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How do astrocytes help maintain a stable environment around neurons?
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nervous system
In a myelinated axon, the myelin sheath prevents the local current (small black arrows) from flowing across the membrane. This forces the current to travel down the nerve fibre to the unmyelinated nodes of Ranvier, which have a high concentration of ion channels. Upon stimulation, these ion channels propagate the action potential (large green arrows) to the next node. Thus, the action potential jumps along the fibre as it is regenerated at each node, a process called saltatory conduction. In an unmyelinated axon, the action potential is propagated along the entire membrane, fading as it diffuses back through the membrane to the original depolarized region.
Astrocytes are star-shaped neuroglia that play a vital role in maintaining a stable environment for neurons within the central nervous system.1
They contribute to this stability through several key functions:
- Modulation of Synaptic Transmission: Astrocytes possess high-affinity uptake systems for neurotransmitters, such as glutamate and gamma-aminobutyric acid (GABA). By removing these chemicals from the synapses, astrocytes terminate neurotransmitter action, preventing overstimulation and ensuring precise signaling.1
- Neurotransmitter Storage: Beyond clearing synapses, these cells may act as storage systems, holding neurotransmitters for future release when needed.1
- Structural and Vascular Support: Astrocytes extend processes that form expansions and end feet at the surfaces of vascular capillaries, which helps regulate the local environment.1
- Response to Injury: Following damage to the nervous system, astrocytes divide and occupy the spaces left by injured neurons, helping to maintain the structural integrity of the tissue.1