Exam 2 Lecture - Neuroglia Flashcards
Where are ependymal cells located?
in the CNS
What do the ependymal cells surround?
the central canal of the spinal cord and ventricle
What is the structure of the ependymal cells?
- cuboidal to columnar cells
- the apical surface is lined with cilia
What are the functions of the ependymal cells?
assist with CSF circulation
form the choroid plexus
What are choroid epithelium?
modified ependymal cells - microvilli
What is the function of the choroid epithelium?
in charge of CSF production
What is the most abundant neuroglia of the CNS?
astrocytes
Where are astrocytes located?
the CNS
What are the functions of astrocytes?
- respond to injury- proliferate to form scar tissue
- Maintain optimal CNS environment
How do astrocytes maintain optimal CNS environment?
- induct and maintain capillary endothelium as the blood brain barrier
- help transport glucose to neurons
- store glycogen
- promote neuronal survival
- prevent glutamate neurotoxicity
What does the choroid epithelium create?
the blood-csf barrier
How does the choroid epithelium prevent leakage in between cells?
tight junctions
What is the choroid plexus made up of?
choroid epithelium and connective tissue
What is the connective tissue of the choroid plexus composed of?
fenestrated capillaries
How is the capillary tight junction formed and maintained?
Via the glial cell line-derived neurotropic factor (GDNF) that is released by astrocytes
What is the function of the CSF?
- provides physical support of the CNS
- maintains the chemical environment of the CNS
- regulates intracranial pressure
How does the CSF maintain the chemical environment of the CNS?
it removes metabolites for optimal extracellular fluid
How does CSF regulate the intracranial pressure?
- the CSF and blood volume vary inversely
- an increase in CSF absorption leads to a decrease in CSF production
How do capillary endothelium function (blood brain barrier) with the blood and CNS tissue?
regulate the exchange of solutes between the layers
If something wants to enter or leave the blood brain barrier, what does it need to go through?
the wall of the capillary
Through what processes does the blood brain barrier regulate the exchange of solutes between the blood and CNS tissue?
- diffusion
- transportation (carrier mediated)
What does the blood brain barrier diffuse across the cell?
water, gasses, lipophilic substances (alccohol, nicotine, heroin, cyanide)
What does the blood brain barrier use carrier mediated transport for?
- amino acids if they are not synthesized in the brain
- vitamins
What amino acids are normally transported across the blood brain barrier?
Large neutral amino acids
What is tyrosine changed into in the brain?
catecholamine
What is tryptophan changed into in the brain?
serotonin
What amino acids are normally not transported across the blood brain barrier?
small neutral amino acids
Where are microglia located?
CNS
What is the function of microglia?
once activated, they respond to tissue damage and remove debris by phagocytosis
Where are oligodendrocytes located?
CNS
What is the function of oligodendrocytes?
increase conduction by myelinating axons that are 1 micro meter or greater
Where are schwann cells located?
PNS
What is the function of schwann cells?
- increase conduction velocity by myelinating axons
- Also support axons under 1 micrometer, but do not myelinate
What is the process of myelination?
- cell processes elongate and encircle the axon
- one process starts wrapping the plasma membrane around the axon
What is the difference between myelinated and non-myelinated axons?
myelinated axons are larger and conduct impulses quickly
non-myelinated axons are small and slowly conduct impulses
What is a nerve fiber composed of?
axon and schwann cells
What is the connective tissue of a nerve fiber?
endoneurium
What is a fascicle composed of?
nerve fibers
What is the connective tissue of the fascicle?
perineurium
What are multiple fascicles considered?
a nerve
What is the connective tissue of the nerve?
epineurium
