Neuroanatomy Practice Questions

Q: In postnatal period the greatest growth in the CNS is of?

Dendrite. ***Dendrite*** - Postnatal **brain growth** involves a significant increase in the complexity and number of **dendritic arborizations**. This process is crucial for establishing neural networks and synaptic connections. [1] - The proliferation of dendrites allows for enhanced **synaptic plasticity** and the integration of diverse neural inputs, which is fundamental to learning and development. *Perikaryon* - While the **neuron's cell body (perikaryon)** does grow in size postnatally, the most dynamic and extensive growth in terms of surface area for synaptic contact occurs in the dendritic tree. [1] - The perikaryon primarily houses the nucleus and cellular machinery, which supports overall neuron function, but its growth is less about increasing connectivity compared to dendrites. [2] *Myelin sheath* - **Myelination** is a significant postnatal process that continues into adolescence, increasing the speed of nerve impulses. However, myelination primarily involves the *insulation* of existing axons by glial cells, not a primary growth of the neuron itself. - While essential for mature brain function, it is not the "greatest growth" in terms of neuronal structural elaboration for new connections; rather, it's an enhancement of existing axonal pathways. *Axon* - Axons are largely established during **fetal development** and early postnatal life, forming the principal output pathways of neurons. While axons continue to extend and find targets, their *greatest* period of growth and pathfinding is generally earlier than the most rapid dendritic expansion. - The main postnatal growth related to axons involves their myelination and the formation of new synaptic terminals at their ends, but the dramatic increase in receptive surface area is mainly dendritic.

Q: Most afferent fibers from the lateral geniculate nucleus terminate in which layer of the primary visual cortex:

Layer 4. ***Layer 4*** - The **lateral geniculate nucleus (LGN)** is the primary thalamic relay for visual information. Its afferent fibers directly target and terminate in **Layer 4** (specifically Layer 4C) of the primary visual cortex (V1 or Brodmann area 17). - This layer is characterized by its dense population of **stellate cells**, which are crucial for initial visual processing and relaying information to other cortical layers. *Layer 2 & 3* - These layers (also known as the **supragranular layers**) receive input primarily from layer 4 and are involved in higher-order processing, such as **shape and object recognition**. - They contain **pyramidal neurons** that project to other cortical areas, but they are not the primary termination site for LGN afferents. *Layer 1* - This outermost layer, also known as the **molecular layer**, is relatively cell-sparse and plays a role in **cortical modulation** and integration of synaptic inputs. - It primarily contains axons and dendrites and does not receive direct strong input from the LGN. *Layer 5 & 6* - These layers (also known as the **infragranular layers**) are involved in output from the cortex. Layer 5 contains large **pyramidal cells** that project subcortically (e.g., to the superior colliculus). - Layer 6 projects back to the **thalamus**, including the LGN, thereby modulating its activity, but it is not the primary recipient of LGN afferents.

Q: Anterior spinal artery is a branch of?

Vertebral artery. ***Vertebral artery*** - The **anterior spinal artery** is formed by the union of two small branches, one from each **vertebral artery**, near their junction to form the basilar artery. - It supplies the anterior two-thirds of the **spinal cord**, including the corticospinal tracts and the anterior horn. *Ascending spinal artery* - This is not a commonly recognized major named artery that directly gives rise to the anterior spinal artery. - The arterial supply to the spinal cord is complex, involving main longitudinal arteries and segmental arteries. *Basilar artery* - The **basilar artery** is formed by the union of the two vertebral arteries and supplies the brainstem, cerebellum, and posterior cerebral hemispheres. - While it is a continuation of the vertebral artery system, it does not directly give rise to the anterior spinal artery; rather, the vertebral arteries themselves give off the branches. *Posterior spinal artery* - The **posterior spinal arteries** typically arise directly from the vertebral arteries or from the posterior inferior cerebellar arteries (PICA). - They run along the posterolateral sulci of the spinal cord and supply the posterior one-third of the cord, distinct from the anterior spinal artery's territory.

Q: Which of the following cranial nerves is MOST likely to be damaged in a patient with uncal herniation?

Oculomotor. ***Oculomotor*** - The **oculomotor nerve (CN III)** is particularly vulnerable to compression during uncal herniation because it runs along the tentorial edge, adjacent to the uncus. [1] - Compression typically results in **ipsilateral pupillary dilation** due to involvement of the parasympathetic fibers, followed by ophthalmoplegia affecting eye movements. [1] *Trochlear* - The **trochlear nerve (CN IV)** is less commonly affected in uncal herniation compared to the oculomotor nerve as it courses dorsally around the brainstem. - Damage to the trochlear nerve typically leads to **diplopia** and difficulty with downgaze, especially when looking medially. *Abducens* - The **abducens nerve (CN VI)** has a long intracranial course making it susceptible to conditions that increase intracranial pressure, but not typically direct compression solely from uncal herniation. - Injury to the abducens nerve results in **ipsilateral lateral rectus palsy**, leading to an inability to abduct the eye. *Facial* - The **facial nerve (CN VII)** is located more rostrally and laterally on the brainstem, making it relatively protected from the direct compressive effects of uncal herniation. - Damage to the facial nerve causes **facial weakness or paralysis**, which is not a primary sign of uncal herniation.

Q: Which of the following tracts is responsible for transmitting fine touch and proprioception sensations from the lower body?

Fasciculus gracilis. ***Fasciculus gracilis*** - The **fasciculus gracilis** transmits conscious proprioception, vibratory sense, and **fine touch** from the **lower limbs** and lower trunk [1]. - It is located medially within the dorsal columns and contains axons from sensory neurons entering the spinal cord at **sacral, lumbar, and lower thoracic levels** [1]. *Fasciculus cuneatus* - The **fasciculus cuneatus** carries the same sensory modalities (fine touch, vibration, proprioception) but from the **upper limbs** and upper trunk (above T6) [1]. - It is situated lateral to the fasciculus gracilis in the dorsal columns and terminates in the **nucleus cuneatus** in the medulla [1]. *Posterior spinocerebellar* - The **posterior spinocerebellar tract** conveys **unconscious proprioception** from the lower limbs and trunk to the cerebellum, crucial for muscle coordination. - It does not transmit conscious fine touch and is primarily involved in **motor control** rather than sensation perception. *Rubrospinal tract* - The **rubrospinal tract** is a motor tract originating in the **red nucleus** and primarily involved in controlling the tone of flexor muscles and some voluntary movements. - It plays no role in transmitting sensory information like fine touch or proprioception.

Q: Lacrimation is affected when facial nerve injury is at:

Geniculate ganglion. ***Geniculate ganglion*** - The **greater petrosal nerve** branches from the facial nerve at the **geniculate ganglion** and carries preganglionic parasympathetic fibers to the **pterygopalatine ganglion**, which supplies the **lacrimal gland**. - An injury at or just distal to the **geniculate ganglion** (affecting the greater petrosal nerve) will specifically impair **lacrimation** while potentially sparing more distal functions. - This is the **most proximal intratemporal location** where isolated lacrimal dysfunction can occur, making it the classic answer for lacrimation deficits in facial nerve injuries. *Cerebellopontine angle* - A lesion at the **cerebellopontine angle (CPA)** affects the facial nerve **before entry into the internal acoustic meatus**, which is **proximal to the geniculate ganglion**. - While CPA lesions would technically affect lacrimation (along with ALL facial nerve functions), they are **too proximal and non-specific** for this question. - CPA lesions cause global facial nerve dysfunction (motor, taste, lacrimation, hyperacusis), not isolated lacrimal problems. - The question asks for the specific anatomical landmark associated with lacrimation deficits = **geniculate ganglion/greater petrosal nerve**. *Mastoid segment* - Injury to the facial nerve in the **mastoid segment** is **distal** to the origin of the greater petrosal nerve and the nerve to stapedius. - While it affects the **chorda tympani** (taste from anterior two-thirds of tongue) and motor function distal to it, **lacrimation is preserved**. *At Stylomastoid foramen* - The **stylomastoid foramen** is the exit point of the facial nerve from the skull. - Injury here causes **facial paralysis** (motor function to muscles of facial expression) but **spares lacrimation, taste, and stapedius function** as these nerves have already branched off proximally.

Q: All of the following contains Bipolar neurons except

Dorsal root ganglion. ***Dorsal root ganglion*** - Dorsal root ganglia predominantly contain **pseudounipolar neurons**, which have a single process that branches into peripheral and central axons [3]. - These neurons are responsible for transmitting **sensory information** from the periphery to the central nervous system. - **This is the correct answer** as it does NOT contain bipolar neurons. *Retina* - The retina contains **bipolar cells**, which are interneurons that transmit signals from photoreceptors to ganglion cells [2]. - These bipolar neurons are crucial for **visual signal processing** [2]. *Olfactory bulb* - The olfactory bulb contains several types of neurons including **periglomerular cells and some interneurons that are bipolar in nature**. - It receives input from olfactory receptor neurons and processes **olfactory information**. *Olfactory epithelium* - The olfactory epithelium contains **olfactory receptor neurons**, which are true bipolar neurons [1]. - These specialized neurons have one dendrite extending to the surface and one axon projecting to the olfactory bulb, making them classic examples of bipolar neurons [1]. - These neurons are responsible for detecting **odors** and transmitting signals to the olfactory bulb [1].

Q: The spinal nerve pairs are :

31. ***31*** - There are 31 pairs of **spinal nerves** that emerge from the spinal cord. - These pairs are organized into cervical (8), thoracic (12), lumbar (5), sacral (5), and coccygeal (1) segments, each serving specific regions of the body. *30* - This number is incorrect; the total number of **spinal nerve pairs** is higher than 30. - Focusing on individual segments, like the 8 cervical nerves, shows that the total adds up differently. *33* - While there are 33 vertebrae during development (some fuse in the sacrum and coccygeal), the number of **spinal nerve pairs** is 31, not 33. - The number of spinal nerves does not directly correlate with the number of individual vertebral bones in adulthood. *28* - This number is significantly lower than the actual count of **spinal nerve pairs**. - The human spinal cord gives rise to a greater number of nerves to innervate the entire body.

Q: A 32-year-old woman is admitted to the hospital after losing consciousness and collapsing in the middle of the street. A neurologic examination reveals absence of the accommodation reflex of her right eye. Which of the following is most likely involved in the pathology in this patient?

Edinger-Westphal nucleus. ***Edinger-Westphal nucleus*** - The **Edinger-Westphal nucleus** contains **preganglionic parasympathetic neurons** that project via the oculomotor nerve to the ciliary ganglion, controlling the **pupillary constrictor (sphincter pupillae) and ciliary muscles** [1]. - Its involvement would directly impair the **accommodation reflex** and pupillary constriction, which aligns with the absence of the accommodation reflex in the right eye [1]. *Nervus intermedius* - The **nervus intermedius** is a part of the facial nerve (cranial nerve VII) that carries **sensory and parasympathetic fibers** for taste from the anterior tongue and innervation of the submandibular and sublingual glands. - Its pathology would primarily affect **taste sensation** or salivary gland function, not the accommodation reflex. *Superior salivatory nucleus* - The **superior salivatory nucleus** is a brainstem nucleus that provides **preganglionic parasympathetic innervation** to the lacrimal glands and submandibular/sublingual salivary glands via the facial nerve. - Dysfunction here would affect **tear production** or salivation, not the intrinsic eye muscles responsible for accommodation. *Superior cervical ganglion* - The **superior cervical ganglion** is a part of the **sympathetic nervous system**, providing postganglionic sympathetic innervation to the head and neck, including the **dilator pupillae muscle** [2]. - Damage to this ganglion would cause a **Horner's syndrome** (miosis, ptosis, anhydrosis), which affects pupillary dilation, not accommodation [2].

Q: Cell bodies of the neurons which carry taste sensation from the anterior 2/3rd of the tongue are located in:

Geniculate ganglion. ***Geniculate ganglion*** - The **geniculate ganglion** is primarily associated with the **facial nerve (CN VII)**, which carries taste sensations from the **anterior two-thirds of the tongue** via the chorda tympani [1]. - The cell bodies of the **pseudounipolar neurons** responsible for this taste sensation are located within this ganglion [1]. *Superior cervical ganglion* - This ganglion is part of the **sympathetic nervous system** and is involved in innervating structures in the head and neck, such as the pupillary dilator muscles and salivary glands. - It does not contain cell bodies for taste sensation. *Otic ganglion* - The **otic ganglion** is a parasympathetic ganglion associated with the **glossopharyngeal nerve (CN IX)** and is involved in salivation from the parotid gland. - It does not contain taste neuron cell bodies for the tongue. *Trigeminal ganglion* - The **trigeminal ganglion** (Gasserian ganglion) contains the cell bodies of sensory neurons for general sensation (touch, pain, temperature) from the face, including the tongue and oral cavity. - It does not carry taste sensation.

Question 1

In postnatal period the greatest growth in the CNS is of?

Accepted Answer

Dendrite

Answer

Perikaryon

Answer

Myelin sheath

Answer

Axon

Question 2

Most afferent fibers from the lateral geniculate nucleus terminate in which layer of the primary visual cortex:

Accepted Answer

Layer 4

Answer

Layer 2 & 3

Answer

Layer 1

Answer

Layer 5 & 6

Question 3

Anterior spinal artery is a branch of?

Accepted Answer

Vertebral artery

Answer

Ascending spinal artery

Answer

Basilar artery

Answer

Posterior spinal artery

Question 4

Which of the following cranial nerves is MOST likely to be damaged in a patient with uncal herniation?

Accepted Answer

Oculomotor

Answer

Trochlear

Answer

Abducens

Answer

Facial

Question 5

Which of the following tracts is responsible for transmitting fine touch and proprioception sensations from the lower body?

Accepted Answer

Fasciculus gracilis

Answer

Fasciculus cuneatus

Answer

Posterior spinocerebellar

Answer

Rubrospinal tract

Answer

Lateral spinothalamic tract

Question 6

Lacrimation is affected when facial nerve injury is at:

Accepted Answer

Geniculate ganglion

Answer

Mastoid segment

Answer

Cerebellopontine angle

Answer

At Stylomastoid foramen

Question 7

All of the following contains Bipolar neurons except

Accepted Answer

Dorsal root ganglion

Answer

Retina

Answer

Olfactory bulb

Answer

Olfactory epithelium

Question 8

The spinal nerve pairs are :

Accepted Answer

31

Answer

30

Answer

33

Answer

28

Question 9

A 32-year-old woman is admitted to the hospital after losing consciousness and collapsing in the middle of the street. A neurologic examination reveals absence of the accommodation reflex of her right eye. Which of the following is most likely involved in the pathology in this patient?

Accepted Answer

Edinger-Westphal nucleus

Answer

Nervus intermedius

Answer

Superior salivatory nucleus

Answer

Superior cervical ganglion

Question 10

Cell bodies of the neurons which carry taste sensation from the anterior 2/3rd of the tongue are located in:

Accepted Answer

Geniculate ganglion

Answer

Superior cervical ganglion

Answer

Otic ganglion

Answer

Trigeminal ganglion

Neuroanatomy — MCQs

Neuroanatomy — MCQs

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