded structures** shown. *Habenular nuclei* - The **habenular nuclei** are located in the **epithalamus**, superior to the midbrain and posterior to the thalamus, not in the anterior brainstem region indicated. - They are much smaller and are involved in modulating various brain circuits, including those related to pain, stress, and reward. *Amygdala* - The amygdala is an **almond-shaped structure** located deep within the temporal lobe, anterior to the hippocampus. - While close to the region shown, its shape and exact position differ from the **mammillary bodies**, particularly in this axial plane where the mammillary bodies are seen as distinct, round structures near the midline.

Q: The marked extraocular muscle has a cranial nerve nucleus. At what level in the brain is the nucleus located? (AIIMS May 2018)

Superior colliculus. ***Superior colliculus*** - The image shows the **medial rectus muscle** (indicated by the arrow), which controls adduction of the eye. - The medial rectus muscle is innervated by the **oculomotor nerve (CN III)**, and its nucleus is located at the level of the **superior colliculus** in the midbrain. - The superior colliculus is located in the **midbrain** and is involved in visual reflexes and saccadic eye movements. - The **oculomotor nucleus (CN III)** is located ventral to the superior colliculus in the periaqueductal gray at the level of the superior colliculus. - CN III innervates the superior rectus, inferior rectus, medial rectus, and inferior oblique muscles. *Facial colliculus* - The facial colliculus is a bulge on the dorsal surface of the pons, formed by the **facial nerve (CN VII) fibers** wrapping around the **abducens nucleus (CN VI)**. - The **abducens nerve (CN VI)** innervates the lateral rectus muscle, not the medial rectus shown in the image. *Superior olivary nucleus* - The superior olivary nucleus is located in the **pons** and is a critical component of the auditory pathway, involved in sound localization. - It has no role in the innervation of extraocular muscles. *Inferior colliculus* - The inferior colliculus is situated in the **midbrain** and is a major relay center in the auditory pathway. - The **trochlear nucleus (CN IV)** is located at the level of the inferior colliculus and innervates the superior oblique muscle. - However, the inferior colliculus itself does not contain nuclei for extraocular muscle innervation.

Q: Which disease occurs due to involvement of the structure marked in red? (AIIMS May 2018)

Paralysis agitans. ***Paralysis agitans*** - The red circle points to the **midbrain region**, which contains the **substantia nigra**, a key brain structure involved in producing **dopamine**. - **Paralysis agitans**, also known as **Parkinson's disease**, is characterized by the degeneration of dopaminergic neurons in the substantia nigra (located within the marked midbrain region), leading to motor symptoms like tremor, rigidity, and bradykinesia. *Depression* - Depression is a mood disorder associated with imbalances in various **neurotransmitters** (e.g., serotonin, norepinephrine, dopamine) and often involves brain regions such as the prefrontal cortex and limbic system, not primarily the substantia nigra. - While dopamine pathways can be implicated in motivation and reward, the primary pathology of major depression is not direct degeneration of the substantia nigra. *Alzheimer's disease* - Alzheimer's disease is a neurodegenerative disorder primarily characterized by the accumulation of **amyloid plaques** and **neurofibrillary tangles**, leading to neuronal loss and brain atrophy, particularly in the hippocampus and cerebral cortex, not the substantia nigra. - It results in progressive **memory loss** and cognitive decline, distinct from the motor symptoms seen in Parkinson's. *Huntington's chorea* - Huntington's chorea is a hereditary neurodegenerative disease caused by the degeneration of GABAergic neurons in the **striatum** (caudate and putamen). - It is characterized by **involuntary movements** (chorea), cognitive decline, and psychiatric symptoms, which result from basal ganglia dysfunction but not specifically originating from the substantia nigra.

Q: Identify the structure shown. (Recent NEET Pattern 2019)

Cerebellum. ***Cerebellum*** - The arrow in the sagittal MRI view points to the posterior cranial fossa, where the **cerebellum** is located, characterized by its distinctive folia and fissures. - The cerebellum is critical for **motor control**, balance, coordination, and learning motor skills. *Pons* - The **pons** is located anterior to the cerebellum, appearing as a prominent bulge on the brainstem, superior to the medulla. - It primarily acts as a communication bridge between the **cerebrum and cerebellum** and contains nuclei important for sleep, respiration, and bladder control. *Medulla* - The **medulla oblongata** is the lowest part of the brainstem, continuous with the spinal cord, situated inferior to the pons. - It contains vital autonomic centers for **cardiac, respiratory, and vasomotor functions**. *Occipital cortex* - The **occipital cortex** is part of the cerebrum, located at the posterior pole of the brain, superior to the cerebellum, and is responsible for **visual processing**. - It is identifiable by its characteristic gyri and sulci, distinctly different from the highly folded cerebellar folia.

Q: Bilateral occlusion of the anterior cerebral artery (ACA) supplying the area marked in red (paracentral lobule and medial cortex) will lead to all of the following except:

Apraxia (Constructional). ***Apraxia (Constructional)*** - The area marked in red represents the **medial portion of the precentral gyrus (motor cortex)** and **postcentral gyrus (sensory cortex)**, as well as the **paracentral lobule**, which are supplied by the **anterior cerebral artery (ACA)**. - Constructional apraxia is typically associated with **posterior parietal lobe lesions**, particularly in the non-dominant hemisphere, which is supplied by the posterior cerebral artery and middle cerebral artery branches, not the ACA. *Contralateral leg weakness* - The **paracentral lobule** contains the primary motor cortex representation for the **lower limb**. - ACA occlusion affecting this region leads to **contralateral leg weakness (monoplegia or hemiplegia predominantly affecting the leg)**. *Contralateral leg sensory loss* - The **somatosensory cortex** representing the lower limbs is located in the **paracentral lobule** (postcentral gyrus part). - Occlusion of the ACA supplying this region leads to **contralateral sensory deficits in the leg**. *Urinary incontinence* - The **paracentral lobule**, located in the area supplied by the ACA (marked in red), contains centers for **bladder control** and voluntary micturition. - Bilateral damage to this region due to bilateral ACA occlusion can lead to **urinary incontinence** due to disrupted cortical control over bladder function.

Q: What is the name of the marked blood vessel in the Circle of Willis?

Posterior communicating artery. ***Posterior communicating artery*** - The image displays the Circle of Willis, and the vessel marked with 'X' is connecting the **internal carotid artery** (which branches into the middle and anterior cerebral arteries) to the **posterior cerebral artery**. - This connecting artery is the **posterior communicating artery**, an essential component of the Circle of Willis, ensuring collateral blood flow to the brain. *Middle cerebral artery* - The **middle cerebral artery** branches off the internal carotid artery and typically extends laterally into the Sylvian fissure, supplying a large part of the lateral cerebral cortex. - The marked vessel is clearly connecting proximal arteries within the Circle of Willis, not extending into the cerebral cortex peripherally. *Internal carotid artery* - The **internal carotid artery** enters the skull and gives rise to several branches, including the middle cerebral artery and the posterior communicating artery. - While it's part of the supply to the Circle of Willis, the 'X' points specifically to the **communicating segment** connecting the anterior and posterior circulations, not the main trunk of the internal carotid. *Posterior cerebral artery* - The **posterior cerebral artery** is formed by the bifurcation of the basilar artery and supplies the occipital lobe and parts of the temporal lobe. - The marked vessel is connecting to the posterior cerebral artery, but it is not the posterior cerebral artery itself; rather, it is the vessel **communicating** with it from the anterior circulation.

Q: What is the name of the marked blood vessel shown in brain circulation?

Internal carotid artery. ***Internal carotid artery*** - The arrow points to the **internal carotid artery**, a large vessel that ascends from the neck into the skull as part of the **anterior circulation**. - The internal carotid artery enters the cranial cavity and bifurcates into the **anterior cerebral artery** and **middle cerebral artery**, and also gives rise to the posterior communicating artery as part of the **Circle of Willis**. - Its large caliber and characteristic course make it readily identifiable on angiographic imaging such as MRA. *Posterior communicating artery* - The **posterior communicating artery** is a much smaller vessel that connects the internal carotid artery to the posterior cerebral artery, forming part of the Circle of Willis. - It would appear as a small anastomotic branch, not the large prominent trunk indicated by the arrow. *Middle cerebral artery* - The middle cerebral artery is a large artery that branches off the **internal carotid artery** and typically extends laterally and superiorly to supply a large part of the **cerebral hemispheres**. - It would appear more laterally positioned, not in the location indicated by the arrow. *Anterior communicating artery* - The **anterior communicating artery** connects the two **anterior cerebral arteries** at the anterior aspect of the Circle of Willis. - It is a small vessel located at the midline anteriorly, distinct from the large vessel indicated by the arrow.

Q: Identify the image given below.

4th ventricle. ***4th ventricle*** - The arrow points to the **fourth ventricle**, a diamond-shaped, fluid-filled cavity located between the **pons** and **medulla** anteriorly and the **cerebellum** posteriorly on this sagittal MRI image. - This anatomical position — anterior to the cerebellum and posterior to the pons — is characteristic of the **fourth ventricle**. *3rd ventricle* - The **third ventricle** is a narrow midline cavity located between the two thalami, superior to the fourth ventricle. - It communicates with the fourth ventricle via the **cerebral aqueduct (aqueduct of Sylvius)**. *Lateral ventricle* - The **lateral ventricles** are much larger and are located more superiorly within the cerebral hemispheres. - They connect to the third ventricle via the **foramina of Monro**. *Corpus callosum* - The **corpus callosum** is a thick band of white matter connecting the two cerebral hemispheres, located superiorly. - It appears as a solid structure on MRI, not a fluid-filled space.

Q: The glymphatic system is the lymphatic-like structure of which system?

Central Nervous System. ***Central Nervous System*** - The **glymphatic system** is a specialized waste clearance pathway unique to the **central nervous system (CNS)**. - It facilitates the removal of metabolic waste products, including **amyloid-beta**, from the brain, playing a crucial role in CNS health. *Gastro-intestinal* - The gastrointestinal system has its own extensive lymphatic network, including **Peyer's patches** and **mesenteric lymph nodes**, for immune surveillance and lipid absorption. - These structures differ significantly in function and anatomy from the brain's glymphatic system. *Respiratory* - The respiratory system is equipped with **bronchial lymphatics** and **pulmonary lymph nodes** that drain fluid and immune cells from the lungs. - This system is involved in immune responses and fluid balance in the lungs, not directly related to brain waste clearance. *Renal* - The renal system has lymphatic drainage associated with the kidneys, which helps in the return of interstitial fluid and immune cells [1]. - This system is distinct from the glymphatic system and primarily involved in kidney function and fluid balance [1].

Q: Contralateral Homonymous upper quadrantanopia is the type of visual loss seen when the lesion is located at which one of the following anatomical locations?

Temporal lobe. ***Temporal lobe*** - Lesions in the **temporal lobe** disrupt the **Meyer's loop**, which carries contralateral inferior retinal (superior visual field) fibers. - This specific disruption leads to a **contralateral homonymous upper quadrantanopia**, affecting the upper visual field on the side opposite the lesion [1]. *Parietal lobe* - Lesions in the **parietal lobe** typically cause a **contralateral homonymous inferior quadrantanopia**. - This is because the parietal optic radiations carry fibers from the contralateral superior retina (inferior visual field) [1]. *Frontal lobe* - The **frontal lobe** is primarily involved in **eye movements** and **saccades**, not direct processing of visual fields. - Lesions here might cause gaze preferences or motor deficits, but generally not specific quadrantanopias. *Occipital lobe* - Lesions in the **occipital lobe**, especially the visual cortex, result in **contralateral homonymous hemianopia** with **macular sparing** [1]. - A quadrantanopia from an occipital lesion would typically be inferior, and a complete hemianopia is more common.

Question 1

Which structure is marked with a red arrow in the image shown below? (AIIMS May 2018)

Accepted Answer

Mammillary bodies

Answer

Hippocampus

Answer

Habenular

Answer

Amygdala

Question 2

The marked extraocular muscle has a cranial nerve nucleus. At what level in the brain is the nucleus located? (AIIMS May 2018)

Accepted Answer

Superior colliculus

Answer

Facial colliculus

Answer

Inferior colliculus

Answer

Superior olivary nucleus

Question 3

Which disease occurs due to involvement of the structure marked in red? (AIIMS May 2018)

Accepted Answer

Paralysis agitans

Answer

Depression

Answer

Alzheimer's disease

Answer

Huntington's chorea

Question 4

Identify the structure shown. (Recent NEET Pattern 2019)

Accepted Answer

Cerebellum

Answer

Pons

Answer

Medulla

Answer

Occipital cortex

Question 5

Bilateral occlusion of the anterior cerebral artery (ACA) supplying the area marked in red (paracentral lobule and medial cortex) will lead to all of the following except:

Accepted Answer

Apraxia (Constructional)

Answer

Contralateral leg weakness

Answer

Contralateral leg sensory loss

Answer

Urinary incontinence

Question 6

What is the name of the marked blood vessel in the Circle of Willis?

Accepted Answer

Posterior communicating artery

Answer

Middle cerebral artery

Answer

Internal carotid artery

Answer

Posterior cerebral artery

Question 7

What is the name of the marked blood vessel shown in brain circulation?

Accepted Answer

Internal carotid artery

Answer

Middle cerebral artery

Answer

Posterior communicating artery

Answer

Anterior communicating artery

Question 8

Identify the image given below.

Accepted Answer

4th ventricle

Answer

Corpus callosum

Answer

Lateral ventricle

Answer

3rd ventricle

Question 9

The glymphatic system is the lymphatic-like structure of which system?

Accepted Answer

Central Nervous System

Answer

Gastrointestinal

Answer

Respiratory

Answer

Renal

Question 10

Contralateral Homonymous upper quadrantanopia is the type of visual loss seen when the lesion is located at which one of the following anatomical locations?

Accepted Answer

Temporal lobe

Answer

Parietal lobe

Answer

Frontal lobe

Answer

Occipital lobe

Brain and Neuroanatomy — MCQs

Brain and Neuroanatomy — MCQs

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