Figure 1. pH regulation by glial cells. Diagram of an astrocyte illustrating the main mechanisms involved in pH regulation. The three major regulatory mechanisms are the Na⁺/H⁺ exchanger, the Cl^–/HCO₃^– exchanger and the enzyme carbonic anhydrase (CA) that converts carbon dioxide into HCO₃^–. Adapted from Deitmer and Rose (1996).

Figure 2. The tripartite synapse. By sending processes around the two neuronal elements of the synapse (left panel), astrocytes are ideally positioned to participate actively in synaptic transmission. Once neurotransmitters are released in the synaptic cleft (1), the postsynaptic neuron and the astrocyte process detect this synaptic signal through the binding of neurotransmitters on receptors (2). Then, the subsequent increase in calcium, in the astrocytes (3) induces release of gliotransmitters (4) in the synaptic cleft to modulate synaptic transmission (5) and neuronal excitability (6).

Figure 3. Mechanisms of Ca²⁺ waves. Diagram illustrating the mechanisms involved in the production of the glial Ca²⁺ waves. Upon activation by glutamate, an elevation in inositol trisphosphate (IP₃) production causing the release of Ca²⁺ from internal stores will lead to the release of adenosine trisphosphate (ATP) by the astrocyte. The ATP will activate purinergic receptors of neighbour astrocytes, causing an elevation of Ca²⁺ and an additional release of ATP, which will extend further on to additional astrocytes. There is also evidence that IP₃ could pass through gap junctions from astrocytes to astrocytes.