Glial Cells Flashcards
Microglia (4)
Explain what they are known as + spatial organization/location + origin + what are they constantly doing?
- Are the resident macrophages/immune cells of the brain.
- They tile whole brain and spinal cord like other glia
- Uniqe developmental origin: Microglia are of myeloid origin and migrate into the develping CNS fom the yoke sac at approximately embryonic day 10. All other brain cells come from the neural tube/ectoderm
- Constantly surveying the tissue for damaged cells, plaques and infectious agents
Explain BBB and WBC
If the BBB breaks down due to really bad problems then WBC (immune cells) can get in but usually, dont. Microglia are usually already in brain.
Ramified/resting state
In this state, microglia extend long, highly branched processes that continuously scan the surrounding brain tissue for changes in the microenvironment. While their processes are highly dynamic and move constantly, their somata (cell body) remain stationary and do not migrate. This state allows microglia to detect signs of infection, injury, or changes in neural activity and respond accordingly.
Microglia and neuron activity
Microglia can detect high neurnal activity (high burst of LTP) and increase their motility in response.
Microglia can become more permantely hyper-ramified after:
plasticity
Microglia and when there are problems in the brain (3):
state + activated by + secrete
- Resting ramified state into more amoeboid/activated state
- Microglia are activated by: glutamate, K+, ATP (necrosis factors), pro-inflammatory cytokines and LPS (cell wall component of gram-negative bacteria) cell apotosis can cause this
- Once activated they secrete pro-inflammatory signals such as IL-alpha, IL-beta as well as TNF-alpha. They can also express immuno-molecules for incomming T-cells when the BBB becomes compromised.
Microglia
Over short distances, microglia can extend their processes to become activated and ———. When they need to move a relatively large distance in order to scavenge, or there are persistent problems in the tissue, they ——-.
- phagocytose without moving their soma
- retract their processes and they enter into an amoeboid state
Microglia states in the human brain (4):
Microglia and laser lesion experiment:
- If you use a laser and lesion the brain area, microglia will sense this and start polarizing processes towards lession site and push through the tissue to chase after lesion site. It will then encapsulate and seal it off and eat cell debris.
Synapse elimination experiment:
Theres hyperwiring in the begining (more connections when you are small. In adults and when you grow brain eliminates uncessary connections. In this experiment you look at the retinal expanding to the lateral geniculate. Incomming sensory from each eye crosses over to each side. You colour one side cell red and one side blue. Most of them cross athe the LGN but not all so you will still find some red synapse at the left even though they start at the left and mostly cross to the right. Early in development (P5) there are bits of red and blue in the microglia. They are eating these things. Much later in time when LGN trimmed up it’s neural circuit, you find there are very few engulfment in the microglia.
Synapse pruning involves the complement cascade
- SYnapse express complement cascade component 3 when it doesnt want to had around anymore.
Microglia comes by and has receptor C3R for the component 3 and binds to phasgocytose. - You can knock out the C3R or C3 gene and you will greatly reduce the microglia’s ability to eat these synapses.
Oligodendrocytes (3)
What doesx2 + allows for
- Myelin forming cell can provide segment for multiple neuron cell
- Fast long-distance electrical communication
- A type of glial cell that provide myelin, metabolic and trophic support (GDNF, BDNF) for neurons/axons
Oligodendrocyte progenitor cells
% + Express + presursor + dont havve + receive
- 4% of the cells in the gray matter of the brain
- Express the proteoglycan NG2 marker (no other cell has this)
- Are a precursor cell that can differentiate into a mature myelinating oligodendrocyte
- They dont have to differentiate and many exist into adulthood. The reason is that if an OPC developes into a mature oligodendrocyte, a neighbouring OPC will divide and replace it keeping their numbers constant.
- They do not fire AP but do receive both inhibitory and excitatory synaptic transmission. Only glia to recieve direct synaptic contact from neurons.
Synaptic inputs are used by OPcells to
decide if it wants to mature or not and start myelinating
What occurs as a OPC/NG2 cell differentiates?
