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What are the 3 categories of nervous system cells?
- nonneuroglial
- neuroglial
- neurons
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Do nonneuroglial cells produce AP?
no, non impulse transmitting
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Do the nonneuroglial cells add structural support to the brain like other glial cells?
no, non-supporting
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What kind of cell bodies do nonneuroglial cells have?
small cell bodies
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Nonneuroglial cell embryonically form from:
ectoderm
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What are nonneuroglial cells collectively called?
ependymal
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The ependymal constitutes what?
choroid plexus
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Where is the ependymal located?
in ventricular system
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What does the ependymal line?
roof of ventricle system of the brain
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What is the function of ependymal?
to produce cerebrospinal fluid (CSF)
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What is the ependymal?
collection of nonneuroglial cells
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Do neuroglial cells produce AP?
no, non-impulse transmitting
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Where are neuroglia cells found?
in both CNS and PNS, located in spaces not occupied by blood vessels and neurons
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Which are more abundant? Neuroglia cells or neurons?
neuroglia (5-50x) depending on where they are located
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Are neuroglial cells involved w/ synapse transmission of AP?
no
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What are neuroglial cells also called?
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What are the functions of neuroglia?
- acts as connective tissue for brain, providing structural support
- carry nutrients to neurons, whatever released can get into neuron
- clean cellular debris after inflammatory process/infection
- myelinate (insulate) neurons
- provide chemical signals that influence neurons in terms of neural development and migration to target sites
- synapse formation (allows neurons to talk to one another)
- blood brain barrier (filtering system)
- gliosis
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What is gliosis?
scar formation in the brain, tumors may form from this scar tissue--glioma
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Are glial cells mitotic?
yes
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What are the 4 types of neuroglial (glial) cells?
- astrocytes
- oligodendrocytes
- schwann cells
- microglia
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What is another name for astrocytes?
macroglia
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What are astrocytes?
star-shaped glial cells w/ long cellular processes
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What are the 2 types of astrocytes?
- fibrous astrocytes
- protoplasmic astrocytes
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Where are fibrous astrocytes found?
white matter
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What are the functions of fibrous astrocytes?
- primary supporting cells in the nervous system
- forms scar tissue
- limited involvement in phagocytosis
- strongly involved w/ metabolic support for neurons
- involved in developmental processes during embryonic processes
- releases chemicals involved in destruction of synapses during normal embryonic development
- provide transient (temporary) scaffolding (pathway) to developing neurons during gestation
- form blood brain barrier
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Are the fibrous astrocytes processes fewer or greater in number compared to protoplasmic astrocytes?
fewer
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Are the fibrous astrocytes shorter or longer than the protoplasmic astrocytes?
longer
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Are the fibrous astrocytes more wavy or straighter than protoplasmic astrocytes?
straighter
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Are fibrous astrocytes involved in phagocytosis and immunity?
limited involvement but usually not involved in phagocytosis
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Are fibrous astrocytes involved w/ metabolic support for neurons?
yes, strongly
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What is metabolic support for neurons?
regulate ionic environment around neurons by using 'end feet' (foot like structures)
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How are fibrous astrocytes involved in developmental processes during embryonic processes?
inhibit or promote outgrowth of neuronal cellular processes during neural (embryonic) development by synthesizing and releasing trophic and adhesion molecules (allowing NS to grow)
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Why do fibrous astrocytes release chemicals involved in the destruction of synapses during normal embryonic development?
because we overproduce neurons (to get from 3 trillion neurons to 100 billion)
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Why do fibrous astrocytes provide transient scaffolding to developing neurons during gestation?
enable neurons to migrate and allow them to know where to go
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Blood brain barrier:
- links between capillaries and neurons of the brain
- specialized barrier formed by endothelial cells and astrocytes which prevents large proteins and charged molecules from entering CNS
- you do not want blood in the brain tissue b/c it will mess up the system
- controls the passage of molecules b/w the capillaries and the neurons
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endothelial cells:
line capillaries and mediate diffusion of substances from blood directly into interstitial fluid (in reference to brain tissue)
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Where are the 'end feet' on astrocyte processes?
cover most of capillary surfaces
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What do the astrocyte processes' end feet do?
influence passage of substances b/w capillaries and neurons of the brain
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What can go through the blood brain barrier?
- glucose
- oxygen
- electrolytes
- insulin
- thyroxin
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What can't go through the blood brain barrier?
- molecules that are too big
- serum proteins (i.e., albumin) causes brain swelling=death if compression is not relieved
- penicillin (can't be used to treat brain infection)
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Where are protoplasmic astrocytes found?
grey matter
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Are the protoplasmic astrocytes more numerous or less numerous than fibrous astrocytes?
more numerous
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Are the protoplasmic astrocytes thicker or thinner than fibrous astrocytes?
thicker
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Are protoplasmic astrocytes longer or shorter than fibrous astrocytes?
shorter
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Are protoplasmic astrocytes more branched or less branched than fibrous astrocytes?
more branched
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Which of the two types of astrocytes are more metabolically active?
bibrous astrocytes
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What is the primary function of protoplasmic astrocytes?
- isolate receptive surfaces of neurons:
- separating/insulating neurons
- reduces random flow of neuronal activity
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What is another name for oligodendrocytes?
macroglia
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Are oligodendrocytes bigger or smaller than astrocytes?
smaller, they have a small, rounded cell body)
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Which type of cell is the most numerous in the CNS?
oligodendrocytes
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Where are oligodendrocytes found?
- only in CNS
- white matter of brain and SC
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Do oligodendrocytes have a small or large number of cellular processes?
small
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What is the primary function of oligodendrocytes?
- myelinate neurons in CNS to provide insulation
- must produce myelin
- forms concentric layers of myelin (laminated)
- typically myelinate more than one axon of a neuron, but no more than 4
- only mylinate a portion of the axon; each axon could have 10 oligodendrocytes myelinating it
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myelin:
a phospholipid (responsible for the white color)
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Multiple Sclerosis
destruction of myelin resulting in shorting out/overactivity
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What is another name for Schwann cells?
macroglia
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Where are schwann cells found?
PNS
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Which other neuroglial cells are schwann cells similar to?
oligodendrocytes (but schwann cells are in the PNS)
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What is the function of schwann cells?
myelinate cellular processes of neurons in PNS to laminate neurons for insulation
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What percent of glial cells do the microglia constitute?
10%
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Where do microglia live?
only in CNS
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Are microglia active during normal brain functioning?
no, they are inactive
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What do microglia cells do in a normal brain (non-pathological)?
maintain synaptic integrity via nutrition and structural support
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Microglia are normally dormant, so what would cause them to be activated?
disease/infection
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Do microglia have a low or high threshold?
low
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When microglia are activated, what happens?
- they proliferate and migrate to pathogen and they produce antibodies
- perform immune function
- phagocytose bacteria (surround and kill) via enzymatic digestion
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What immune function does the microglia perform?
produce antibodies
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Poor microglial cell function (leading to high number of microglia cells) is implicated in what types of dieseases?
- general dementia
- Alzheimer's
- Parkinson's
- schizophrenia
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What are microglia cells a product of?
mesoderm
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All other neuroglial cells (except microglia) are products of what?
ectoderm
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