Exam 1 Week 2: ppt 3 Neuroglia

Question 1

Four general functions of neruoglia

Answer 1

•Provide structural and metabolic support

1. –Physical structure of brain
2. –Maintain ionic stability
3. –Maintain glucose stability
4. –Help regulate neurotrophic factors & transmitters

Question 2

Do glia maintain their mitotic capacity?

Answer 2

YES!!!

Question 3

What are neuroglia classified by?

List the CNS neuroglia in their proper classification

Answer 3

Classified by size and structural geometry

• –Macroglia
  
  • Astrocytes
  • Oligodendroglia
• –Ependymal cells
• –Microglia

Question 4

Are there more neurons or glia?

Answer 4

You will hear that neuroglia greatly outnumber neurons. But from the work of Azevedo, et al (2009) the adult brain contains about equal numbers of neurons and glia.

(answer that neuroglia outnumber neurons for Dr. Shappy probably - we had that discussion in her class too)

Question 5

What is the largest glial cell?

Answer 5

astrocytes

Question 6

What is the most numerous glial cell?

Answer 6

astrocytes

Question 7

General descriptoin of Astorcytes:

Answer 7

Astrocytes are the Largest, most elaborate, and numerous glial cell They are Star shaped, with radiating processes and are often seen Interposed between capillaries and neurons

Their Stellate shape with numerous processes radiating from central cell body gives them their name. Traditionally thought to have roles in neural Structure and repair & protection and in the formation of the Blood-brain barrier But they do so much more . . . .

Question 8

Roles of Astrocytes: (10 with details for each)

Answer 8

So many things…

1. –Structural - physical framework supporting neurons (fibroblasts of the brain)
   
   • –Astrocytic end-feet encircling endothelial cells of blood vessels forming part of the blood-brain barrier (BBB).
     
     • –Tight endothelial junctions and basal lamina of capillary endothelium provide most of BBB so astrocytic feet probably of less significance than traditionally thought
2. –Metabolic support – providing
   
   • Storage area in the brain of free glucose as glycogen
   • Both glycogen synthesis & glycogenolysis
   • Can fuel neurons during periods of glucose shortage
   • §Storage of other micronutrients to maintain a consistent supply for neurons
   • §Important role in regulation of brain lactate
3. Regulation extracellular ion concentration
   
   • §Rapidly clear excess accumulation of K+ to regulate neuronal excitability
   • §Control extracellular Ca++ also affecting neuronal excitability & synaptic transmission
   • Propagate movement of Ca++ over long distances
4. Influence Neurotransmtters
   
   • Uptake of variety of transmitters regulating the extracellular concentrations of these transmitters, such as glutamate, ATP and GABA
   • –Release glutamate or ATP in a vesicular, Ca++ -dependent manner much like synaptic function to be discussed later
5. –May play role in regulating overall excitability of CNS
6. –Long-term potentiation:
   
   • Debate role in consolidation of learning and memory in the hippocampus
   • Modulate neuronal synaptic activity in hippocampal slices
   • But some question role in modulating synaptic plasticity in vivo
7. –Repair/inhibition of damaged neural tissue
   
   • Release of factors that stimulate microglia activity
   • But glial or astrocytic scarring may block regeneration of severed axons
   • Also Release of factors that block regenerative growth of damaged axons
8. –Vasomodulation
   
   • may serve as intermediary in neuronal regulation of cerebral blood flow
9. –Promote myelination by oligodendroglia
   
   • Mediate ATP promotion the myelinating activity of oligodendrocytes

Question 9

What are Oligodendorcytes?

Answer 9

Oligodendroglia are responsible for the Formation and maintenance of myelin sheaths of CNS axons. Oligodendrocytes send out long protoplasmic processes that wrap around neuronal axons Since Multiple glial cells myelinate a single CNS axon the myelin sheath is discontinuous along the axon interrupted at nodes of Ranvier

Each oligodendrocyte has Numerous cytoplasmic processes so a single oligodendrocyte can myelinate segments of some 7–70 axons – as you might expect they are most Abundant in white matter through the CNS

Question 10

wHat are microglia?

Answer 10

Microglia represent about 10–20% of all glial cells. They are Highly mobile immune cells of the CNS and function much like macrophages do in the rest of the body. They are very important as the first response to damage in the CNS as the BBB prevents or slows entry of neutrophils & monocytes into CNS Mictoglial cells are widely Distributed through CNS & particularly abundant in gray matter

Question 11

3 basic Microglial roles?

Answer 11

1. –Defense against infection
2. –Scavenging - removal of damaged neural & glial material prior to repair
3. –Chronic CNS inflammation

Question 12

Microglial roles in Alsheimer’s disease

Answer 12

1. –Neurofibrillary tangles & amyloid plaques
2. –Activated microglia over-expressing IL-1 leading to excessive tau phosphorylation
3. –Synthesis amyloid precursor protein (APP) which can form amyloid plaques of membrane bound APP

Microglial cells may also have Roles in Alzheimer’s disease and other degenerative diseases of the nervous system. Seen in high concentration with these conditions. Neurofibrillary tangles & amyloid plaques are associated with several neuro degenerative diseases. It is known that Activated microglia over-expressing IL-1 leading to excessive tau phosphorylation which forms the neurofilbilary tangles. Microglia are also replated to the Synthesis amyloid precursor protein (APP) which can form amyloid plaques of membrane bound APP

Question 13

What are Ependymal Cells?

Answer 13

Ependylmal cells Line the central canal of spinal cord and ventricular system. They Function to Regulate circulation between cerebrospinal fluid (CSF) & interstitial space of CNS. They have Cilia which assist circulation of CSF and Have stem cells – progenitors of neuroblasts & glioblasts

Additional Functions

• –Choroid plexus epithelial cells
  
  • §Modified ependymal cells
  • §Form the choroid plexus
  • §Regulate CSF formation

Question 14

what are choroid plexus epithelial cells?

Answer 14

2. Modified ependymal cells
3. Form the choroid plexus
4. Regulate CSF formation

Question 15

what are schwann cells?

Answer 15

• •Found in the PNS
• –Abundant
• –Form myelin sheaths of PNS axons

(similar to oligodendrites but in PNS)

Question 16

what are satellite cells?

Answer 16

• –Surround cell bodies located in PNS ganglia
• –Role in metabolism of ganglion neurons

. Satellite cells Surround cell bodies located in PNS ganglia and are sort of the astrocytes of peripheral ganglia by providing structure to the ganglia and having a role in regulation of the metabolism of ganglionic neurons

Question 17

How do Schwann cells myelinate peripheral axons?

Answer 17

Schwann Cells myelinate peripheral axons by wrapping themselves around the axon. The repetitive layers of cell membrane is the lipid of myelin sheath

Question 18

How many schwann cells coat a single axon and what is the space between them called?

Answer 18

Thousands of Schwann cells will coat a single axon with the space between adjacent Schwann cells being the peripheral nodes of Ranvier

Question 19

What do MS and Guillain-Barre Syndrome have in common that relates to the material covered in this section?

Answer 19

Multiple Sclerosis & Guillain-Barre Syndrome are both Autoimmune disorder. In multiple sclerosis Proteins expressed by oligodendrocytes are erroneously recognized as foreign by immune system so you have Loss of myelin in brain and spinal cord. In Guillain-Barre Syndrome Proteins expressed by Schwann cells are erroneously recognized as foreign by immune system so you have Loss of myelin in the peripheral nervous system