myelination

Question 1

What is myelin?

Answer 1

Insulating lipid layer (sheath) that surrounds some axons

Myelin is formed by the wrapping of cell membrane with glial cells during the process of myelination.

Question 2

What types of cells are responsible for myelination in the CNS?

Answer 2

Oligodendrocytes

Oligodendrocytes can myelinate multiple axons simultaneously.

Question 3

What types of cells are responsible for myelination in the PNS?

Answer 3

Schwann cells

Each Schwann cell myelinates a single axon.

Question 4

What are the Nodes of Ranvier?

Answer 4

Gaps between two adjacent myelin segments, approximately 1 µm long

At these nodes, the axon is exposed to the extracellular space and contains a high concentration of voltage-gated Na+ channels.

Question 5

How does myelin affect action potential conduction speed?

Answer 5

Increases speed and efficiency of action potential propagation

This is due to saltatory conduction and reduced leakage of local current in internodal regions.

Question 6

What is the effect of increasing axon diameter on action potential propagation?

Answer 6

Decreases axial resistance, increasing speed of propagation

A larger diameter allows for faster conduction of action potentials.

Question 7

What is the relationship between myelin sheath and membrane resistance?

Answer 7

Adding myelin sheath increases membrane resistance and decreases capacitance

This improves the efficiency of action potential conduction.

Question 8

What is Multiple Sclerosis (MS)?

Answer 8

A degenerative demyelinating disease of the CNS

It is likely an autoimmune disorder where the immune system attacks myelin proteins.

Question 9

onset age and gender of MS, are symptoms persistent?

Answer 9

Variable among individuals, onset typically between 20-40 years old, more common in women

85% of cases are relapse-remitting, where symptoms come and go.

Question 10

What are the associated issues in MS?

Answer 10

• Damaged myelin and loss of glial support
• Axonal loss
• Inflammation
• Abnormal and eventual loss of action potential conduction

These factors contribute to the progression of the disease.

Question 11

How is MS diagnosed?

Answer 11

• MRI (magnetic resonance imaging)
• Lumbar puncture (CSF tested for abnormal number of immune cells and antibodies)

These diagnostic methods help confirm the presence of MS.

Question 12

What types of treatments are available for MS?

Answer 12

• Drugs that prevent relapse and progression (e.g., glatiramer acetate)
• Immunosuppressant drugs

Glatiramer acetate acts as an immune ‘decoy’ to redirect the immune response away from myelin.

Question 13

MS symtoms and areas affected

Answer 13

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