Figure 1: (A) Calcium-induced-calcium-release in a dendritic spine. The first Ryanodine Receptor (RyR) at the base of the spine apparatus that opens is triggered by the fastest calcium ion. An avalanche of calcium release ensues by opening the neighboring receptors. This leads to rapid amplification at a much shorter time than the MFPT of the diffusing calcium ions. (B) Activation of calcium release by IP3 receptors, which are calcium channels gated by IP3 molecules, which function as secondary messengers. When the first IP3 molecules arrives at the first IP3R, its calcium release induces an avalanche due to the opening of subsequent IP3 receptors. (C) In the post-synaptic terminal, the influx of ions due to the opening of NMDA/AMPA receptors is the amplification process. The signal of the pre-synaptic signal transmitted by the neurotransmitter molecules diffusing in the synaptic cleft and the time scale of the amplification are determined by the fastest molecules that arrive at the receptor targets and open them.
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