Neurons and Glia Flashcards
What is the organization of the CNS?
brain, spinal cord, and neural portions of the eye
What is the organization of the PNS?
peripheral nerves, nerve endings, peripheral. nerve ganglia
What is the similarity between the CNS and PNS?
both have neurons and glia/supporting cells
What is the importance of glia?
needed for survival of neurons
What are the cells in the brain?
neurons, glia, endothelial cell (brain capillary), and ependymal cells (epithelial-like)
What are the types of glia?
astrocytes, oligodendrocytes, and microglia
What are the components of the neurons in the CNS?
dendrites, axon, oligodendrocyte, node of ranvier, and nissl bodies
What are the components of the neurons in the PNS?
schwann cells, myelin, motor and plate
What type of cells contribute to myelination?
schwann cells
What are the components of the cytoskeleton?
microtubules, centriole, actin (microfilament) and intermediate filaments
What are the membrane bound organelles?
lysosome, vesicle, golgi, mitochondrion, S and R ER, and peroxisome
What are the components of the nucleus?
nuclear membrane and nucleolus
Nissl bodies and lipofuscin pigment make up the …?
neuronal cell body (soma)
Ribosomes and rough ER make up what?
nissl bodies
Lipofuscin pigment is also known as…
“age pigment”
What is a lipofuscin pigment?
lysosomes with degradation products (residual body)
Nissle bodies stain … with …. dye
dark; basic
Dendrites are extensions of the …
cell soma; contains proteins and organelles
Dendrites do what to the surface area of neurons for reception?
increase surface area
Are dendrites myelinated?
NO
What are the characteristics of dendrites?
many of them, ramified, spiny, taper as branch
What are the characteristics of axons?
one, straight, NO spines, NO taper
To conduct action potential is the purposed of what?
axons
Do axons have nissl bodies or organelles?
NO
Can axons be myelinated?
YES
Bipolar, pseudounipolar, and multipolar are types of ….
neurons
What is a bipolar neuron?
single axon emerges from either side of the cell body
What is a pseudounipolar neuron?
single axon divides a short distance from the cell body
What is a multipolar neuron?
many dendrites and a single long axon emerge from the cell body
What are examples of a multipolar neuron?
pyramidal and purkinje cells
Neuron types are associated with what?
locations in the CNS or PNS
What are the unique properties of neurons?
- conduct electrochemical signals after impulses are received on the dendrites or cell body
- neurons possess unique connections between cells -> synapses
What is the direction of information flow in neurons?
dendrites -> soma -> axon -> synapse
Why are microtubules necessary?
important for neuron life
What are microtubules composed of?
tubulin proteins
Where are actin/microfilaments present?
in all cell types
What are actin/microfilaments composed of?
G (globular) and F (filamentous) actin
What is G actin?
free actin in cytoplasm
What is F actin?
polymerized actin of the filament
Which end of F actin fast growing?
plus end
Which end of F actin slow growing?
minus
What do actin/microfilaments aid with within the cell?
transport
What are the diameters of the parts of the cytoskeleton?
microtubules: 25 nm
actin/microfilaments: 5 nm
intermediate: 10 nm
What are intermediate filaments composed of?
neurofilament (light, medium, heavy)
What are intermediate filaments used for?
identification of tissues
What are the characteristics of intermediate filaments?
rope-like; heterogenous protein family (6 classes)
What is apart of class 3 family for intermediate filaments?
vimentin (most distributed IF tissue)
Vimentin is composed of ….
- glial acidic fibrillry protein -> astrocytes
- peripherin (peripheral nerve cells)
What is apart of class 4 family for intermediate filaments?
neurofilaments and nestin (nerve cells)
What are neurofilaments and where are they found?
neurofilament triplet proteins (L,H,M); in axons and dendrites of nerve cells
What is nestin and where can it be found?
neural stem cells; muscle cells
What are the two motor proteins?
kinesin and dynein
What type of transport does kinesin mediate?
anterograde: AWAY from the cell
What type of transport does dynein mediate?
retrograde: TOWARDS the cell/centrosome
What is the transport of neurotransmitter and their precursors?
anterograde
Which motor protein plays a role in ciliary and flagellar movement?
dynein
In axonal transport, where does anterograde travel? Fast or slow?
from soma to synapse; FAST
In axonal transport, where does retrograde travel? Fast or slow?
from synapse to soma; SLOW
Which axonal transport serves as a potential entry for harmful substances from periphery to neuronal cell body?
retrograde
What is the path of kinesin transport?
- organelles/vesicles attach to kinesin
- microtubule releases ADP
- kinesin moves along microtubule using ATP
What is the path of dynein transport?
- organelles/vesicles attach to dynein
- dynein moves along microtubule using ATP
- ADP is released
What are the types of synapses?
axosomatic, axoaxonic, axodendritic, and axospinous
What is an axosomatic synapse?
an axon terminal ending on the soma of a neuron
Which synapse is: an axon terminal contacting another axon terminal?
axoaxonic
Which synapse is: an axon terminal ending on a dendrite?
axodendritic synapse
What is an axospinous synapse?
an axon terminal facing a dendritic spine
Bergman glia allows for…
migration of neurons
What is Bergman glia?
functional interdependence of neuroglial cells and neurons during development
What are the types of astrocytes?
protoplasmic and fibrous
Where are protoplasmic astrocytes found?
in gray matter
What astrocyte is found in white matter?
fibrous
What glial cell is involved in myelination in the CNS?
oligodendrocytes
Where can oligodendrocytes be found?
in white matter; found in gray but role unknown
What is the function of astrocytes?
- nourishment of neurons
2.maintenance of neurons - protection of neurons
Astrocytes serve as what type of barrier?
blood-brain barrier
What is the only reservoir of glycogen in the brain?
astrocytes
What glial cell serves as an index of CNS toxicity?
astrocytes
How do astrocytes interconnect and outline the CNS?
- brain surface
- ependymal lining of ventricles
- synapses and blood vessels
- isolate synapses and nodes of ranvier
- surround foreign bodies in CNS
- form “glial scar” with high conc. of GFAP fibrils
How do astrocytes react to injury?
by increasing GFAP
Astrocytes form what type of junctions to permit cell transfer of small molecules/ions?
desmosomal (tight) and gap
Why do astrocytes form syncytium junctions?
allow diffusion of ions/small cytoplasmic molecules between adjacent astrocytes
What is the name of the gap junction protein?
connexin-43
What is the microglia life cycle?
- enter CNS and become ameboid microglia to clear debris during development
- blood-brain barrier closes; becomes quiescent microglia
- activated by injury/infection
What cells are the resident macrophages of the CNS?
phagocytic cells
What type of glia is the primary responder to injury of the brain?
microglia
What are examples of injuries microglia can respond to?
multiple sclerosis and trauma
What are the 2 markers of microglia?
complement receptor 3 and MHC-2
Microglial cells and astrocytes interact to modulate what?
immune responses
How does microglia react to CNS injury?
- after damage. become progressively activated
- severe activation causes macrophages to form
- inflammation can lead to damage of neurons
Myelin sheaths are synthesized by what?
oligodendrocytes
Oligodendrocytes can myelinate how many axons?
SEVERAL
What is the role of oligodendrocytes?
- wrap around axons of CNS neurons
- insulate axon and enhance speed of conduction of electrochemical impulses
How do Schwann cells play a role in the myelination process?
wraps around ONE axon
Schwann cells form….
myelin sheaths
Stimuli from multiple synapses sum at the…
axon hillock
What happens when a threshold is reached during impulse conduction?
an action potential (wave) is triggered
Where does the action potential (wave) travel?
DOWN the axon
What does the speed of the action potential depend on?
the diameter of the axon
What is saltatory conduction?
when nerve impulses “jump” from node to node
What are non-brain fenestrated capillaries?
have SMALL GAPS in plasma membrane of endothelial cells
What are brain non-fenestrated capillaries?
have TIGHT junctions between endothelial cells
How is the blood-brain barrier formed?
by endothelial cells with tight junctions and glial feet processed of astrocytes
Why do astrocytes induce capillaries?
to form zonula occludens to limit diffusion of small molecules
Ependymal cells line what surface?
inner surface of brain ventricles
What are the functions of ependymal?
- movement of CSF
- bidirectional transport of materials between CSF and neuropil
Where can ependymal cells be modified within to produce CSF (part of choroid plexus)?
ventricles
What makes up the volume of the brain?
half is neurons; Other half is neuroglia/glia
