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Nervous System Histology and Myelination
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1
Question
What are the three fundamental properties of nerve cells?
Answer
Excitability, conductibility, communicability.
2
Question
Name two other cell types present in nervous tissue besides neurons.
Answer
Glial cells and vascular elements.
3
Question
What are the three layers of the meninges, from outer to inner?
Answer
Dura mater, arachnoid, pia mater.
4
Question
What is the CSF and where is it found?
Answer
Cerebrospinal fluid (CSF); in ventricles and subarachnoid space.
5
Question
Where is CSF produced and what cells form its barrier?
Answer
Choroid plexuses; ependymal cells.
6
Question
What is the mechanical and nutritional role of CSF?
Answer
Nutrition and brain buoyancy (support/relief of weight).
7
Question
What are the two types of nerves?
Answer
Cranial nerves and spinal nerves.
8
Question
What structure surrounds fascicles within a nerve?
Answer
Perineurium.
9
Question
What is the role of glial cells in the nervous system?
Answer
Provide metabolic and structural support; non-excitable; can proliferate.
10
Question
Where is Schwann cell function restricted to in the nervous system?
Answer
Peripheral nervous system (PNS).
11
Question
What is the difference between myelinated and unmyelinated axons regarding Schwann cells?
Answer
Schwann cells myelinate axons in the PNS; can enwrap multiple unmyelinated axons or a single myelinated axon.
12
Question
What is the composition and role of the myelin sheath?
Answer
Lipid-rich layer wrapping axons to insulate and increase conduction speed.
13
Question
What are Schmidt-Lantermann incisures and their function?
Answer
Gaps allowing cytoplasm to access the myelin sheath, enabling renewal.
14
Question
What marks the external and internal mesaxons in Schwann cell–axon interactions?
Answer
External mesaxone and internal mesaxone defined during myelination.
15
Question
What structures define the dense line and major line in myelin structure?
Answer
Major dense line (intracellular membranes) and non-compact regions line.
16
Question
Where is the node of Ranvier located?
Answer
Between adjacent myelin segments along the axon.
17
Question
What are the cytoplasmic collars in myelinated segments?
Answer
Internal and external cytoplasmic collars surrounding the mesaxone.
18
Question
What is the role of PMP22 in myelination studies?
Answer
A myelin protein used as a target in immunohistochemistry.
19
Question
What is the role of Schmidt-Lantermann incisions in the myelin sheath?
Answer
They allow cytoplasm diffusion between layers, linking glial collars.
20
Question
Why is myelin considered a dynamic structure?
Answer
Because it undergoes continuous renewal.
21
Question
In a cross-section of a nerve, what dense electron structures correspond to myelin sheaths?
Answer
Myelin sheaths (compact myelin) appear as densely stained structures.
22
Question
What is the node of Ranvier?
Answer
A naked axonal segment between two Schwann cells.
23
Question
Where are Schwann cells located and what do they myelinate?
Answer
In the peripheral nervous system; they myelinate peripheral neurons.
24
Question
What is the functional consequence of myelin on membrane resistance and capacitance?
Answer
Increases resistance, decreases capacitance, and speeds saltatory conduction.
25
Question
What is saltatory conduction?
Answer
Action potential jumps from node to node along the myelinated axon.
26
Question
Which glial cell myelinates multiple axons in the central nervous system?
Answer
Oligodendrocyte.
27
Question
Which glial protein is commonly used to label myelin in immunohistochemistry?
Answer
MAG (myelin-associated glycoprotein).
28
Question
What are the main glial cell types described in the text for the CNS and PNS?
Answer
CNS: oligodendrocytes, astrocytes, ependymocytes, microglia; PNS: Schwann cells, satellite cells.
29
Question
Describe the key features of a Schwann cell in myelinated nerves as seen in histology.
Answer
Schwann cell nuclei with Schwann cell cytoplasm; multiple lamellae forming compact myelin; Schmidt-Lantermann incisures present.
30
Question
Where is myelin primarily visualized using Luxol blue staining?
Answer
In myelinated white matter of the CNS and in peripheral nerves.