Calcium modeling of spine apparatus-containing human dendritic spines demonstrates an “all-or-nothing” communication switch between the spine head and dendrite
Fig 5
Effects of active SA with RyR calcium exchange mechanisms only.
These plots were generated with active SA with only RyR. Plots in row A show the calcium concentration traces in the head and dendrite at the critical RyR density. Plots in row B show the calcium concentration traces at sub-critical (5% below critical) RyR density. It is worth observing that Ca2+ coupling is significantly decreased. In Fig 5C, 5D, and 5E, we demonstrate for spine 8 that there is a critical RyR density such that Ca2+ coupling occurs in the dendritic region. The RyR density parameter is incremented in 0.01 μm−2 steps. The maximum [Ca2+] in the dendritic region has a significant jump at ≈ 3.50 μm−2, please also see the supplemental video showing an accumulation of calcium in the spine region; however, at critical RyR density calcium is propagated to the dendritic region. For plot D we performed the same RyR density increment experiments but with different Ca2+ influx at the synapse. For all spine simulations (rows A and B) we used a fixed Ca2+ influx at the synapse.