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NEUROSCIENCES – HISTOLOGY
Compiled Topical Questions of Neuroscience – Histology
This organelle is responsible for protein synthesis and is found only in the soma and dendrites, not in the axon .
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Tags:
2020
About the axons of the peripheral nerve, which of the following is incorrect?
Axons of peripheral nerves do NOT contain Nissl substance.
Nissl substance (Nissl bodies) refers to the rough endoplasmic reticulum (RER) and ribosomes , which are abundant in the cell body (perikaryon) and dendrites but are absent in the axon .
This is because protein synthesis does not occur in axons , as ribosomes and RER are needed for protein production, which is instead carried out in the cell body .
Why the Other Options Are Correct?
It may arise from axon hillock ✅
True , because axons originate from the axon hillock , which is a specialized region of the neuron’s cell body that lacks Nissl substance and is involved in action potential initiation.
It transmits action potential ✅
True , because the primary function of an axon is to transmit action potentials away from the neuron’s cell body to the next neuron or effector organ.
It may arise from the perikaryon (Soma) ✅
True , because in some neurons (e.g., unipolar neurons in the dorsal root ganglion), the axon can directly arise from the cell body (soma) .
It may arise from a dendrite ✅
True , but rare. In some sensory neurons , particularly in the olfactory system , the axon may originate from a modified dendrite .
This structure, located in the dorsal horn , plays a key role in regulating pain signals before they are relayed to the brain.
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“What part of a neuron is covered with myelin and responsible for transmitting electrical impulses over long distances?”
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Tags:
2020
What does the white matter of the spinal cord consist of?
The white matter of the spinal cord consists primarily of myelinated axons that form ascending (sensory) and descending (motor) tracts . The myelin sheath , produced by oligodendrocytes , gives the white matter its characteristic pale appearance and is crucial for fast signal transmission via saltatory conduction .
Why the Other Options Are Wrong:
Perikarya (Neuron cell bodies) – These are mainly found in the gray matter , not white matter. The gray matter contains neuron somas , such as those in the anterior horn (motor neurons) and posterior horn (sensory neurons) .
Dendrites – While dendrites are found in gray matter where synapses occur , they are not a major component of white matter, which consists mostly of axons .
Neuroglia – While glial cells (astrocytes, oligodendrocytes, and microglia) are present in white matter, they are not the primary component . The main function of white matter is axonal conduction , not glial support.
Blood vessels – Although white matter contains blood vessels to supply oxygen and nutrients , they are not the defining structural component of white matter.
The molecular layer of the cerebellar cortex primarily contains interneurons (stellate and basket cells) , parallel fibers , and neuroglia . The cell bodies of Purkinje cells are located in a separate layer (Purkinje cell layer), but their dendrites extend into the molecular layer.
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Think about the structural organization of the cerebral and cerebellar cortices. Which part of the brain has a more complex layered structure, and which has a simpler one?
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“Which layer of the dura mater remains tightly attached to the skull, preventing direct penetration by veins?”
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Look for large, flask-shaped cells arranged in a single layer, responsible for the output of the cerebellar cortex.
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“Which nucleus controls the diaphragm and is associated with motor function rather than sensory processing?”
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Focus on the layer where dendrites of Purkinje cells branch extensively and interact with parallel fibers and interneurons.
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“Which histological change is an early marker of neuronal death in stroke or ischemia?”
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Tags:
2020
Which one of the following statements refers to red neurons?
Red neurons are a hallmark of acute neuronal injury , typically due to hypoxic-ischemic damage (e.g., stroke, global ischemia). They appear within 12–24 hours after injury and are characterized by:
Shrinkage of the cell body
Loss of Nissl substance (which normally contains rough endoplasmic reticulum for protein synthesis)
Pyknosis of the nucleus (nuclear condensation and darkening)
Intensely eosinophilic (bright red) cytoplasm , giving them their name
Why the Other Options Are Wrong:
Abnormal vacuolization of neuron – This is more characteristic of spongiform encephalopathies (e.g., Creutzfeldt-Jakob disease ), not red neurons.
Structural loss along with functional loss of the neuron – While red neurons indicate functional loss , this option is too vague. The key histological features are cytoplasmic eosinophilia, nuclear pyknosis, and Nissl substance loss .
Reactive astrogliosis – This occurs as part of the chronic response to injury, where astrocytes proliferate and form a glial scar . It does not describe the acute phase of red neurons.
Neurons having bright pink cytoplasm with large nucleus and numerous stout ramifying processes – This describes reactive astrocytes (not red neurons), which occur in conditions like gliosis or neurodegenerative diseases .
“Which CNS cells myelinate multiple axons, unlike their PNS counterparts?”
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Tags:
2020
Which of the following regarding oligodendroglia is true?
Oligodendroglia (Oligodendrocytes) are specialized glial cells of the central nervous system (CNS) responsible for myelination of axons .
A single oligodendrocyte can myelinate multiple axons (typically 30–50 internodes ), unlike Schwann cells , which only myelinate one axon per cell in the PNS .
Why the Other Options Are Wrong:
Helps in forming pia meningeal layer: ❌
The pia mater is part of the meninges , which arise from mesoderm , not neuroglia. Oligodendrocytes do not contribute to meningeal formation.
Supporting cells of PNS: ❌
Oligodendrocytes function only in the CNS .
Schwann cells , not oligodendrocytes, provide myelination in the peripheral nervous system (PNS) .
Helps in blood-brain barrier formation/maintenance: ❌
Astrocytes , not oligodendrocytes, contribute to the blood-brain barrier (BBB) by forming the glial end-feet around blood vessels.
Phagocytic cells: ❌
Microglia , not oligodendrocytes, are the resident macrophages of the CNS and have phagocytic activity.
“This structure, found in the spinal cord’s central region, is rich in unmyelinated axons, dendrites, and synapses, allowing for neural processing.”
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Tags:
2020
Where is the neuropil of the spinal cord most abundant?
The neuropil of the spinal cord is most abundant in the gray matter . Neuropil refers to the dense network of unmyelinated axons, dendrites, and glial cell processes that surround neuronal cell bodies. It is the primary site for synaptic connections and neuronal processing .
Key Features of Neuropil in the Gray Matter:
Found between neurons , serving as a site for synapses and interneuronal communication .
Composed of unmyelinated axons, dendrites, and glial cells , but few neuronal cell bodies .
Plays a role in sensory processing, reflex activity, and integration of motor responses .
Most abundant in the dorsal horn , where sensory processing occurs.
Why the Other Options Are Wrong:
Perikarya (✗) [Neuronal Cell Bodies, Not Neuropil]
Perikarya (soma) refer to neuron cell bodies , which are surrounded by neuropil but do not constitute neuropil themselves.
Synapsis (✗) [Synapses Are Part of Neuropil, But Not Its Main Component]
Synapses occur within the neuropil , but neuropil is not made exclusively of synapses .
Neuropil includes dendrites, unmyelinated axons, and glial processes , not just synaptic junctions.
Neuroglia (✗) [Glial Cells Are Present, But Not the Main Component]
Neuroglia (astrocytes, oligodendrocytes, microglia) support the neuropil but do not make up the majority of its structure .
Unmyelinated Axons (✗) [Present, But Not the Sole Component of Neuropil]
Neuropil contains unmyelinated axons , but also dendrites and glial cells .
The term neuropil refers to all synaptic connections and their supporting structures , not just axons.
Think about where dense synaptic interactions occur in the cerebellum . This structure is a key site for sensory input processing and contains inhibitory interneurons that regulate signal flow before reaching the Purkinje cells . Would this be in the outermost layer , where mainly dendrites and parallel fibers exist, or in a deeper layer with synaptic clusters?
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This glial cell type in the PNS wraps around one internode of one axon , unlike its CNS counterpart , which myelinates multiple axons.
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Tags:
2020
About the myelin sheath of the peripheral nerve, which of the following is correct?
The myelin sheath in the peripheral nervous system (PNS) is produced by Schwann cells , which wrap around axons to increase conduction velocity by allowing saltatory conduction between Nodes of Ranvier .
In the PNS , each Schwann cell myelinates only one internode of one axon .
In the central nervous system (CNS) , oligodendrocytes myelinate multiple axons at once.
Why the Other Options Are Incorrect?
In the central nervous system, myelinating cells myelinate several internodes of different axons ❌
True for CNS, but the question asks about the peripheral nerve .
Oligodendrocytes , not Schwann cells, myelinate multiple axons in the CNS .
It is produced by oligodendrocytes ❌
Oligodendrocytes produce myelin in the CNS, not the PNS .
It is produced by microglia ❌
Microglia are immune cells of the CNS , involved in phagocytosis and inflammation , not myelination.
In the peripheral nervous system, myelinating cells myelinate only one internode ❌
This is a tricky option because each Schwann cell myelinates only one internode .
However, the phrase “myelinating cells” might imply multiple Schwann cells working together, which could be misleading.
The most precise and correct answer remains : “It is produced by Schwann cells.”
These eosinophilic inclusions are characteristically found in chronic gliosis and certain brain tumors , often associated with astrocytes rather than neurons .
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Tags:
2021
In chronic gliosis, elongated, brightly eosinophilic protein aggregates within astrocyte processes are formed. What are they termed as?
Rosenthal fibers are elongated, brightly eosinophilic protein aggregates that accumulate within astrocyte processes in conditions involving chronic gliosis . These fibers are composed of:
Glial fibrillary acidic protein (GFAP)
Ubiquitin
Heat shock proteins (HSPs)
They are commonly seen in:
Chronic gliosis (reactive astrocytosis in response to brain injury)
Pilocytic astrocytomas (a type of low-grade brain tumor)
Alexander disease (a rare leukodystrophy affecting astrocytes)
Why the other options are incorrect:
Nissl bodies:
Nissl bodies are clusters of rough endoplasmic reticulum (RER) and ribosomes found in neurons , not astrocytes.
They are involved in protein synthesis , not gliosis.
None of these:
Incorrect, because Rosenthal fibers are a well-documented histopathological feature of chronic gliosis .
Microglial granules:
Microglia are the immune cells of the CNS , and they form granular bodies in response to infection, neurodegeneration, or injury , but these are not associated with astrocytes or gliosis .
Fibrillary astrocytes:
Fibrillary astrocytes are a type of reactive astrocyte seen in gliosis, but they do not refer to the eosinophilic inclusions seen in Rosenthal fibers.
Focus on the outermost layer of the cerebral cortex, known for its sparse neuronal content and rare specialized horizontal cells.
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This structure is heavily involved in protein synthesis and is stained basophilic due to its high RNA content .
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“Which brainstem structure contains sensory nuclei for fine touch and proprioception from the limbs?”
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Tags:
2020
Gracilis and cuneatus tubercles are seen on the surface of which of the following?
The gracile tubercle and cuneate tubercle are surface landmarks found on the dorsal (posterior) aspect of the medulla oblongata .
These structures contain the gracile nucleus and cuneate nucleus , which are part of the dorsal column–medial lemniscus (DCML) pathway , responsible for fine touch, vibration, and proprioception .
Function of Each Tubercle:
✔ Gracile tubercle → Contains the gracile nucleus , which processes sensory information from the lower limbs .
✔ Cuneate tubercle → Contains the cuneate nucleus , which processes sensory information from the upper limbs .
Why the Other Options Are Wrong:
Pons ❌
The pons contains the pontine nuclei, cranial nerve nuclei, and transverse pontine fibers but does not have gracile or cuneate tubercles .
Cerebellum ❌
The cerebellum is involved in coordination and balance , and it lacks gracile and cuneate tubercles.
Spinal Cord ❌
The gracile and cuneate fasciculi (tracts carrying sensory information) are present in the spinal cord , but the tubercles (containing the nuclei) are only in the medulla .
Midbrain ❌
The midbrain contains structures like the superior and inferior colliculi, cerebral peduncles, and substantia nigra , but no gracile or cuneate tubercles.
These cells are responsible for myelination outside the brain and spinal cord, helping in nerve regeneration after injury.
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Tags:
2019
Which of the following statements is correct regarding the Schwann cells?
Schwann cells are glial cells that are responsible for the myelination of axons in the peripheral nervous system (PNS) . Each Schwann cell wraps around a single axon segment, providing insulation and increasing the speed of nerve impulse conduction through saltatory conduction .
🔹 Key Features of Schwann Cells:
Found in the PNS
Myelinate one axon segment per Schwann cell
Aid in nerve regeneration after injury
This makes the statement “They are produced in the peripheral nervous system” correct.
Why Others Are Incorrect?
❌ One Schwann cell covers 30 nerve fibers:
Incorrect because each Schwann cell myelinates only one axon segment .
In contrast, oligodendrocytes (CNS glial cells) can myelinate multiple axons .
❌ They are produced in the central nervous system:
Incorrect because Schwann cells are in the PNS .
Oligodendrocytes are the CNS myelinating cells.
❌ Multiple sclerosis is a demyelinating disorder that affects the Schwann cells:
Incorrect because MS affects the CNS (oligodendrocytes), not Schwann cells .
Guillain-Barré syndrome (GBS) is a demyelinating disease of the PNS , affecting Schwann cells.
❌ Schwann cells cover all cranial nerves:
Incorrect because some cranial nerves (like the optic nerve) are myelinated by oligodendrocytes (since they are part of the CNS).
Schwann cells only myelinate peripheral cranial nerves (e.g., CN III–XII).
One of these cells is placed in the wrong layer. This interneuron is actually found in the molecular layer but is mistakenly listed in the granular layer .
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Which type of neuron is commonly found in the sensory organs responsible for hearing, balance, and vision?
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Tags:
2020
Under the morphological classification of the neurons, the bipolar neurons are the ones that bear a single axon and a single dendrite that emerges from the opposite poles of the spindle-shaped body. Which one of the following is an example of a bipolar neuron?
Bipolar neurons have one axon and one dendrite emerging from opposite poles of a spindle-shaped cell body .
These neurons are specialized sensory neurons found in:
Retina (in the eye)
Olfactory epithelium (smell receptors)
Cochlear and vestibular ganglia (hearing and balance in the inner ear)
Why the Other Options Are Wrong:
Purkinje cells of the cerebral cortex ❌
Incorrect , because Purkinje cells are multipolar neurons (having multiple dendrites and a single axon).
They are large inhibitory neurons found in the cerebellar cortex , not the cerebral cortex.
Dorsal root ganglion of the spinal nerves ❌
Incorrect , because neurons in the dorsal root ganglia are pseudounipolar , not bipolar.
They have a single process that splits into two branches (one going to the periphery, the other to the spinal cord).
Sensory ganglia of cranial nerves ❌
Incorrect , because sensory neurons in cranial nerve ganglia (e.g., trigeminal ganglion) are also pseudounipolar , not bipolar.
Mesencephalic nucleus of the trigeminal nerve ❌
Incorrect , because neurons in the mesencephalic nucleus are pseudounipolar , not bipolar.
These neurons relay proprioceptive information from the muscles of mastication.
Think about how sensory and motor signals travel—where would you expect to find neurons responsible for processing movement versus receiving sensory input?
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Focus on the specific functions of each connective tissue layer in a nerve.
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These are the largest neurons in the brain, responsible for voluntary movements. They reside in the motor cortex and send their axons all the way to the spinal cord.”
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Tags:
2020
Which is NOT true about Betz cells?
Betz cells are large pyramidal neurons found in the primary motor cortex (Brodmann area 4) . They are crucial for voluntary motor control as their axons form part of the corticospinal tract , which transmits motor signals from the brain to the spinal cord.
Key Facts about Betz Cells:
Located in Layer V (5th layer) of the cerebral cortex – specifically in the internal pyramidal layer .
Largest neurons in the CNS – they are giant pyramidal cells , with large somas and extensive dendritic trees .
Axons contribute to the corticospinal tract , facilitating voluntary motor movement .
Why the Other Options Are Correct:
They are present in the 5th layer of the cerebral cortex → ✅ Correct
Betz cells are in Layer V (internal pyramidal layer) , which is responsible for motor output.
This layer contains large pyramidal neurons , including Betz cells, that send descending motor commands to the spinal cord.
Their axons pass to the spinal cord as corticospinal fibers → ✅ Correct
Betz cells give rise to long axons that contribute to the corticospinal tract , which controls voluntary movement .
These fibers decussate (cross over) in the medulla (pyramidal decussation) before synapsing in the spinal cord.
Largest cells of the central nervous system → ✅ Correct
Betz cells are the largest neurons by soma size in the CNS, with extensive dendritic trees.
While Purkinje cells of the cerebellum have more dendritic branching, Betz cells have the largest cell bodies .
None of these → ❌ Incorrect
Since the statement about Betz cells being in the 6th layer is false, “None of these” is incorrect.
These cells act as nourishers and protectors of neurons, providing structural and metabolic support, especially in response to injury.
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The glial cell responsible for myelination in the PNS wraps around only one internode of a single axon , unlike its CNS counterpart.
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Tags:
2020
Regarding myelination in peripheral nervous system, what is the correct statement?
In the peripheral nervous system (PNS) , myelination is carried out by Schwann cells , which wrap around a single axon to form a myelin sheath . This insulating layer enhances action potential conduction velocity by enabling saltatory conduction between Nodes of Ranvier .
Each Schwann cell myelinates only one internode of one axon , unlike oligodendrocytes in the CNS , which can myelinate multiple axons.
Why the Other Options Are Incorrect?
Myelinating fibers have slow conduction velocity ❌
False , because myelination increases conduction velocity via saltatory conduction (action potentials jump between Nodes of Ranvier).
Unmyelinated fibers have slow conduction velocity .
It is also produced by fibroblasts as well ❌
False , because fibroblasts are involved in connective tissue support and extracellular matrix production , not myelination.
A Schwann cell can myelinate up to 30 axons ❌
False , because each Schwann cell myelinates only one internode of one axon in the PNS.
Oligodendrocytes in the CNS can myelinate multiple axons.
Oligodendrocytes are myelinating cells of the peripheral nervous system ❌
False , because oligodendrocytes myelinate axons in the CNS, not the PNS .
Schwann cells are exclusive to the PNS .
:
🧠 “Are sensory neurons typically multipolar or pseudounipolar?”
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Tags:
2021
Which of the following options is incorrectly matched?
Explanation:
Multipolar neurons are motor neurons and interneurons , primarily found in the ventral horn of the spinal cord , motor nuclei of cranial nerves, and throughout the central nervous system (CNS) .
Sensory neurons (found in the dorsal root ganglia and dorsal nuclei ) are typically pseudounipolar, not multipolar .
Therefore, the pairing “Multipolar Neurons – sensory and dorsal nuclei” is incorrect .
Why the Other Options Are Correct:
✔ 1. “Bipolar neurons – special senses” – Correct
Bipolar neurons are found in special sensory pathways , including:
Retina (vision)
Olfactory epithelium (smell)
Vestibulocochlear system (hearing and balance)
✔ 2. “Betz cell – motor activity” – Correct
Betz cells are large pyramidal neurons found in layer V of the primary motor cortex (Brodmann area 4).
They are responsible for motor control by sending impulses via the corticospinal tract to the spinal cord .
✔ 3. “Pseudo unipolar – dorsal root ganglia” – Correct
Pseudounipolar neurons are sensory neurons found in the dorsal root ganglia (DRG) .
They have a single process that splits into a central and peripheral branch , carrying sensory input to the CNS .
✔ 4. “Purkinje cells – cerebellar cortex” – Correct
Purkinje cells are large inhibitory neurons located in the cerebellar cortex .
They play a crucial role in coordinating movement by inhibiting deep cerebellar nuclei .
Think about the functional and anatomical differences between the cerebral cortex and the cerebellar cortex. Which type of neuron is unique to the cerebellum and not found in the cerebral cortex?
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“Which CNS cells require a constant oxygen and glucose supply and have limited regenerative ability?”
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Tags:
2020
Which one of the following are the most sensitive cells of the central nervous system?
Neurons are the most sensitive cells in the central nervous system (CNS) because they have high metabolic demands and rely on continuous oxygen and glucose supply.
Unlike glial cells, neurons have limited regenerative capacity and are highly susceptible to ischemia, hypoxia, toxins, and metabolic disturbances .
Neuronal death due to ischemia (stroke) or neurodegenerative diseases (e.g., Alzheimer’s, Parkinson’s) often leads to permanent loss of function .
Why the Other Options Are Wrong:
Renshaw Cells ❌
These are inhibitory interneurons in the spinal cord , regulating motor neuron activity via glycine release .
While important for motor control , they are not the most sensitive CNS cells.
Astrocytes ❌
Astrocytes play a key role in neuroprotection, metabolism, and repair .
They are more resistant to damage than neurons and often proliferate in response to injury (reactive gliosis ).
Microglial Cells ❌
Microglia are immune cells of the CNS , responsible for phagocytosis and inflammation .
They are more resilient than neurons and become activated in response to injury or infection .
Schwann Cells ❌
Schwann cells belong to the peripheral nervous system (PNS) and form myelin around peripheral nerves .
They are not CNS cells , making this answer incorrect.
Some neurons have such intricate branching structures.. try to see if you can figure out intricate things in your life without leaving your comfort zone.
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This part of the brain looks white because it’s packed with myelinated nerve fibers , helping signals travel fast .
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Tags:
2022
Which of the following cell structures constitute the white matter of the central nervous system?
The white matter of the central nervous system (CNS) is primarily composed of:
✅ Myelinated axons → These transmit nerve signals over long distances.
✅ Glial cells → Mainly oligodendrocytes , which produce myelin, and astrocytes , which support neuronal function.
White matter appears white due to the high lipid content of myelin , which insulates axons and speeds up electrical transmission.
White Matter vs. Gray Matter:
White matter → Contains myelinated axons and glial cells but few or no cell bodies .
Gray matter → Contains neuronal cell bodies, dendrites, and synapses (e.g., cerebral cortex, basal ganglia).
Why not the other options?
Cell bodies only → Cell bodies are found in gray matter, not white matter .
Axons and dendrites → Dendrites are mostly in gray matter , where synapses occur.
Cell bodies and dendrites → This describes gray matter , not white matter.
Axons only → White matter also contains glial cells , particularly oligodendrocytes.
Thus, the correct answer is “Axons and glial cells,” as these are the main components of white matter in the CNS.
Think about the layers of connective tissue in a peripheral nerve and their specific roles. Which layer is responsible for enclosing bundles of nerve fibers
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Tags:
2020
Which one of the following is the histological feature of a peripheral nerve?
The histological structure of a peripheral nerve includes three layers of connective tissue:
Endoneurium: A thin layer of connective tissue surrounding individual nerve fibers (axons and their Schwann cells).
Perineurium: A dense, collagenous sheath that surrounds each fascicle (a bundle of nerve fibers). This layer provides structural support and acts as a diffusion barrier.
Epineurium: The outermost layer of connective tissue that surrounds the entire nerve, including multiple fascicles. It is thicker and less regular than the perineurium.
Thus, the statement that each fascicle is invested by a collagenous covering called the perineurium is correct.
Why the Other Options Are Wrong:
Epineurium is a thin, regular collagenous coat:
This is incorrect because the epineurium is thick and irregular , not thin and regular.
Around Schwann cells is a thin layer called the perineurium, consisting of reticular fibers:
This is incorrect because the perineurium surrounds fascicles , not individual Schwann cells. The layer around Schwann cells is the endoneurium , which contains reticular fibers.
Epineurium does not extend deeply to fill the space between fascicles:
This is incorrect because the epineurium does extend between fascicles, filling the space around them.
Axons and Schwann cells are not enclosed within layers of connective tissue:
This is incorrect because axons and Schwann cells are enclosed by the endoneurium , which is a layer of connective tissue.
“The brain needs protection from harmful substances while still allowing essential nutrients in. This barrier is not a single structure but a combination of different elements working together. What could these be?”
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Tags:
2019
The blood-brain barrier is formed by which of the following?
The blood-brain barrier (BBB) is a highly selective barrier that protects the brain from toxins, pathogens, and fluctuations in systemic blood composition while allowing essential nutrients to pass through. It is composed of multiple structures working together to maintain CNS homeostasis.
Correct Answer: All of These
Why is “All of These” the Correct Answer?
The BBB is formed by several key components :
Tight Junctions Between Capillary Endothelial Cells
The capillary endothelial cells in the brain have tight junctions (zonula occludens), preventing the paracellular movement of substances.
These junctions force molecules to pass through the endothelial cells (transcellular transport ) instead of between them, creating a highly selective barrier .
Pericytes Present Around the Capillaries
Pericytes are contractile cells that wrap around capillaries , regulating blood flow and barrier integrity .
They help control the permeability of the BBB and play a role in the immune response within the CNS.
The Impermeable, Non-Fenestrated, Basement Membrane of the Capillaries
The capillary basement membrane is continuous and non-fenestrated , acting as a mechanical and biochemical barrier that prevents large molecules and pathogens from entering the CNS.
Pseudopods of the Astrocytes
Astrocyte foot processes (pseudopods) surround the capillaries and release signals that maintain and regulate the integrity of the BBB .
They help in nutrient transport , repair, and modulation of neurovascular coupling .
Since all of these components collectively contribute to the BBB , the correct answer is “All of These.”
Why Are the Other Individual Options Incorrect on Their Own?
Each option represents an essential component of the BBB, but the barrier is not formed by just one of them alone —it is a combination of all these structures that provides the selective permeability characteristic of the BBB.
This type of cell is primarily found in the cerebral cortex, and it has a characteristic shape with a pyramid-like body and long dendrites.
34 / 41
could evolutionary older regions have a different structure?
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“In the CNS, one cell can myelinate many axons—what is it called?”
36 / 41
Tags:
2021
The myelin sheath in the central nervous system is made of which of the following?
In the central nervous system (CNS) , the myelin sheath is produced by oligodendrocytes . Myelin is a fatty insulating layer that wraps around axons, increasing the speed of nerve impulse conduction by enabling saltatory conduction between the nodes of Ranvier .
Each oligodendrocyte can myelinate multiple axons , unlike Schwann cells , which myelinate only one axon in the peripheral nervous system (PNS) .
Why the Other Options Are Wrong:
Schwann cells – These produce myelin in the peripheral nervous system (PNS) , not the CNS.
Astrocytes – These are support cells in the CNS that help in blood-brain barrier maintenance , nutrient transport, and repair, but they do not produce myelin .
Microglia – These are the resident immune cells of the CNS, acting as macrophages to remove debris and pathogens. They have no role in myelination.
Ependymal cells – These line the ventricles of the brain and the central canal of the spinal cord , producing cerebrospinal fluid (CSF) , but they do not form myelin.
Some cellular structures are more elusive under standard lab techniques
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Tags:
2020
Which of the following is NOT shown by the neuroglial cells?
Neuroglial cells (glial cells) are supporting cells of the CNS that provide structural, metabolic, and immune support to neurons.
They include astrocytes, oligodendrocytes, microglia, and ependymal cells .
Unlike neurons, most neuroglial cells do not stain well with routine H&E staining because they have small nuclei and minimal cytoplasm .
Special stains like GFAP (glial fibrillary acidic protein) for astrocytes and silver or immunohistochemical stains are needed for better visualization.
Why the Other Options Are Correct:
Capable to divide through life: ✅ Correct
Unlike neurons, glial cells retain the ability to divide throughout life. This is why gliomas (brain tumors) are common, but primary neuronal tumors are rare .
They are non-neuronal cells of CNS: ✅ Correct
Glial cells are not neurons ; they provide support and insulation to neurons.
Arise mostly from neuroectoderm: ✅ Correct
Most neuroglial cells (astrocytes, oligodendrocytes, and ependymal cells ) arise from the neuroectoderm . Microglia , however, arise from the mesoderm (monocyte lineage).
They are five to ten times more abundant than neurons: ✅ Correct
Glial cells vastly outnumber neurons, with a ratio of approximately 5:1 to 10:1 in the CNS.
“Which glial cell plays a key role in maintaining the selective permeability of the brain’s protective barrier?”
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Focus on the output neurons of the cerebellar cortex and the type of interneurons that regulate their activity by targeting the soma.
39 / 41
Focus on the role of oligodendrocytes in the CNS. Remember that they are involved in myelination and can myelinate multiple axons, unlike Schwann cells in the PNS.
40 / 41
“This type of neuron is a major excitatory cell in the cerebral cortex but is not part of the cerebellum’s architecture.”
41 / 41
Tags:
2019
Which types of cells are not present in the cerebellar cortex?
Understanding the Cellular Composition of the Cerebellar Cortex
The cerebellar cortex consists of three layers:
Molecular Layer (Outer Layer)
Contains stellate cells and basket cells (both inhibitory interneurons).
Contains the dendrites of Purkinje cells and parallel fibers of granule cells .
Purkinje Layer (Middle Layer)
Contains Purkinje cells , which are the sole output neurons of the cerebellar cortex.
Granular Layer (Inner Layer)
Contains granule cells and Golgi cells .
Granule cells are the only excitatory neurons in the cerebellar cortex.
Why the Correct Answer is Right
✅ Pyramidal cells are NOT present in the cerebellar cortex.
Pyramidal cells are excitatory neurons found in the cerebral cortex , particularly in the motor and association areas .
They are NOT part of the cerebellar cortex , which is primarily composed of Purkinje cells and interneurons .
Why the Other Options Are Incorrect (These Cells Are Present in the Cerebellar Cortex)
Stellate cells – Present in the molecular layer ; inhibitory interneurons.
Golgi cells – Present in the granular layer ; inhibitory interneurons that regulate granule cells.
Granule cells – Present in the granular layer ; the only excitatory neurons in the cerebellar cortex.
Basket cells – Present in the molecular layer ; inhibitory interneurons that modulate Purkinje cells.
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