Figure 9.

Fate maps of Ca²⁺ entering spines #37 and #52 in response to EPSP+bAP. The fate of all Ca²⁺ entering the spines was tracked for 100 ms after the stimulus. While inside the spine, Ca²⁺ can diffuse freely (blue) or bind to Ca²⁺-binding proteins and pumps (yellow). To restore the resting state, Ca²⁺ that enters is removed from the spine by PMCA pumps (red), NCX exchangers (white), or via diffusion through the spine neck (green) as free Ca²⁺ or while bound to mobile calbindin. (A,C,E) Fate of Ca²⁺ in median-size spine #37; (A) after a bAP in the absence of calbindin, (C) a bAP in the presence of calbindin, or (E) an EPSP+bAP in the presence of calbindin. (B,D,F) Fate of Ca²⁺ in large spine #52; (B) after a bAP in the absence of calbindin, (D) a bAP in the presence of calbindin, or (F) an EPSP+bAP in the presence of calbindin. Data is represented as a fraction of the total Ca²⁺ influx. The actual number of Ca²⁺ ions tracked is indicated in the y-axis label.