Glial Cells of the Nervous System

Question 1

Are there more glia or neurons in the nervous system?

Answer 1

glia, by a ratio of 3 to 1

Question 2

What are glia cells?

Answer 2

cells which form a critical support network for neurons

Question 3

What does glia mean in Greek?

Answer 3

Glue

This reflects the presumption that these cells “held the nervous system together”

Question 4

Glia are categorized by what 2 things?

Answer 4

size and function

Question 5

Large glia cells are called ____ and small glia cells are called ____.

Answer 5

macroglia

microglia

Question 6

What are the 3 types of macroglia?

Answer 6

• Astrocytes
• Oligodendrocytes
• Schwann cells

Question 7

What are astrocytes?

Answer 7

Star-shaped macroglial cells found throughout the CNS and have a direct role in cell signaling

Question 8

Where can astrocytes be found in the CNS and why?

Answer 8

Gray matter because of close association with neuronal cell bodies, dendrites, and synapses

Question 9

What 3 ways can astrocytes be signaled?

Answer 9

By signals from…

• adjacent neurons
• mechanical changes

Question 10

What do stimulated astrocytes do?

Answer 10

Spread waves of Ca2+ to neighboring astrocytes through gap junctions

Question 11

Do astrocytes have synapses or generate action potentials?

Answer 11

No, even thought they have NTs

Question 12

In what 3 ways do astrocytes act as scavengers?

Answer 12

• they take up extra K+ ions in the extracellular environment, which helps regulate the ionic concentration gradient
• they remove chemical transmitters from the synaptic cleft between neurons
• they clean up other debris in the extracellular space

Question 13

What are 3 other things astrocytes do?

Answer 13

• ssist in formation of new synapses and circuits
• form the blood-brain barrier
• participate in the formation of scars to fill in cavities that have been cleared of neural tissues following an injury

Question 14

Astrocytes connect neurons and blood capillaries via what structures?

Answer 14

end-feet

Question 15

Oligodendrocytes and Schwann cells form what?

Answer 15

the myelin sheath

Question 16

Oligodendrocytes myelinate neurons of the _____ nervous system

Answer 16

central

Question 17

Schwann cells myelinate neurons of the _____ nervous system

Answer 17

peripheral

Question 18

When is an axon considered myelinated?

Answer 18

When it is completely encased by myelin. If the axon is partially covered it is considered unmyelinated

Question 19

Microglial cells typically function as what?

Answer 19

phagocytes: they act as the immune system of the CNS and clean the neural environment

Question 20

When are microglia activated?

Answer 20

During nervous system development and following injury, infection, or disease

Question 21

How do microglial cells assist in healing?

Answer 21

When cells die they secrete proteins that attract microglia into the site. They then clean up and remove debris from the dying cells

Question 22

4 Characteristics of Glial Stem Cells

Answer 22

• self-renew
• differentiate into most types of glial cells and neurons
• populate developing and degenerating regions of the CNS

Question 23

Demyelination of neurons in the PNS is called what?

Answer 23

Guillain-Barre syndrome

Question 24

What age group does Guillain-Barre Syndrome affect?

Answer 24

Affects all ages, however people from the ages of 30-50 are the most commonly affected

Question 25

Is there a gender differentiation for Guillain-Barre Syndrome?

Answer 25

No. Affects both sexes equally

Question 26

What is the incidence of Guillain-Barre Syndrome?

Answer 26

1.3 per 100,000 people per year

Question 27

What are a few signs and symptoms of Guillain-Barre Syndrome?

Answer 27

- Abnormal sensations (tingling, burning) - Pain - BP fluctuation - Irregular cardiac rhythms - Paralysis (may include respiratory muscles) - Impaired eye and facial movements, chewing, swallowing

Question 28

Demyelination of neurons in the CNS is called what?

Answer 28

Multiple Sclerosis

Question 29

What age group does Multiple Sclerosis affect?

Answer 29

Typical age onset is 20-40 years

Question 30

What is the incidence of Multiple Sclerosis?

Answer 30

100 per 100,000 people per year | 2.5 million affected worldwide

Question 31

What are a few signs and symptoms of Multiple Sclerosis?

Answer 31

- Abnormal sensations (tingling, numbness, pins and needles) - Bladder disorders - Sexual impotence in men - Genital anesthesia in women - Weakness, incoordination, reflex changes - Partial blindness in one eye, double vision, eye movement disorders

Question 32

What are glial stem cells and where can they be found?

Answer 32

Glial stem cells are immature and undifferentiated cells found throughout the adult brain which retain the capacity to proliferate and generate differentiated glia and, in some cases, neurons.

Question 33

What is neuroinflammation?

Answer 33

the response of the CNS to infections, diseases and injuries

Question 34

What are the benefits of neuroinflammation?

Answer 34

It initiates the of microglia and astrocytes. The microglia remove debris, produce neurotrophic factors that support axonal regeneration and remyelination. The astrocytes reseal the blood-brain barrier and provide trophic support.

Question 35

What are the disadvantages of neuroinflammation?

Answer 35

It can cause the death of neurons and oligodendrocytes and inhibit neural regeneration

Question 36

There is a correlation between abnormal glial activity and what pathologies?

Answer 36

- stroke - Alzheimer’s disease - Parkinson’s disease - multiple sclerosis

Question 37

Demyelination of peripheral nerves results in what?

Answer 37

Disrupted proprioception (awareness of limb position) and weakness

Question 38

What is Guillain-Barré Syndrome?

Answer 38

Acute inflammation and demyelination of peripheral sensory and motor fibers

Question 39

When does Guillain-Barré Syndrome occur?

Answer 39

Occurs 2 to 3 weeks after a mild infection in which the persons immune system generates antibodies that attack Schwann cells

Question 40

In 2/3 of Guillain-Barré Syndrome cases it is preceded by what?

Answer 40

Intestinal infection that activates the immune system causing production of an antibody that mistakenly cross-reacts with the myelin sheath

Question 41

What are some signs and symptoms of Guillain-Barré Syndrome?

Answer 41

- decreased sensation and skeletal muscle paralysis - cranial nerves of the face may be affected, causing difficulty with chewing, swallowing, speaking, and facial expressions - most often report deep aching pain or hypersensitivity to touch

Question 42

Describe the onset and recovery period for Guillain-Barré Syndrome

Answer 42

Onset is rapid, but followed by plateau then gradual recovery. Recovery is usually complete.

Question 43

Medical treatment for Guillain-Barré Syndrome includes what?

Answer 43

plasmapheresis and intravenous immunoglobulin therapy

Question 44

What is plasmapheresis?

Answer 44

The process of filtering the blood plasma to remove the circulating antibodies responsible for attacking the antibodies associated with Guillain-Barré syndrome

Question 45

What is intravenous immunoglobulin therapy?

Answer 45

A form of therapy for Guillain-Barré syndrome that neutralizes specific antibodies and decreases inflammtion

Question 46

What is multiple sclerosis?

Answer 46

A disorder in which the immune system produces antibodies that attack oligodendrocytes, producing plaques in the white matter of the CNS

Question 47

What are some signs and symptoms of multiple sclerosis?

Answer 47

- weakness - lack of coordination - impaired vision - double vision - impaired sensation - slurred speech - disruption of memory and emotions are also possible

Question 48

Why is the diagnosis of MS difficult?

Answer 48

It usually manifests with one sign that may completely resolve

Question 49

The onset of MS is most common between what ages?

Answer 49

between 20 and 40 years

Question 50

What are the gender differences of those diagnosed with MS?

Answer 50

women are three times more frequently affected

Question 51

What are the 4 types of MS according to the course of disease progression?

Answer 51

- Relapsing/remitting - Secondary progressive - Primary progressive - Progressive relapsing

Question 52

Describe Relapsing/remitting MS

Answer 52

This type of MS begins with alternating relapses and remissions, in which relapses are characterized by new signs and symptoms and the worsening of old signs and symptoms

Question 53

Describe secondary progressive MS

Answer 53

Develops when relapsing/remitting MS goes untreated. This type of MS is distinguished by a continuous neurologic decline with fewer or no relapses.

Question 54

Describe primary progressive MS

Answer 54

There is a steady functional decline from time of onset with predominately spinal cord symptoms

Question 55

What percentage of cases progress to primary progressive MS?

Answer 55

10%

Question 56

Describe progressive relapsing MS

Answer 56

This type begins with a steady functional decline with superimposed relapses and partial remissions in which function is never fully recovered.

Question 57

What percentage of cases progress to progressive relapsing MS?

Answer 57

5%

Question 58

What types of things are MS patients encouraged to avoid and why?

Answer 58

Patients should avoid high temperatures and excessive exertion, because increases in body temperature are believed to interfere with the activity of membrane proteins in axons, further disabling action potential conduction

Question 59

What types of things are MS patients encouraged to incorporate into their lives?

Answer 59

Adequate vitamin D3, stress management, regular exercise and proper medical management to try to slow disease progression