Past Questions - Structural/Functional Neuroanatomy

Question 1

Describe the lateral nuclei of the thalamus

Answer 1

Lateral Nuclei: Formed of 2 Lateral + 4 Ventral + 2 Metathalamic + 1 Pulvinar or Posterior.

• Lateral Dorsal: Prefrontal and Limbic afferents, reproject to the cortex.
  • Attention, working memory, execution.
  Receives input from the Limbic system and Prefrontal cortex by thalamocortical projection.
• Lateral Posterior: Primary somatosensory cortex (S1) and Superior/Visual Colliculus afferents. Connected to
  Optic/Somatosensory radiations.
  • Somatosensory and visual-spatial processing.
  Receives inputs from Superior/Visual colliculus, S1. Connections to the Optic radiation and Somatosensory radiations.

Question 2

Macroscopic anatomy of midbrain (mesencephalon), describing also a 1⁄3 transverse section of the structure

Answer 2

The midbrain (mesencephalon) is the uppermost portion of the brainstem. It is a small yet vital structure involved in motor control, sensory processing, and reflexes. Its macroscopic anatomy includes:

1. Tectum (Dorsal Portion):
   • Contains the superior colliculi (responsible for visual reflexes) and the inferior colliculi (responsible for auditory reflexes).
2. Cerebral Peduncles (Ventral Portion):
   • Large bundles of nerve fibers that connect the forebrain to the hindbrain, carrying motor and sensory information.
3. Substantia Nigra:
   • A pigmented area involved in movement regulation, part of the basal ganglia system.
4. Red Nucleus:
   • A structure involved in motor coordination, particularly controlling limb movements.
5. Cerebral Aqueduct:
   • A narrow channel connecting the third and fourth ventricles, allowing cerebrospinal fluid (CSF) to flow through the brain.

The midbrain is a compact structure located between the diencephalon and pons.

Midbrain Transverse section (Levels: Sup. + Inf. Colliculi)
Sup.colliculi = Brachia of SC and CN3, RED and Edinger-Westphal Nuclei
Inf.colliculi = Brachia of IC and CN4, Aqueduct of Sylvius

Question 3

Describe the structures characterizing the dorsal surface of the medulla oblongata.

Answer 3

The dorsal surface of the medulla oblongata is characterized by:

1. Gracile and Cuneate Tubercle – Elevations over the gracile and cuneate nuclei, which process sensory input.
2. Posterior Median Sulcus – A midline groove dividing the medulla dorsally.
3. Fasciculus Gracilis and Cuneatus – Longitudinal ridges carrying sensory fibers for fine touch and proprioception.
4. Obex – Transition point where the fourth ventricle narrows into the central canal.
5. Inferior Cerebellar Peduncles – Fiber bundles linking the medulla to the cerebellum.
6. Fourth Ventricle – The dorsal medulla forms part of its floor, holding cerebrospinal fluid.

Question 4

Describe the morphology and topography of the substantia nigra. Also describe its function and its dopaminergic role in the basal ganglia circuitry.

Answer 4

Morphology and Topography:
• The substantia nigra is a pigmented, crescent-shaped structure located in the midbrain, beneath the cerebral peduncles.

It consists of two parts:
1. Pars compacta (SNc): Contains densely packed dopaminergic neurons with melanin, giving it a dark appearance.
2. Pars reticulata (SNr): Composed of GABAergic neurons and functions as an output nucleus of the basal ganglia.

Function and Dopaminergic Role:
• The substantia nigra is critical for motor control, reward, and learning.
• The dopaminergic neurons of the pars compacta project to the striatum (caudate nucleus and putamen) in the basal ganglia circuitry.
• Dopamine modulates motor activity by regulating the direct pathway (facilitates movement) and indirect pathway (inhibits unwanted movement).
• Degeneration of these dopaminergic neurons leads to movement disorders like Parkinson’s disease.

Question 5

Describe cerebellar cell layers, fibers and glomerulus

Answer 5

Grey matter consists of 3 layers:

1) Molecular: Outer layer, granule cell axons and parallel fibers, purkinje dendrites. Regulated by basket and stellate cells
2) Purkinje: Middle output layer, purkinje cell bodies regulated by climbing fibers projected from inf. Olivary nucleus
3) Granular: Inner layer, input from cortex, spine and brainstem carried by mossy fibers and regulated by golgi cells.

Cerebellar Glomerulus:
• A synaptic complex in the granule layer, where mossy fibers, granule cell dendrites, and Golgi cell axons interact.
• It is a site of integration for sensory and motor input.

Question 6

Describe cerebral cortex cell layers, zonal differences, Brodmann’s areas, functional areas, operculum

Answer 6

Cerebral cortex is composed of 6 layers:

1) Molecular: few neurons, horizontal connections
2) Ext. Granular: small granule cells for sensory information
3) Ext. Pyramidal: medium size pyramidal cells for L/R hemisphere coordination
4) Int. Granular: large granule cells for sensory thalamo-cortico projections
5) Int. Pyramidal: large pyramidal cells for motor pathways
6) Polymorphic: feedback projection between thalamus and cortex

Brodmann’s areas are regions of the cerebral cortex defined by their distinct cytoarchitecture. They correspond to specific functions, including motor control.

Primary Somatosensory: 3/1/2
Associative Somatosensory: 5/7
Primary Motor: 4 Pre-motor: 6 (SMA) / 8 (FEF) Broca’s: 44/45
Pre-frontal: 9/10/11
Primary Visual: 17
Associative Visual: 18/19
Primary Auditory: 41 (Herschl’s Gyri)
Associative Auditory: 42/22 (Wernicke)

Operculum is a part of cerebral cortex covering the insula, involved in frontal, parietal and temporal lobes. Motor control, sensory processing and auditory processing depending on the involved lobe.

Question 7

Describe the structures characterizing the ventral surface of the medulla oblongata.

Answer 7

The ventral surface of the medulla oblongata is characterized by:

1. Pyramids – Longitudinal ridges formed by descending corticospinal tracts, involved in voluntary motor control.
2. Pyramidal Decussation – A crossover of motor fibers at the lower medulla, allowing contralateral motor control.
3. Olives – Oval-shaped elevations lateral to the pyramids, overlying the inferior olivary nuclei, which are involved in motor learning and coordination.
4. Anterior Median Fissure – A groove along the midline that separates the two pyramids.

These structures highlight the medulla’s role in motor and sensory pathways.

Question 8

Describe rhomboid fossa

Answer 8

The rhomboid fossa is the floor of the fourth ventricle, located between the pons and the medulla oblongata. It has a diamond-shaped structure with the following features:
• Median Sulcus: Divides the fossa into right and left halves.
• Medial Eminence: Raised areas on either side of the median sulcus, containing the facial colliculus.
• Facial Colliculus: Elevations formed by fibers of the facial nerve looping around the abducens nucleus.
• Striae Medullares: Horizontal fibers marking the boundary between the pons and medulla regions.
• Sulcus Limitans: Separates the medial motor nuclei from the lateral sensory nuclei.

The rhomboid fossa houses nuclei related to cranial nerves (e.g., V-XII) and plays a role in autonomic and sensory functions.

Question 9

Somatic somitic nuclei of the brainstem topography and function vs Somatic branchial motor nuclei, functional and topographical description

Answer 9

Somatic somitic nuclei of the brainstem are motor nuclei derived from somites and are responsible for controlling skeletal muscles. They are located in the medial motor column of the brainstem

CN-3-4-6-12 = Eye movement, tongue
movement

Somatic branchial motor nuclei are located in the brainstem and control muscles derived from the branchial (pharyngeal) arches. They are involved in motor functions related to facial expression, mastication, swallowing, and phonation.

CN-5-7-9-10-11 = face muscles,
mastication, swallowing, head and neck movement

Question 10

Basal ganglia, macroscopic description, with care to make some references to the topography of the white matter

Answer 10

The basal ganglia are a group of subcortical nuclei involved in motor control, learning, and emotional regulation. Macroscopically, they include:

1. Caudate Nucleus:
   • C-shaped structure located along the lateral wall of the lateral ventricle.
   • Lies medial to the internal capsule.
2. Putamen:
   • Located lateral to the caudate and separated from it by the anterior limb of the internal capsule.
   • Forms the striatum with the caudate.
3. Globus Pallidus:
   • Divided into internal (medial) and external (lateral) segments.
   • Lies medial to the putamen and lateral to the internal capsule.
4. Subthalamic Nucleus:
   • Found below the thalamus and above the substantia nigra in the diencephalon.
5. Substantia Nigra:
   • Located in the midbrain, containing dopaminergic neurons that influence basal ganglia activity.

White Matter Topography:
• The internal capsule, a major white matter structure, separates the caudate nucleus and thalamus medially from the putamen and globus pallidus laterally.
• The external capsule and extreme capsule are lateral white matter tracts flanking the putamen and claustrum.

These structures interact via complex circuits to regulate voluntary movement and inhibit unwanted motor activity.

Question 11

Describe visceral motor nuclei of brainstem

Answer 11

Visceral motor nuclei of the brainstem are autonomic (parasympathetic) nuclei that regulate involuntary functions, such as glandular secretion, heart rate, and smooth muscle activity.

Key Nuclei and Functions:
1. Edinger-Westphal Nucleus (Midbrain):
• Associated with the oculomotor nerve (CN III).
• Controls pupillary constriction and lens accommodation via the ciliary ganglion.

2. Superior Salivatory Nucleus (Pons):
   • Associated with the facial nerve (CN VII).
   • Stimulates lacrimal, nasal, submandibular, and sublingual glands.
3. Inferior Salivatory Nucleus (Medulla):
   • Associated with the glossopharyngeal nerve (CN IX).
   • Stimulates the parotid gland via the otic ganglion.
4. Dorsal Motor Nucleus of Vagus (Medulla):
   • Associated with the vagus nerve (CN X).
   • Regulates parasympathetic control of thoracic and abdominal viscera (e.g., heart, lungs, and gastrointestinal tract).

These nuclei are located in the brainstem’s lateral regions and are integral to parasympathetic autonomic control.

Question 12

Describe the somatotopy and morphology of the internal capsule

Answer 12

The internal capsule is a white matter structure in the brain that contains ascending and descending fibers connecting the cerebral cortex with subcortical structures. It has a characteristic “V-shape” in horizontal sections and is divided into distinct parts:

Morphology:
1. Anterior Limb:
• Lies between the caudate nucleus (medially) and the putamen (laterally).
• Contains frontopontine fibers and fibers connecting the thalamus with the frontal lobe.

2. Genu:
   • The bend of the “V.”
   • Contains corticobulbar fibers, which control cranial nerve motor functions.
3. Posterior Limb:
   • Lies between the thalamus (medially) and the lentiform nucleus (laterally).
   • Contains corticospinal fibers (motor pathways), sensory fibers, and visual/auditory fibers.
4. Retrolenticular Part:
   • Located posterior to the lentiform nucleus.
   • Carries fibers of the optic radiation to the occipital lobe.
5. Sublenticular Part:
   • Located beneath the lentiform nucleus.
   • Contains auditory fibers running to the temporal lobe.

Somatotopy (Posterior Limb):
• The fibers in the posterior limb are somatotopically organized:
• Face fibers (corticobulbar) are anterior.
• Upper limb fibers are located medially.
• Trunk fibers are intermediate.
• Lower limb fibers are posterior.

The internal capsule’s organization ensures precise communication between the cortex and subcortical structures, critical for motor and sensory function.

Question 13

Describe the intracranial meninges and differences between their features at cranial and spinal levels

Answer 13

The intracranial meninges are three protective layers surrounding the brain and spinal cord, providing structural support, circulation of cerebrospinal fluid (CSF), and protection.

Layers of Meninges:
1. Dura Mater:
• Outermost, tough fibrous layer.
• Cranially, it has two layers: periosteal (adheres to the skull) and meningeal (inner layer). These layers form venous sinuses.
• Spinal dura has only the meningeal layer, separated from the vertebrae by the epidural space.
2. Arachnoid Mater:
• Middle, thin avascular membrane.
• Connected to the pia mater by trabeculae and forms the subarachnoid space (contains CSF).
• Similar in cranial and spinal regions but is tightly adhered to the dura at both levels.
3. Pia Mater:
• Innermost delicate layer, adheres closely to the brain and spinal cord.
• Cranially, follows the brain’s contours, including sulci.
• Spinal pia is thicker and forms denticulate ligaments for stabilization.

Key Differences (Cranial vs. Spinal Meninges):

1. Dura Mater:
   • Cranial: Has two layers (periosteal and meningeal), with venous sinuses formed between them.
   • Spinal: Only the meningeal layer is present, and it is separated from the vertebrae by the epidural space.
   
   2. Epidural Space:
      • Cranial: A potential space between the periosteal dura and the skull (normally closed).
      • Spinal: A real space between the spinal dura and the vertebrae, containing fat and venous plexuses.
   3. Arachnoid Mater:
      • Cranial: Closely adheres to the dura and forms subarachnoid cisterns, such as the cisterna magna.
      • Spinal: Similar in structure but does not form cisterns like in the cranial region.
   4. Pia Mater:
      • Cranial: Thin and follows the brain’s sulci and gyri.
      • Spinal: Thicker and forms denticulate ligaments that anchor the spinal cord to the dura for stabilization.

The cranial meninges are specialized for the rigid skull environment, while the spinal meninges accommodate mobility and flexibility.

Question 14

Describe the morphology, topography and the functionality of the striatum

Answer 14

Morphology

The striatum is a subcortical structure composed mainly of gray matter. It consists of two major parts:
• Caudate nucleus – A C-shaped structure following the lateral ventricle.
• Putamen – A large, rounded structure lateral to the caudate.
• Nucleus accumbens – Located at the junction of the caudate and putamen, involved in reward processing.

The striatum appears striated due to white matter fibers of the internal capsule passing through it.

Topography
• Located deep within the telencephalon.
• Lies lateral to the thalamus and medial to the external capsule.
• Functionally, it is part of the basal ganglia and communicates with the cerebral cortex, thalamus, and brainstem.

Functionality
• Motor Control: Regulates voluntary movement by modulating signals from the cortex to the motor pathways.
• Cognitive Functions: Involved in learning, habit formation, and decision-making.
• Reward and Motivation: Plays a key role in the dopamine-mediated reward system, influencing behaviors and emotions.

Dysfunction of the striatum is associated with movement disorders like Parkinson’s and Huntington’s disease, as well as psychiatric conditions such as OCD and addiction.

Question 15

Describe the macroscopic and microscopic anatomy of hippocampus

Answer 15

Macroscopic Anatomy
• A curved, seahorse-shaped structure in the medial temporal lobe.
• Part of the limbic system, crucial for memory and learning.
• Divided into head, body, and tail, extending from the amygdala to the fornix.

Microscopic Anatomy
• Composed of gray matter with three main regions:
• Cornu Ammonis (CA1–CA4) – Pyramidal neurons for memory processing.
• Dentate Gyrus – Granule cells involved in neurogenesis.
• Subiculum – Connects to cortical areas.
• Functions via a trisynaptic circuit essential for memory consolidation.

Function
• Key role in memory formation, learning, and spatial navigation.
• Damage leads to memory loss (e.g., in Alzheimer’s disease).

Question 16

Describe the somatic somitic motor column

Answer 16

The somatic motor column is a group of motor neurons located in the ventral horn of the spinal cord and the brainstem motor nuclei. It extends along the entire length of the spinal cord and innervates muscles derived from somites.

• Controls voluntary movements by innervating skeletal muscles.
• Includes alpha and gamma motor neurons, which regulate muscle contraction and tone.
• Innervates muscles of the limbs, trunk, and tongue (e.g., hypoglossal nerve in the brainstem).
• Lesions in the somatic motor column can cause muscle weakness, paralysis, or atrophy, as seen in spinal cord injuries or motor neuron diseases (e.g., ALS).

Question 17

Describe the medullary part of the rhomboidal fossa with particular attention to the cranial nuclei in the area.

Answer 17

The rhomboid fossa forms the floor of the fourth ventricle. Its medullary part (lower portion) corresponds to the open medulla and contains important cranial nerve nuclei.

• Cranial Nuclei in the Medullary Part
  
  1. Hypoglossal Nucleus (XII) – Located near the midline in the hypoglossal trigone, controls tongue muscles.
  2. Dorsal Motor Nucleus of Vagus (X) – Found lateral to the hypoglossal nucleus, responsible for parasympathetic innervation to thoracic and abdominal organs.
  3. Nucleus Ambiguus (IX, X, XI) – A motor nucleus controlling muscles of the pharynx, larynx, and soft palate.
  4. Solitary Nucleus (VII, IX, X) – Processes taste (VII, IX) and visceral sensory information (IX, X).
  5. Vestibular Nuclei (VIII) – Located laterally, involved in balance and equilibrium.

• Lesions in this region can lead to dysphagia, tongue paralysis, autonomic dysfunction, and balance issues (e.g., lateral medullary syndrome).

Question 18

Explain macroscopically, anatomically and functionally the globus pallidus

Answer 18

Macroscopic Anatomy
• The globus pallidus is a lens-shaped structure within the basal ganglia, located medial to the putamen.
• It is divided into two parts:
1. Globus Pallidus Internus (GPi) – Major output nucleus of the basal ganglia.
2. Globus Pallidus Externus (GPe) – Modulates activity within the basal ganglia circuitry.

Anatomical Connections
• Receives input from the striatum (caudate + putamen).
• GPi sends inhibitory output to the thalamus, which influences motor cortex activity.
• GPe interacts with the subthalamic nucleus to regulate movement control.

Function
• Plays a crucial role in motor control, regulating voluntary movements by inhibiting unwanted movements.
• Involved in the indirect and direct pathways of the basal ganglia, modulating motor activity.
• Dysfunction is linked to movement disorders such as Parkinson’s disease and Huntington’s disease.

Question 19

Describe the inferior triangle of the rhomboid fossa and the underlying nuclei of the cranial nerves

Answer 19

The inferior triangle is the lower part of the rhomboid fossa, forming part of the floor of the fourth ventricle in the medulla oblongata. It is bordered by the hypoglossal and vagal trigones and contains vital cranial nerve nuclei.

• Underlying Cranial Nuclei
  
  1. Hypoglossal Nucleus (XII) – Located in the hypoglossal trigone, controls tongue movements.
  2. Dorsal Motor Nucleus of Vagus (X) – Situated in the vagal trigone, provides parasympathetic innervation to thoracic and abdominal organs.
  3. Solitary Nucleus (VII, IX, X) – Processes taste (VII, IX) and visceral sensory information (IX, X).

• Lesions in this area can cause tongue paralysis (hypoglossal dysfunction), autonomic disturbances (vagus involvement), and loss of taste or visceral sensation.

Question 20

Describe the role of the substantia gelatinosa of Rolando and the ‘gate-control’ hypothesis

Answer 20

The substantia gelatinosa of Rolando is located in the dorsal horn of the spinal cord. It is composed of interneurons that modulate pain and temperature signals from primary sensory neurons before transmitting them to the brain via the spinothalamic tract. It plays a crucial role in pain inhibition through interactions with descending pathways.

The gate-control hypothesis suggests that pain perception is modulated at the spinal coed level. Painless stimuli such as touch and pressure activate inhibitory interneurons in substantia gelatinosa, which can close the gate to pain signals travelling to the brain. It also explains why rubbing a painful area can reduce pain sensation by stimulating Aβ fibers which inhibit C fiber pain transmission.

Question 21

Describe the the structures in the ventral surface of the brainstem

Answer 21

1. Midbrain:
   • Cerebral peduncles – Large bundles of motor fibers connecting the cerebrum to the brainstem.
   • Interpeduncular fossa – A depression between the cerebral peduncles, housing the interpeduncular nucleus.
2. Pons:
   • Basilar pons – A broad area of transverse fibers forming the bridge between the two cerebellar hemispheres.
   • Corticospinal tracts – Major motor pathways running through the pons to the spinal cord.
3. Medulla Oblongata:
   • Pyramids – Prominent structures on the anterior surface formed by corticospinal fibers; the decussation of the pyramids occurs here, where motor fibers cross to the opposite side.
   • Olives – Paired oval structures lateral to the pyramids, involved in motor coordination and sensory processing.

The ventral brainstem is crucial for motor pathways, including voluntary movements via corticospinal tract and coordination via cerebellar connections. It also contains centers for vital functions like heart rate, respiration, and reflexes.

Question 22

Describe a cross section of the cervical portion of the spinal cord, describing both white and gray matter organization

Answer 22

Gray Matter
• The gray matter is centrally located in the shape of an H or butterfly.
• Divided into anterior (ventral) horns (motor neurons), posterior (dorsal) horns (sensory neurons), and the lateral horns (present only in the cervical and thoracic regions, involved in autonomic functions).
• The gray commissure connects the left and right sides of the gray matter.

White Matter
• Surrounding the gray matter, the white matter is divided into three funiculi:
• Dorsal (posterior) columns: Carry sensory information (touch, proprioception).
• Lateral columns: Contain both ascending sensory tracts and descending motor tracts.
• Ventral (anterior) columns: Primarily contain motor tracts.

Function
• Gray matter processes sensory and motor signals, while white matter carries these signals up and down the spinal cord.

Question 23

Describe the macroanatomy of thalamus and functionality (nuclei and internal organization)

Answer 23

Thalamus: Macroanatomy & Functionality

Macroanatomy
• The thalamus is a paired, egg-shaped structure located deep in the diencephalon, forming the lateral walls of the third ventricle.
• It is divided into two halves by the interthalamic adhesion (massa intermedia).

The thalamus is organized into multiple nuclei, which are grouped by function:
1. Sensory nuclei relay sensory information from the body to the somatosensory cortex.
2. Motor nuclei relay motor information from the basal ganglia and cerebellum to the motor cortex.
3. Association nuclei integrate sensory and motor information to support cognitive functions like attention.
4. Limbic nuclei contribute to emotional and memory functions.

The thalamus acts as a relay station for sensory and motor signals, directing information to specific regions of the cerebral cortex. It also plays a key role in consciousness, sleep, and awareness.

Question 24

Frontal lobe dorsal lateral side sulci and gyri + functional areas

Answer 24

Sulci and Gyri
• Superior, middle, and inferior frontal gyri: Involved in cognitive functions and motor control.
• Precentral sulcus: Separates the motor cortex from other regions.

Functional Areas:
1. Primary Motor Cortex: Controls voluntary movement (precentral gyrus).
2. Premotor Cortex: Motor planning (middle frontal gyrus).
3. Prefrontal Cortex: Executive functions like decision-making.
4. Broca’s Area: Speech production (inferior frontal gyrus, left hemisphere).

They work together to control motor skills, cognition, and speech production.