Glial Cells of the Nervous System Flashcards
Are there more glia or neurons in the nervous system?
glia, by a ratio of 3 to 1
What are glia cells?
cells which form a critical support network for neurons
What does glia mean in Greek?
Glue
This reflects the presumption that these cells “held the nervous system together”
Glia are categorized by what 2 things?
size and function
Large glia cells are called ____ and small glia cells are called ____.
macroglia
microglia
What are the 3 types of macroglia?
- Astrocytes
- Oligodendrocytes
- Schwann cells
What are astrocytes?
Star-shaped macroglial cells found throughout the CNS and have a direct role in cell signaling
Where can astrocytes be found in the CNS and why?
Gray matter because of close association with neuronal cell bodies, dendrites, and synapses
What 3 ways can astrocytes be signaled?
By signals from…
- adjacent neurons
- mechanical changes
What do stimulated astrocytes do?
Spread waves of Ca2+ to neighboring astrocytes through gap junctions
Do astrocytes have synapses or generate action potentials?
No, even thought they have NTs
In what 3 ways do astrocytes act as scavengers?
- 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
What are 3 other things astrocytes do?
- 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
Astrocytes connect neurons and blood capillaries via what structures?
end-feet
Oligodendrocytes and Schwann cells form what?
the myelin sheath
Oligodendrocytes myelinate neurons of the _____ nervous system
central
Schwann cells myelinate neurons of the _____ nervous system
peripheral
When is an axon considered myelinated?
When it is completely encased by myelin. If the axon is partially covered it is considered unmyelinated
Microglial cells typically function as what?
phagocytes: they act as the immune system of the CNS and clean the neural environment
When are microglia activated?
During nervous system development and following injury, infection, or disease
How do microglial cells assist in healing?
When cells die they secrete proteins that attract microglia into the site. They then clean up and remove debris from the dying cells
4 Characteristics of Glial Stem Cells
- self-renew
- differentiate into most types of glial cells and neurons
- populate developing and degenerating regions of the CNS
Demyelination of neurons in the PNS is called what?
Guillain-Barre syndrome
What age group does Guillain-Barre Syndrome affect?
Affects all ages, however people from the ages of 30-50 are the most commonly affected
Is there a gender differentiation for Guillain-Barre Syndrome?
No. Affects both sexes equally
What is the incidence of Guillain-Barre Syndrome?
1.3 per 100,000 people per year
What are a few signs and symptoms of Guillain-Barre Syndrome?
- Abnormal sensations (tingling, burning)
- Pain
- BP fluctuation
- Irregular cardiac rhythms
- Paralysis (may include respiratory muscles)
- Impaired eye and facial movements, chewing, swallowing
Demyelination of neurons in the CNS is called what?
Multiple Sclerosis
What age group does Multiple Sclerosis affect?
Typical age onset is 20-40 years
What is the incidence of Multiple Sclerosis?
100 per 100,000 people per year
2.5 million affected worldwide
What are a few signs and symptoms of Multiple Sclerosis?
- 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
What are glial stem cells and where can they be found?
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.
What is neuroinflammation?
the response of the CNS to infections, diseases and injuries
What are the benefits of neuroinflammation?
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.
What are the disadvantages of neuroinflammation?
It can cause the death of neurons and oligodendrocytes and inhibit neural regeneration
There is a correlation between abnormal glial activity and what pathologies?
- stroke
- Alzheimer’s disease
- Parkinson’s disease
- multiple sclerosis
Demyelination of peripheral nerves results in what?
Disrupted proprioception (awareness of limb position) and weakness
What is Guillain-Barré Syndrome?
Acute inflammation and demyelination of peripheral sensory and motor fibers
When does Guillain-Barré Syndrome occur?
Occurs 2 to 3 weeks after a mild infection in which the persons immune system generates antibodies that attack Schwann cells
In 2/3 of Guillain-Barré Syndrome cases it is preceded by what?
Intestinal infection that activates the immune system causing production of an antibody that mistakenly cross-reacts with the myelin sheath
What are some signs and symptoms of Guillain-Barré Syndrome?
- 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
Describe the onset and recovery period for Guillain-Barré Syndrome
Onset is rapid, but followed by plateau then gradual recovery.
Recovery is usually complete.
Medical treatment for Guillain-Barré Syndrome includes what?
plasmapheresis and intravenous immunoglobulin therapy
What is plasmapheresis?
The process of filtering the blood plasma to remove the circulating antibodies responsible for attacking the antibodies associated with Guillain-Barré syndrome
What is intravenous immunoglobulin therapy?
A form of therapy for Guillain-Barré syndrome that neutralizes specific antibodies and decreases inflammtion
What is multiple sclerosis?
A disorder in which the immune system produces antibodies that attack oligodendrocytes, producing plaques in the white matter of the CNS
What are some signs and symptoms of multiple sclerosis?
- weakness
- lack of coordination
- impaired vision
- double vision
- impaired sensation
- slurred speech
- disruption of memory and emotions are also possible
Why is the diagnosis of MS difficult?
It usually manifests with one sign that may completely resolve
The onset of MS is most common between what ages?
between 20 and 40 years
What are the gender differences of those diagnosed with MS?
women are three times more frequently affected
What are the 4 types of MS according to the course of disease progression?
- Relapsing/remitting
- Secondary progressive
- Primary progressive
- Progressive relapsing
Describe Relapsing/remitting MS
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
Describe secondary progressive MS
Develops when relapsing/remitting MS goes untreated. This type of MS is distinguished by a continuous neurologic decline with fewer or no relapses.
Describe primary progressive MS
There is a steady functional decline from time of onset with predominately spinal cord symptoms
What percentage of cases progress to primary progressive MS?
10%
Describe progressive relapsing MS
This type begins with a steady functional decline with superimposed relapses and partial remissions in which function is never fully recovered.
What percentage of cases progress to progressive relapsing MS?
5%
What types of things are MS patients encouraged to avoid and why?
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
What types of things are MS patients encouraged to incorporate into their lives?
Adequate vitamin D3, stress management, regular exercise and proper medical management to try to slow disease progression
